1st commit

README.md

@@ -0,0 +1,17 @@
+
+## Install
+
+Make sure to [download the loVR runtime](https://lovr.org/downloads) and drag
+the `src`-folder of this repository to the **lovr** application [as described in the docs](https://lovr.org/downloads)
+
+If you already have lovr installed, you can run this in your console as well:
+```
+$ ./lovr src
+```
+
+or nix:
+
+```
+$ appimage-run ./lovr src
+```
+

src/browser.lua

@@ -0,0 +1,24 @@
+local browser = {}
+
+browser.to = function(url,refererer)
+  print("surfing to " .. url)
+  local URL = api.url.parse(url) 
+  foreach( api.protocol, function(name, p)
+    if URL.protocol:match("^"..name) then 
+      protocol = p
+    end
+  end)
+  if protocol then
+    local status, data, headers = protocol.request(url)
+    local ctx = {
+      succes  = (status >= 200 and status < 300),
+      status  = status,
+      data    = data,
+      headers = headers, 
+      URL     = URL
+    }
+    api.exec( api.ext, 'renderURI', ctx )
+  end
+end
+
+return browser

src/conf.lua

@@ -0,0 +1,8 @@
+package.path = package.path .. ';' .. 
+               arg[0] .. '/lovr/?.lua;' .. 
+               arg[0] .. '/lovr/?/init.lua;' .. 
+               arg[0] .. '/lib/?.lua'
+
+if lovr ~= nil then 
+  require("lovr/conf")
+end

src/ecs.lua

@@ -0,0 +1,37 @@
+local api = ...
+local ecs = require("tiny-ecs")
+
+ecs.initers = {
+  renderer = function()
+    local renderer = ecs.processingSystem()
+    renderer.filter = ecs.requireAll('type') -- *TODO* might need filter later
+    function renderer:process(obj, pass)
+      local type = obj:type()
+      if type == "Model" then 
+        pass:setMaterial()
+        pass:setCullMode('none')
+        pass:draw(obj, 0, 0, 0, 1, 0, 1, 0, 0, 1)
+      end
+    end
+    ecs.addSystem( ecs.world, renderer )
+  end
+}
+
+ecs.enabled = true
+ecs.world   = ecs.world()
+ecs.world.update = ecs.update -- swap with extension update-func  
+
+ecs.init = function()
+  ecs.initers.renderer()
+end
+  
+ecs.update = function(dt)
+  --ecs.world.update( ecs.world, dt ) -- *TODO* different filter
+end
+
+ecs.draw = function(pass)
+  local opts = {
+  ecs.world.update( ecs.world, pass )
+end
+
+return ecs

src/ext/gltf/main.lua

@@ -0,0 +1,27 @@
+local api = ...
+
+local gltf = {
+  name = "gltf",
+  enabled = true,
+
+  init = function() end,
+
+  renderURI = function(ctx)
+    local URL = ctx.URL
+    local me  = api.ext.gltf
+    if ctx.succes and URL.extension == 'GLB' or URL.extension == 'GLTF' then
+      local model = api.graphics.newModel( api.data.newBlob(ctx.data) )
+      local ecs   = api.ecs
+      ecs.add( ecs.world, { 
+        x = 0,
+        y = -7,
+        z = 0,
+        model = model 
+      })
+
+    end
+  end
+
+}
+
+return gltf

src/ext/kitchensink/main.lua

@@ -0,0 +1,84 @@
+local api = ...
+    
+local sample = require "sample"
+
+return {
+  name = "kitchensink",
+  enabled = true,
+
+  init = function() end,
+
+  update = function()
+    local iui = api.iui
+    local backend = api.backend 
+    local mainWindow = api.mainWindow
+
+    sample.main()
+
+  end,
+
+  load = function()
+    local iui = api.iui
+    local backend = api.backend 
+    local mainWindow = api.mainWindow
+
+    sample.load({
+        gameSunsetImage = lovr.graphics.newTexture(
+            "lovr/sample/assets/game-sunset.png", {}
+        ),
+        nineSliceImage = {
+            image = lovr.graphics.newTexture(
+                "lovr/sample/assets/ui-box-slice.png", { mipmaps = false }
+            ),
+            l = 8,
+            t = 8,
+            r = 8,
+            b = 8
+        },
+        smileMSDFLayeredImage = {
+            {
+                image = lovr.graphics.newTexture(
+                    "lovr/sample/assets/smile-bg.png",
+                    { linear = true, mipmaps = false }
+                ),
+                color = iui.newColor(0.944, 0.794, 0.468)
+            },
+            {
+                image = lovr.graphics.newTexture(
+                    "lovr/sample/assets/smile-fg.png",
+                    { linear = true, mipmaps = false }
+                ),
+                color = iui.newColor(0.157, 0.157, 0.157)
+            }
+        },
+        nineSliceMSDFLayeredImage = {
+            {
+                image = {
+                    image = lovr.graphics.newTexture(
+                        "lovr/sample/assets/nine-slice-interior.png",
+                        { linear = true, mipmaps = false }
+                    ),
+                    l = 16,
+                    t = 24,
+                    r = 16,
+                    b = 24
+                },
+                color = iui.newColor(0.337, 0.653, 0.939)
+            },
+            {
+                image = {
+                    image = lovr.graphics.newTexture(
+                        "lovr/sample/assets/nine-slice-frame.png",
+                        { linear = true, mipmaps = false }
+                    ),
+                    l = 16,
+                    t = 24,
+                    r = 16,
+                    b = 24
+                },
+                color = iui.newColor(0.258, 0.300, 0.572)
+            }
+        }
+    })
+  end
+}

src/ext/startupscene/main.lua

@@ -0,0 +1,103 @@
+local api = ...
+local envTex
+local skybox
+local environmentMap
+local sphericalHarmonics
+local shader
+    
+return {
+  name = "startupscene",
+  enabled = true,
+
+  init = function() end,
+
+  update = function()
+    local iui = api.iui
+    local backend = api.backend 
+    local mainWindow = api.mainWindow
+  end,
+
+  load = function()
+    --if api.iui.idiom == "vr" then
+      envTex = lovr.graphics.newTexture("lovr/assets/img/env.png", {})
+      skybox = lovr.graphics.newTexture({
+        px = 'ext/startupscene/skybox/Dayright.jpg',  -- 'px.png',
+        nx = 'ext/startupscene/skybox/Dayleft.jpg',   -- 'nx.png',
+        py = 'ext/startupscene/skybox/Daytop.jpg',    -- 'py.png',
+        ny = 'ext/startupscene/skybox/Daybottom.jpg', -- 'ny.png',
+        pz = 'ext/startupscene/skybox/Dayfront.jpg',  -- 'pz.png',
+        nz = 'ext/startupscene/skybox/Dayback.jpg'    -- 'nz.png'
+      })
+      environmentMap = lovr.graphics.newTexture('ext/startupscene/skybox/ibl.ktx')
+
+      sphericalHarmonics = lovr.graphics.newBuffer({ 'vec3', layout = 'std140' }, {
+        {  0.611764907836914,  0.599504590034485,  0.479980736970901 },
+        {  0.659514904022217,  0.665349841117859,  0.567680120468140 },
+        {  0.451633930206299,  0.450751245021820,  0.355226665735245 },
+        { -0.044383134692907, -0.053154513239861, -0.019974749535322 },
+        { -0.053045745939016, -0.057957146316767, -0.011247659102082 },
+        {  0.485697060823441,  0.490428507328033,  0.397530466318130 },
+        { -0.023690477013588, -0.024272611364722, -0.021886156871915 },
+        { -0.179465517401695, -0.181243389844894, -0.141314014792442 },
+        { -0.144527092576027, -0.143508568406105, -0.122757166624069 }
+      })
+      shader = lovr.graphics.newShader([[
+        vec4 lovrmain() {
+          return DefaultPosition;
+        }
+      ]], [[
+        uniform textureCube cubemap;
+        uniform sphericalHarmonics { vec3 sh[9]; };
+
+        vec4 lovrmain() {
+          Surface surface;
+          initSurface(surface);
+
+          vec3 color = vec3(0);
+          vec3 lightDirection = vec3(-1, -1, -1);
+          vec4 lightColorAndBrightness = vec4(1, 1, 1, 3);
+          float visibility = 1.;
+          color += getLighting(surface, lightDirection, lightColorAndBrightness, visibility);
+          color += getIndirectLighting(surface, cubemap, sh);
+
+          return vec4(color, 1);
+        }
+      ]], {
+        flags = {
+          glow = true,
+          normalMap = true,
+          vertexTangents = false, -- DamagedHelmet doesn't have vertex tangents
+          tonemap = true
+        }
+      })
+    --end
+  end,
+
+  draw = function(pass)
+    if api.iui.idiom == "vr" then
+        -- skybox
+        pass:setCullMode('back')
+        pass:setBlendMode()
+        pass:skybox(skybox)
+
+        pass:setColor(1, 1, 1)
+        pass:setMaterial(envTex)
+        pass:draw(envTex, 0, 0, 0, 512, math.pi * 0.5, 1, 0, 0)
+
+        -- floor
+        --pass:setMaterial()
+        pass:setCullMode('front')
+        pass:setBlendMode('alpha')
+        pass:setMaterial()
+        pass:setColor(0.8,0.8,0.8,1)
+        pass:plane(0, 0, 0, 500, 500, math.pi * 0.5, 1, 0, 0, "fill", 5, 5)
+        pass:setColor( 0, 0, 0, 0.75 )
+        pass:plane(0, 0.01, 0, 500, 500, math.pi * 0.5, 1, 0, 0, "line", 100, 100)
+  
+        pass:setShader(shader)
+        pass:send('cubemap', environmentMap)
+        pass:send('sphericalHarmonics', sphericalHarmonics)
+
+    end
+  end
+}

src/ext/xrfragments/main.lua

@@ -0,0 +1,60 @@
+local api = ...
+local xrf
+
+return {
+  enabled = true,
+  init = function()
+    -- create a (ecs) system which detects add/remove entities
+    local ecs = api.ecs
+    xrf = ecs.system({
+
+      filter = ecs.filter('x&y&z'),
+
+      onAdd = function(self,obj)
+        function scanHrefs()
+          local tree = api.json.decode( obj['model']:getMetadata() )
+          api.util.traverse( tree['nodes'], function(obj)
+            if obj['extras'] ~= nil then 
+              if obj['extras']['href'] ~= nil then
+                print(obj['name'] .. ".href => " .. obj['extras']['href'] )
+                
+                -- create collider 
+                -- The "trick" is to set collider:setUserData on creation, to something unique that will act as some sort of identifier for your object. So when a hit is detected from world:raycast you get to know which object this collider is attached to. Hope it makes sense!
+
+                --To achieve this in Lua, you can create a metatable that uses the __newindex metamethod to intercept assignments to the table's fields. Whenever x is updated, the onUpdate function will be called with the table itself as the argument.
+                --Here's how you can implement it:
+                --
+                --
+                --foo = { x = 0, y = 0, z = 0, onUpdate = function(self) print("Updated!") end }
+                --
+                ---- Create a metatable
+                --local mt = {
+                --    __newindex = function(t, key, value)
+                --        rawset(t, key, value) -- Set the value
+                --        if key == "x" then
+                --            t.onUpdate(t) -- Call onUpdate if x is updated
+                --        end
+                --    end
+                --}
+                --
+                ---- Set the metatable for foo
+                --setmetatable(foo, mt)
+
+              end
+            end
+          end)
+        end
+        if obj['model'] ~= nil then 
+          pcall(scanHrefs)
+        end
+      end
+
+      onRemove = function(self,obj)
+
+      end
+
+    })
+    ecs.addSystem( ecs.world, xrf )
+
+  end
+}

src/lib/json.lua

@@ -0,0 +1,386 @@
+--
+-- json.lua
+--
+-- Copyright (c) 2020 rxi
+--
+-- Permission is hereby granted, free of charge, to any person obtaining a copy of
+-- this software and associated documentation files (the "Software"), to deal in
+-- the Software without restriction, including without limitation the rights to
+-- use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+-- of the Software, and to permit persons to whom the Software is furnished to do
+-- so, subject to the following conditions:
+--
+-- The above copyright notice and this permission notice shall be included in all
+-- copies or substantial portions of the Software.
+--
+-- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+-- IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+-- FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+-- AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+-- LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+-- OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+-- SOFTWARE.
+--
+
+local json = { _version = "0.1.2" }
+
+-------------------------------------------------------------------------------
+-- Encode
+-------------------------------------------------------------------------------
+
+local encode
+
+local escape_char_map = {
+  [ "\\" ] = "\\",
+  [ "\"" ] = "\"",
+  [ "\b" ] = "b",
+  [ "\f" ] = "f",
+  [ "\n" ] = "n",
+  [ "\r" ] = "r",
+  [ "\t" ] = "t",
+}
+
+local escape_char_map_inv = { [ "/" ] = "/" }
+for k, v in pairs(escape_char_map) do
+  escape_char_map_inv[v] = k
+end
+
+
+local function escape_char(c)
+  return "\\" .. (escape_char_map[c] or string.format("u%04x", c:byte()))
+end
+
+
+local function encode_nil(val)
+  return "null"
+end
+
+
+local function encode_table(val, stack)
+  local res = {}
+  stack = stack or {}
+
+  -- Circular reference?
+  if stack[val] then error("circular reference") end
+
+  stack[val] = true
+
+  if rawget(val, 1) ~= nil or next(val) == nil then
+    -- Treat as array -- check keys are valid and it is not sparse
+    local n = 0
+    for k in pairs(val) do
+      if type(k) ~= "number" then
+        error("invalid table: mixed or invalid key types")
+      end
+      n = n + 1
+    end
+    if n ~= #val then
+      error("invalid table: sparse array")
+    end
+    -- Encode
+    for i, v in ipairs(val) do
+      table.insert(res, encode(v, stack))
+    end
+    stack[val] = nil
+    return "[" .. table.concat(res, ",") .. "]"
+
+  else
+    -- Treat as an object
+    for k, v in pairs(val) do
+      if type(k) ~= "string" then
+        error("invalid table: mixed or invalid key types")
+      end
+      table.insert(res, encode(k, stack) .. ":" .. encode(v, stack))
+    end
+    stack[val] = nil
+    return "{" .. table.concat(res, ",") .. "}"
+  end
+end
+
+
+local function encode_string(val)
+  return '"' .. val:gsub('[%z\1-\31\\"]', escape_char) .. '"'
+end
+
+
+local function encode_number(val)
+  -- Check for NaN, -inf and inf
+  if val ~= val or val <= -math.huge or val >= math.huge then
+    error("unexpected number value '" .. tostring(val) .. "'")
+  end
+  return string.format("%.14g", val)
+end
+
+
+local type_func_map = {
+  [ "nil"     ] = encode_nil,
+  [ "table"   ] = encode_table,
+  [ "string"  ] = encode_string,
+  [ "number"  ] = encode_number,
+  [ "boolean" ] = tostring,
+}
+
+
+encode = function(val, stack)
+  local t = type(val)
+  local f = type_func_map[t]
+  if f then
+    return f(val, stack)
+  end
+  error("unexpected type '" .. t .. "'")
+end
+
+
+function json.encode(val)
+  return ( encode(val) )
+end
+
+-------------------------------------------------------------------------------
+-- Decode
+-------------------------------------------------------------------------------
+
+local parse
+
+local function create_set(...)
+  local res = {}
+  for i = 1, select("#", ...) do
+    res[ select(i, ...) ] = true
+  end
+  return res
+end
+
+local space_chars   = create_set(" ", "\t", "\r", "\n")
+local delim_chars   = create_set(" ", "\t", "\r", "\n", "]", "}", ",")
+local escape_chars  = create_set("\\", "/", '"', "b", "f", "n", "r", "t", "u")
+local literals      = create_set("true", "false", "null")
+
+local literal_map = {
+  [ "true"  ] = true,
+  [ "false" ] = false,
+  [ "null"  ] = nil,
+}
+
+
+local function next_char(str, idx, set, negate)
+  for i = idx, #str do
+    if set[str:sub(i, i)] ~= negate then
+      return i
+    end
+  end
+  return #str + 1
+end
+
+
+local function decode_error(str, idx, msg)
+  local line_count = 1
+  local col_count = 1
+  for i = 1, idx - 1 do
+    col_count = col_count + 1
+    if str:sub(i, i) == "\n" then
+      line_count = line_count + 1
+      col_count = 1
+    end
+  end
+  error( string.format("%s at line %d col %d", msg, line_count, col_count) )
+end
+
+
+local function codepoint_to_utf8(n)
+  -- http://scripts.sil.org/cms/scripts/page.php?site_id=nrsi&id=iws-appendixa
+  local f = math.floor
+  if n <= 0x7f then
+    return string.char(n)
+  elseif n <= 0x7ff then
+    return string.char(f(n / 64) + 192, n % 64 + 128)
+  elseif n <= 0xffff then
+    return string.char(f(n / 4096) + 224, f(n % 4096 / 64) + 128, n % 64 + 128)
+  elseif n <= 0x10ffff then
+    return string.char(f(n / 262144) + 240, f(n % 262144 / 4096) + 128,
+                       f(n % 4096 / 64) + 128, n % 64 + 128)
+  end
+  error( string.format("invalid unicode codepoint '%x'", n) )
+end
+
+
+local function parse_unicode_escape(s)
+  local n1 = tonumber( s:sub(1, 4),  16 )
+  local n2 = tonumber( s:sub(7, 10), 16 )
+   -- Surrogate pair?
+  if n2 then
+    return codepoint_to_utf8((n1 - 0xd800) * 0x400 + (n2 - 0xdc00) + 0x10000)
+  else
+    return codepoint_to_utf8(n1)
+  end
+end
+
+
+local function parse_string(str, i)
+  local res = ""
+  local j = i + 1
+  local k = j
+
+  while j <= #str do
+    local x = str:byte(j)
+
+    if x < 32 then
+      decode_error(str, j, "control character in string")
+
+    elseif x == 92 then -- `\`: Escape
+      res = res .. str:sub(k, j - 1)
+      j = j + 1
+      local c = str:sub(j, j)
+      if c == "u" then
+        local hex = str:match("^[dD][89aAbB]%x%x\\u%x%x%x%x", j + 1)
+                 or str:match("^%x%x%x%x", j + 1)
+                 or decode_error(str, j - 1, "invalid unicode escape in string")
+        res = res .. parse_unicode_escape(hex)
+        j = j + #hex
+      else
+        if not escape_chars[c] then
+          decode_error(str, j - 1, "invalid escape char '" .. c .. "' in string")
+        end
+        res = res .. escape_char_map_inv[c]
+      end
+      k = j + 1
+
+    elseif x == 34 then -- `"`: End of string
+      res = res .. str:sub(k, j - 1)
+      return res, j + 1
+    end
+
+    j = j + 1
+  end
+
+  decode_error(str, i, "expected closing quote for string")
+end
+
+
+local function parse_number(str, i)
+  local x = next_char(str, i, delim_chars)
+  local s = str:sub(i, x - 1)
+  local n = tonumber(s)
+  if not n then
+    decode_error(str, i, "invalid number '" .. s .. "'")
+  end
+  return n, x
+end
+
+
+local function parse_literal(str, i)
+  local x = next_char(str, i, delim_chars)
+  local word = str:sub(i, x - 1)
+  if not literals[word] then
+    decode_error(str, i, "invalid literal '" .. word .. "'")
+  end
+  return literal_map[word], x
+end
+
+
+local function parse_array(str, i)
+  local res = {}
+  local n = 1
+  i = i + 1
+  while 1 do
+    local x
+    i = next_char(str, i, space_chars, true)
+    -- Empty / end of array?
+    if str:sub(i, i) == "]" then
+      i = i + 1
+      break
+    end
+    -- Read token
+    x, i = parse(str, i)
+    res[n] = x
+    n = n + 1
+    -- Next token
+    i = next_char(str, i, space_chars, true)
+    local chr = str:sub(i, i)
+    i = i + 1
+    if chr == "]" then break end
+    if chr ~= "," then decode_error(str, i, "expected ']' or ','") end
+  end
+  return res, i
+end
+
+
+local function parse_object(str, i)
+  local res = {}
+  i = i + 1
+  while 1 do
+    local key, val
+    i = next_char(str, i, space_chars, true)
+    -- Empty / end of object?
+    if str:sub(i, i) == "}" then
+      i = i + 1
+      break
+    end
+    -- Read key
+    if str:sub(i, i) ~= '"' then
+      decode_error(str, i, "expected string for key")
+    end
+    key, i = parse(str, i)
+    -- Read ':' delimiter
+    i = next_char(str, i, space_chars, true)
+    if str:sub(i, i) ~= ":" then
+      decode_error(str, i, "expected ':' after key")
+    end
+    i = next_char(str, i + 1, space_chars, true)
+    -- Read value
+    val, i = parse(str, i)
+    -- Set
+    res[key] = val
+    -- Next token
+    i = next_char(str, i, space_chars, true)
+    local chr = str:sub(i, i)
+    i = i + 1
+    if chr == "}" then break end
+    if chr ~= "," then decode_error(str, i, "expected '}' or ','") end
+  end
+  return res, i
+end
+
+
+local char_func_map = {
+  [ '"' ] = parse_string,
+  [ "0" ] = parse_number,
+  [ "1" ] = parse_number,
+  [ "2" ] = parse_number,
+  [ "3" ] = parse_number,
+  [ "4" ] = parse_number,
+  [ "5" ] = parse_number,
+  [ "6" ] = parse_number,
+  [ "7" ] = parse_number,
+  [ "8" ] = parse_number,
+  [ "9" ] = parse_number,
+  [ "-" ] = parse_number,
+  [ "t" ] = parse_literal,
+  [ "f" ] = parse_literal,
+  [ "n" ] = parse_literal,
+  [ "[" ] = parse_array,
+  [ "{" ] = parse_object,
+}
+
+
+parse = function(str, idx)
+  local chr = str:sub(idx, idx)
+  local f = char_func_map[chr]
+  if f then
+    return f(str, idx)
+  end
+  decode_error(str, idx, "unexpected character '" .. chr .. "'")
+end
+
+
+function json.decode(str)
+  if type(str) ~= "string" then
+    error("expected argument of type string, got " .. type(str))
+  end
+  local res, idx = parse(str, next_char(str, 1, space_chars, true))
+  idx = next_char(str, idx, space_chars, true)
+  if idx <= #str then
+    decode_error(str, idx, "trailing garbage")
+  end
+  return res
+end
+
+return json

src/lib/tiny-ecs.lua

@@ -0,0 +1,864 @@
+--[[
+Copyright (c) 2016 Calvin Rose
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software is furnished to do so,
+subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+]]
+
+--- @module tiny-ecs
+-- @author Calvin Rose
+-- @license MIT
+-- @copyright 2016
+local tiny = {}
+
+-- Local versions of standard lua functions
+local tinsert = table.insert
+local tremove = table.remove
+local tsort = table.sort
+local setmetatable = setmetatable
+local type = type
+local select = select
+
+-- Local versions of the library functions
+local tiny_manageEntities
+local tiny_manageSystems
+local tiny_addEntity
+local tiny_addSystem
+local tiny_add
+local tiny_removeEntity
+local tiny_removeSystem
+
+--- Filter functions.
+-- A Filter is a function that selects which Entities apply to a System.
+-- Filters take two parameters, the System and the Entity, and return a boolean
+-- value indicating if the Entity should be processed by the System. A truthy
+-- value includes the entity, while a falsey (nil or false) value excludes the
+-- entity.
+--
+-- Filters must be added to Systems by setting the `filter` field of the System.
+-- Filter's returned by tiny-ecs's Filter functions are immutable and can be
+-- used by multiple Systems.
+--
+--    local f1 = tiny.requireAll("position", "velocity", "size")
+--    local f2 = tiny.requireAny("position", "velocity", "size")
+--
+--    local e1 = {
+--        position = {2, 3},
+--        velocity = {3, 3},
+--        size = {4, 4}
+--    }
+--
+--    local entity2 = {
+--        position = {4, 5},
+--        size = {4, 4}
+--    }
+--
+--    local e3 = {
+--        position = {2, 3},
+--        velocity = {3, 3}
+--    }
+--
+--    print(f1(nil, e1), f1(nil, e2), f1(nil, e3)) -- prints true, false, false
+--    print(f2(nil, e1), f2(nil, e2), f2(nil, e3)) -- prints true, true, true
+--
+-- Filters can also be passed as arguments to other Filter constructors. This is
+-- a powerful way to create complex, custom Filters that select a very specific
+-- set of Entities.
+--
+--    -- Selects Entities with an "image" Component, but not Entities with a
+--    -- "Player" or "Enemy" Component.
+--    filter = tiny.requireAll("image", tiny.rejectAny("Player", "Enemy"))
+--
+-- @section Filter
+
+-- A helper function to compile filters.
+local filterJoin
+
+-- A helper function to filters from string
+local filterBuildString
+
+do
+
+    local loadstring = loadstring or load
+    local function getchr(c)
+        return "\\" .. c:byte()
+    end
+    local function make_safe(text)
+        return ("%q"):format(text):gsub('\n', 'n'):gsub("[\128-\255]", getchr)
+    end
+
+    local function filterJoinRaw(prefix, seperator, ...)
+        local accum = {}
+        local build = {}
+        for i = 1, select('#', ...) do
+            local item = select(i, ...)
+            if type(item) == 'string' then
+                accum[#accum + 1] = ("(e[%s] ~= nil)"):format(make_safe(item))
+            elseif type(item) == 'function' then
+                build[#build + 1] = ('local subfilter_%d_ = select(%d, ...)')
+                    :format(i, i)
+                accum[#accum + 1] = ('(subfilter_%d_(system, e))'):format(i)
+            else
+                error 'Filter token must be a string or a filter function.'
+            end
+        end
+        local source = ('%s\nreturn function(system, e) return %s(%s) end')
+            :format(
+                table.concat(build, '\n'),
+                prefix,
+                table.concat(accum, seperator))
+        local loader, err = loadstring(source)
+        if err then error(err) end
+        return loader(...)
+    end
+
+    function filterJoin(...)
+        local state, value = pcall(filterJoinRaw, ...)
+        if state then return value else return nil, value end
+    end
+
+    local function buildPart(str)
+        local accum = {}
+        local subParts = {}
+        str = str:gsub('%b()', function(p)
+            subParts[#subParts + 1] = buildPart(p:sub(2, -2))
+            return ('\255%d'):format(#subParts)
+        end)
+        for invert, part, sep in str:gmatch('(%!?)([^%|%&%!]+)([%|%&]?)') do
+            if part:match('^\255%d+$') then
+                local partIndex = tonumber(part:match(part:sub(2)))
+                accum[#accum + 1] = ('%s(%s)')
+                    :format(invert == '' and '' or 'not', subParts[partIndex])
+            else
+                accum[#accum + 1] = ("(e[%s] %s nil)")
+                    :format(make_safe(part), invert == '' and '~=' or '==')
+            end
+            if sep ~= '' then
+                accum[#accum + 1] = (sep == '|' and ' or ' or ' and ')
+            end
+        end
+        return table.concat(accum)
+    end
+
+    function filterBuildString(str)
+        local source = ("return function(_, e) return %s end")
+            :format(buildPart(str))
+        local loader, err = loadstring(source)
+        if err then
+            error(err)
+        end
+        return loader()
+    end
+
+end
+
+--- Makes a Filter that selects Entities with all specified Components and
+-- Filters.
+function tiny.requireAll(...)
+    return filterJoin('', ' and ', ...)
+end
+
+--- Makes a Filter that selects Entities with at least one of the specified
+-- Components and Filters.
+function tiny.requireAny(...)
+    return filterJoin('', ' or ', ...)
+end
+
+--- Makes a Filter that rejects Entities with all specified Components and
+-- Filters, and selects all other Entities.
+function tiny.rejectAll(...)
+    return filterJoin('not', ' and ', ...)
+end
+
+--- Makes a Filter that rejects Entities with at least one of the specified
+-- Components and Filters, and selects all other Entities.
+function tiny.rejectAny(...)
+    return filterJoin('not', ' or ', ...)
+end
+
+--- Makes a Filter from a string. Syntax of `pattern` is as follows.
+--
+--   * Tokens are alphanumeric strings including underscores.
+--   * Tokens can be separated by |, &, or surrounded by parentheses.
+--   * Tokens can be prefixed with !, and are then inverted.
+--
+-- Examples are best:
+--    'a|b|c' - Matches entities with an 'a' OR 'b' OR 'c'.
+--    'a&!b&c' - Matches entities with an 'a' AND NOT 'b' AND 'c'.
+--    'a|(b&c&d)|e - Matches 'a' OR ('b' AND 'c' AND 'd') OR 'e'
+-- @param pattern
+function tiny.filter(pattern)
+    local state, value = pcall(filterBuildString, pattern)
+    if state then return value else return nil, value end
+end
+
+--- System functions.
+-- A System is a wrapper around function callbacks for manipulating Entities.
+-- Systems are implemented as tables that contain at least one method;
+-- an update function that takes parameters like so:
+--
+--   * `function system:update(dt)`.
+--
+-- There are also a few other optional callbacks:
+--
+--   * `function system:filter(entity)` - Returns true if this System should
+-- include this Entity, otherwise should return false. If this isn't specified,
+-- no Entities are included in the System.
+--   * `function system:onAdd(entity)` - Called when an Entity is added to the
+-- System.
+--   * `function system:onRemove(entity)` - Called when an Entity is removed
+-- from the System.
+--   * `function system:onModify(dt)` - Called when the System is modified by
+-- adding or removing Entities from the System.
+--   * `function system:onAddToWorld(world)` - Called when the System is added
+-- to the World, before any entities are added to the system.
+--   * `function system:onRemoveFromWorld(world)` - Called when the System is
+-- removed from the world, after all Entities are removed from the System.
+--   * `function system:preWrap(dt)` - Called on each system before update is
+-- called on any system.
+--   * `function system:postWrap(dt)` - Called on each system in reverse order
+-- after update is called on each system. The idea behind `preWrap` and
+-- `postWrap` is to allow for systems that modify the behavior of other systems.
+-- Say there is a DrawingSystem, which draws sprites to the screen, and a
+-- PostProcessingSystem, that adds some blur and bloom effects. In the preWrap
+-- method of the PostProcessingSystem, the System could set the drawing target
+-- for the DrawingSystem to a special buffer instead the screen. In the postWrap
+-- method, the PostProcessingSystem could then modify the buffer and render it
+-- to the screen. In this setup, the PostProcessingSystem would be added to the
+-- World after the drawingSystem (A similar but less flexible behavior could
+-- be accomplished with a single custom update function in the DrawingSystem).
+--
+-- For Filters, it is convenient to use `tiny.requireAll` or `tiny.requireAny`,
+-- but one can write their own filters as well. Set the Filter of a System like
+-- so:
+--    system.filter = tiny.requireAll("a", "b", "c")
+-- or
+--    function system:filter(entity)
+--        return entity.myRequiredComponentName ~= nil
+--    end
+--
+-- All Systems also have a few important fields that are initialized when the
+-- system is added to the World. A few are important, and few should be less
+-- commonly used.
+--
+--   * The `world` field points to the World that the System belongs to. Useful
+-- for adding and removing Entities from the world dynamically via the System.
+--   * The `active` flag is whether or not the System is updated automatically.
+-- Inactive Systems should be updated manually or not at all via
+-- `system:update(dt)`. Defaults to true.
+--   * The `entities` field is an ordered list of Entities in the System. This
+-- list can be used to quickly iterate through all Entities in a System.
+--   * The `interval` field is an optional field that makes Systems update at
+-- certain intervals using buffered time, regardless of World update frequency.
+-- For example, to make a System update once a second, set the System's interval
+-- to 1.
+--   * The `index` field is the System's index in the World. Lower indexed
+-- Systems are processed before higher indices. The `index` is a read only
+-- field; to set the `index`, use `tiny.setSystemIndex(world, system)`.
+--   * The `indices` field is a table of Entity keys to their indices in the
+-- `entities` list. Most Systems can ignore this.
+--   * The `modified` flag is an indicator if the System has been modified in
+-- the last update. If so, the `onModify` callback will be called on the System
+-- in the next update, if it has one. This is usually managed by tiny-ecs, so
+-- users should mostly ignore this, too.
+--
+-- There is another option to (hopefully) increase performance in systems that
+-- have items added to or removed from them often, and have lots of entities in
+-- them.  Setting the `nocache` field of the system might improve performance.
+-- It is still experimental. There are some restriction to systems without
+-- caching, however.
+--
+--   * There is no `entities` table.
+--   * Callbacks such onAdd, onRemove, and onModify will never be called
+--   * Noncached systems cannot be sorted (There is no entities list to sort).
+--
+-- @section System
+
+-- Use an empty table as a key for identifying Systems. Any table that contains
+-- this key is considered a System rather than an Entity.
+local systemTableKey = { "SYSTEM_TABLE_KEY" }
+
+-- Checks if a table is a System.
+local function isSystem(table)
+    return table[systemTableKey]
+end
+
+-- Update function for all Processing Systems.
+local function processingSystemUpdate(system, dt)
+    local preProcess = system.preProcess
+    local process = system.process
+    local postProcess = system.postProcess
+
+    if preProcess then
+        preProcess(system, dt)
+    end
+
+    if process then
+        if system.nocache then
+            local entities = system.world.entities
+            local filter = system.filter
+            if filter then
+                for i = 1, #entities do
+                    local entity = entities[i]
+                    if filter(system, entity) then
+                        process(system, entity, dt)
+                    end
+                end
+            end
+        else
+            local entities = system.entities
+            for i = 1, #entities do
+                process(system, entities[i], dt)
+            end
+        end
+    end
+
+    if postProcess then
+        postProcess(system, dt)
+    end
+end
+
+-- Sorts Systems by a function system.sortDelegate(entity1, entity2) on modify.
+local function sortedSystemOnModify(system)
+    local entities = system.entities
+    local indices = system.indices
+    local sortDelegate = system.sortDelegate
+    if not sortDelegate then
+        local compare = system.compare
+        sortDelegate = function(e1, e2)
+            return compare(system, e1, e2)
+        end
+        system.sortDelegate = sortDelegate
+    end
+    tsort(entities, sortDelegate)
+    for i = 1, #entities do
+        indices[entities[i]] = i
+    end
+end
+
+--- Creates a new System or System class from the supplied table. If `table` is
+-- nil, creates a new table.
+function tiny.system(table)
+    table = table or {}
+    table[systemTableKey] = true
+    return table
+end
+
+--- Creates a new Processing System or Processing System class. Processing
+-- Systems process each entity individual, and are usually what is needed.
+-- Processing Systems have three extra callbacks besides those inheritted from
+-- vanilla Systems.
+--
+--     function system:preProcess(dt) -- Called before iteration.
+--     function system:process(entity, dt) -- Process each entity.
+--     function system:postProcess(dt) -- Called after iteration.
+--
+-- Processing Systems have their own `update` method, so don't implement a
+-- a custom `update` callback for Processing Systems.
+-- @see system
+function tiny.processingSystem(table)
+    table = table or {}
+    table[systemTableKey] = true
+    table.update = processingSystemUpdate
+    return table
+end
+
+--- Creates a new Sorted System or Sorted System class. Sorted Systems sort
+-- their Entities according to a user-defined method, `system:compare(e1, e2)`,
+-- which should return true if `e1` should come before `e2` and false otherwise.
+-- Sorted Systems also override the default System's `onModify` callback, so be
+-- careful if defining a custom callback. However, for processing the sorted
+-- entities, consider `tiny.sortedProcessingSystem(table)`.
+-- @see system
+function tiny.sortedSystem(table)
+    table = table or {}
+    table[systemTableKey] = true
+    table.onModify = sortedSystemOnModify
+    return table
+end
+
+--- Creates a new Sorted Processing System or Sorted Processing System class.
+-- Sorted Processing Systems have both the aspects of Processing Systems and
+-- Sorted Systems.
+-- @see system
+-- @see processingSystem
+-- @see sortedSystem
+function tiny.sortedProcessingSystem(table)
+    table = table or {}
+    table[systemTableKey] = true
+    table.update = processingSystemUpdate
+    table.onModify = sortedSystemOnModify
+    return table
+end
+
+--- World functions.
+-- A World is a container that manages Entities and Systems. Typically, a
+-- program uses one World at a time.
+--
+-- For all World functions except `tiny.world(...)`, object-oriented syntax can
+-- be used instead of the documented syntax. For example,
+-- `tiny.add(world, e1, e2, e3)` is the same as `world:add(e1, e2, e3)`.
+-- @section World
+
+-- Forward declaration
+local worldMetaTable
+
+--- Creates a new World.
+-- Can optionally add default Systems and Entities. Returns the new World along
+-- with default Entities and Systems.
+function tiny.world(...)
+    local ret = setmetatable({
+
+        -- List of Entities to remove
+        entitiesToRemove = {},
+
+        -- List of Entities to change
+        entitiesToChange = {},
+
+        -- List of Entities to add
+        systemsToAdd = {},
+
+        -- List of Entities to remove
+        systemsToRemove = {},
+
+        -- Set of Entities
+        entities = {},
+
+        -- List of Systems
+        systems = {}
+
+    }, worldMetaTable)
+
+    tiny_add(ret, ...)
+    tiny_manageSystems(ret)
+    tiny_manageEntities(ret)
+
+    return ret, ...
+end
+
+--- Adds an Entity to the world.
+-- Also call this on Entities that have changed Components such that they
+-- match different Filters. Returns the Entity.
+function tiny.addEntity(world, entity)
+    local e2c = world.entitiesToChange
+    e2c[#e2c + 1] = entity
+    return entity
+end
+tiny_addEntity = tiny.addEntity
+
+--- Adds a System to the world. Returns the System.
+function tiny.addSystem(world, system)
+    assert(system.world == nil, "System already belongs to a World.")
+    local s2a = world.systemsToAdd
+    s2a[#s2a + 1] = system
+    system.world = world
+    return system
+end
+tiny_addSystem = tiny.addSystem
+
+--- Shortcut for adding multiple Entities and Systems to the World. Returns all
+-- added Entities and Systems.
+function tiny.add(world, ...)
+    for i = 1, select("#", ...) do
+        local obj = select(i, ...)
+        if obj then
+            if isSystem(obj) then
+                tiny_addSystem(world, obj)
+            else -- Assume obj is an Entity
+                tiny_addEntity(world, obj)
+            end
+        end
+    end
+    return ...
+end
+tiny_add = tiny.add
+
+--- Removes an Entity from the World. Returns the Entity.
+function tiny.removeEntity(world, entity)
+    local e2r = world.entitiesToRemove
+    e2r[#e2r + 1] = entity
+    return entity
+end
+tiny_removeEntity = tiny.removeEntity
+
+--- Removes a System from the world. Returns the System.
+function tiny.removeSystem(world, system)
+    assert(system.world == world, "System does not belong to this World.")
+    local s2r = world.systemsToRemove
+    s2r[#s2r + 1] = system
+    return system
+end
+tiny_removeSystem = tiny.removeSystem
+
+--- Shortcut for removing multiple Entities and Systems from the World. Returns
+-- all removed Systems and Entities
+function tiny.remove(world, ...)
+    for i = 1, select("#", ...) do
+        local obj = select(i, ...)
+        if obj then
+            if isSystem(obj) then
+                tiny_removeSystem(world, obj)
+            else -- Assume obj is an Entity
+                tiny_removeEntity(world, obj)
+            end
+        end
+    end
+    return ...
+end
+
+-- Adds and removes Systems that have been marked from the World.
+function tiny_manageSystems(world)
+    local s2a, s2r = world.systemsToAdd, world.systemsToRemove
+
+    -- Early exit
+    if #s2a == 0 and #s2r == 0 then
+        return
+    end
+
+    world.systemsToAdd = {}
+    world.systemsToRemove = {}
+
+    local worldEntityList = world.entities
+    local systems = world.systems
+
+    -- Remove Systems
+    for i = 1, #s2r do
+        local system = s2r[i]
+        local index = system.index
+        local onRemove = system.onRemove
+        if onRemove and not system.nocache then
+            local entityList = system.entities
+            for j = 1, #entityList do
+                onRemove(system, entityList[j])
+            end
+        end
+        tremove(systems, index)
+        for j = index, #systems do
+            systems[j].index = j
+        end
+        local onRemoveFromWorld = system.onRemoveFromWorld
+        if onRemoveFromWorld then
+            onRemoveFromWorld(system, world)
+        end
+        s2r[i] = nil
+
+        -- Clean up System
+        system.world = nil
+        system.entities = nil
+        system.indices = nil
+        system.index = nil
+    end
+
+    -- Add Systems
+    for i = 1, #s2a do
+        local system = s2a[i]
+        if systems[system.index or 0] ~= system then
+            if not system.nocache then
+                system.entities = {}
+                system.indices = {}
+            end
+            if system.active == nil then
+                system.active = true
+            end
+            system.modified = true
+            system.world = world
+            local index = #systems + 1
+            system.index = index
+            systems[index] = system
+            local onAddToWorld = system.onAddToWorld
+            if onAddToWorld then
+                onAddToWorld(system, world)
+            end
+
+            -- Try to add Entities
+            if not system.nocache then
+                local entityList = system.entities
+                local entityIndices = system.indices
+                local onAdd = system.onAdd
+                local filter = system.filter
+                if filter then
+                    for j = 1, #worldEntityList do
+                        local entity = worldEntityList[j]
+                        if filter(system, entity) then
+                            local entityIndex = #entityList + 1
+                            entityList[entityIndex] = entity
+                            entityIndices[entity] = entityIndex
+                            if onAdd then
+                                onAdd(system, entity)
+                            end
+                        end
+                    end
+                end
+            end
+        end
+        s2a[i] = nil
+    end
+end
+
+-- Adds, removes, and changes Entities that have been marked.
+function tiny_manageEntities(world)
+
+    local e2r = world.entitiesToRemove
+    local e2c = world.entitiesToChange
+
+    -- Early exit
+    if #e2r == 0 and #e2c == 0 then
+        return
+    end
+
+    world.entitiesToChange = {}
+    world.entitiesToRemove = {}
+
+    local entities = world.entities
+    local systems = world.systems
+
+    -- Change Entities
+    for i = 1, #e2c do
+        local entity = e2c[i]
+        -- Add if needed
+        if not entities[entity] then
+            local index = #entities + 1
+            entities[entity] = index
+            entities[index] = entity
+        end
+        for j = 1, #systems do
+            local system = systems[j]
+            if not system.nocache then
+                local ses = system.entities
+                local seis = system.indices
+                local index = seis[entity]
+                local filter = system.filter
+                if filter and filter(system, entity) then
+                    if not index then
+                        system.modified = true
+                        index = #ses + 1
+                        ses[index] = entity
+                        seis[entity] = index
+                        local onAdd = system.onAdd
+                        if onAdd then
+                            onAdd(system, entity)
+                        end
+                    end
+                elseif index then
+                    system.modified = true
+                    local tmpEntity = ses[#ses]
+                    ses[index] = tmpEntity
+                    seis[tmpEntity] = index
+                    seis[entity] = nil
+                    ses[#ses] = nil
+                    local onRemove = system.onRemove
+                    if onRemove then
+                        onRemove(system, entity)
+                    end
+                end
+            end
+        end
+        e2c[i] = nil
+    end
+
+    -- Remove Entities
+    for i = 1, #e2r do
+        local entity = e2r[i]
+        e2r[i] = nil
+        local listIndex = entities[entity]
+        if listIndex then
+            -- Remove Entity from world state
+            local lastEntity = entities[#entities]
+            entities[lastEntity] = listIndex
+            entities[entity] = nil
+            entities[listIndex] = lastEntity
+            entities[#entities] = nil
+            -- Remove from cached systems
+            for j = 1, #systems do
+                local system = systems[j]
+                if not system.nocache then
+                    local ses = system.entities
+                    local seis = system.indices
+                    local index = seis[entity]
+                    if index then
+                        system.modified = true
+                        local tmpEntity = ses[#ses]
+                        ses[index] = tmpEntity
+                        seis[tmpEntity] = index
+                        seis[entity] = nil
+                        ses[#ses] = nil
+                        local onRemove = system.onRemove
+                        if onRemove then
+                            onRemove(system, entity)
+                        end
+                    end
+                end
+            end
+        end
+    end
+end
+
+--- Manages Entities and Systems marked for deletion or addition. Call this
+-- before modifying Systems and Entities outside of a call to `tiny.update`.
+-- Do not call this within a call to `tiny.update`.
+function tiny.refresh(world)
+    tiny_manageSystems(world)
+    tiny_manageEntities(world)
+    local systems = world.systems
+    for i = #systems, 1, -1 do
+        local system = systems[i]
+        if system.active then
+            local onModify = system.onModify
+            if onModify and system.modified then
+                onModify(system, 0)
+            end
+            system.modified = false
+        end
+    end
+end
+
+--- Updates the World by dt (delta time). Takes an optional parameter, `filter`,
+-- which is a Filter that selects Systems from the World, and updates only those
+-- Systems. If `filter` is not supplied, all Systems are updated. Put this
+-- function in your main loop.
+function tiny.update(world, dt, filter)
+
+    tiny_manageSystems(world)
+    tiny_manageEntities(world)
+
+    local systems = world.systems
+
+    -- Iterate through Systems IN REVERSE ORDER
+    for i = #systems, 1, -1 do
+        local system = systems[i]
+        if system.active then
+            -- Call the modify callback on Systems that have been modified.
+            local onModify = system.onModify
+            if onModify and system.modified then
+                onModify(system, dt)
+            end
+            local preWrap = system.preWrap
+            if preWrap and
+                ((not filter) or filter(world, system)) then
+                preWrap(system, dt)
+            end
+        end
+    end
+
+    --  Iterate through Systems IN ORDER
+    for i = 1, #systems do
+        local system = systems[i]
+        if system.active and ((not filter) or filter(world, system)) then
+
+            -- Update Systems that have an update method (most Systems)
+            local update = system.update
+            if update then
+                local interval = system.interval
+                if interval then
+                    local bufferedTime = (system.bufferedTime or 0) + dt
+                    while bufferedTime >= interval do
+                        bufferedTime = bufferedTime - interval
+                        update(system, interval)
+                    end
+                    system.bufferedTime = bufferedTime
+                else
+                    update(system, dt)
+                end
+            end
+
+            system.modified = false
+        end
+    end
+
+    -- Iterate through Systems IN ORDER AGAIN
+    for i = 1, #systems do
+        local system = systems[i]
+        local postWrap = system.postWrap
+        if postWrap and system.active and
+            ((not filter) or filter(world, system)) then
+            postWrap(system, dt)
+        end
+    end
+
+end
+
+--- Removes all Entities from the World.
+function tiny.clearEntities(world)
+    local el = world.entities
+    for i = 1, #el do
+        tiny_removeEntity(world, el[i])
+    end
+end
+
+--- Removes all Systems from the World.
+function tiny.clearSystems(world)
+    local systems = world.systems
+    for i = #systems, 1, -1 do
+        tiny_removeSystem(world, systems[i])
+    end
+end
+
+--- Gets number of Entities in the World.
+function tiny.getEntityCount(world)
+    return #world.entities
+end
+
+--- Gets number of Systems in World.
+function tiny.getSystemCount(world)
+    return #world.systems
+end
+
+--- Sets the index of a System in the World, and returns the old index. Changes
+-- the order in which they Systems processed, because lower indexed Systems are
+-- processed first. Returns the old system.index.
+function tiny.setSystemIndex(world, system, index)
+    tiny_manageSystems(world)
+    local oldIndex = system.index
+    local systems = world.systems
+
+    if index < 0 then
+        index = tiny.getSystemCount(world) + 1 + index
+    end
+
+    tremove(systems, oldIndex)
+    tinsert(systems, index, system)
+
+    for i = oldIndex, index, index >= oldIndex and 1 or -1 do
+        systems[i].index = i
+    end
+
+    return oldIndex
+end
+
+-- Construct world metatable.
+worldMetaTable = {
+    __index = {
+        add = tiny.add,
+        addEntity = tiny.addEntity,
+        addSystem = tiny.addSystem,
+        remove = tiny.remove,
+        removeEntity = tiny.removeEntity,
+        removeSystem = tiny.removeSystem,
+        refresh = tiny.refresh,
+        update = tiny.update,
+        clearEntities = tiny.clearEntities,
+        clearSystems = tiny.clearSystems,
+        getEntityCount = tiny.getEntityCount,
+        getSystemCount = tiny.getSystemCount,
+        setSystemIndex = tiny.setSystemIndex
+    },
+    __tostring = function()
+        return "<tiny-ecs_World>"
+    end
+}
+
+return tiny

src/lovr/.gitignore

@@ -0,0 +1 @@
+.DS_Store

src/lovr/LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2026 Donald Hays
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

src/lovr/README.md

@@ -0,0 +1,4 @@
+# IUI-SAMPLE-LÖVR
+
+A sample project for the [IUI](https://github.com/DonaldHays/iui) immediate mode
+GUI library using the [LÖVR](https://lovr.org/) game framework.

src/lovr/conf.lua

@@ -0,0 +1,24 @@
+local util = require("util")
+local launch = require "launch"
+
+local function isVR()
+    return launch.mode == "vr" or util.match(arg,"--desktop") == false
+end
+
+local function isResizable()
+    return launch.mode == "desktop" 
+end
+
+function lovr.conf(t)
+    if isVR() then
+        t.headset.supersample = 2
+    else
+        t.modules.headset = nil
+    end
+
+    t.identity     = "xurfer"
+    t.window.title = "X U R F Ξ R"
+    t.window.width = 1280
+    t.window.height = 720
+    t.window.resizable = isResizable()
+end

src/lovr/launch.lua

@@ -0,0 +1,23 @@
+local system = require "lovr.system"
+
+--- A type that customizes how the app launches.
+---
+--- Currently, the only launch option is the `mode`, which may be either
+--- "desktop" or "vr". On PC, you can change the option in the table literal
+--- below to change which mode the app launches in.
+---
+--- @class LaunchOptions
+--- @field mode IUIIdiom
+
+--- @type LaunchOptions
+local launchOptions = {
+    mode = "desktop",
+}
+
+--- If we're on Android, then we're on a mobile VR headset, so force the mode to
+--- "vr", regardless of the prior setting.
+if system.getOS() == "Android" then
+    launchOptions.mode = "vr"
+end
+
+return launchOptions

src/lovr/lib/iui/.gitignore

@@ -0,0 +1,2 @@
+.DS_Store
+.vscode

src/lovr/lib/iui/LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2026 Donald Hays
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

src/lovr/lib/iui/README.md

@@ -0,0 +1,20 @@
+# IUI
+
+An immediate mode GUI library for LUA projects.
+
+[Documentation](https://donaldhays.com/iui-docs/)
+
+## Installation
+
+This library must be paired with a backend that connects it to your game engine
+of choice. Some available backends:
+
+- [love-iui](https://github.com/DonaldHays/love-iui): LÖVE
+- [lovr-iui](https://github.com/DonaldHays/lovr-iui): LÖVR
+
+## Samples
+
+Sample projects are available that show the library in use.
+
+- [iui-sample-love](https://github.com/DonaldHays/iui-sample-love): LÖVE
+- [iui-sample-lovr](https://github.com/DonaldHays/iui-sample-lovr): LÖVR

src/lovr/lib/iui/color.lua

@@ -0,0 +1,45 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+
+--- @class IUILib
+local iui = require(currentPath .. "iui")
+
+--- @class IUIColor
+--- @field r number
+--- @field g number
+--- @field b number
+--- @field a number
+local color = {}
+color.__index = color
+
+function color:set()
+    iui.graphics.setColor(self.r, self.g, self.b, self.a)
+end
+
+--- @param r number
+--- @param g number
+--- @param b number
+--- @param a? number
+--- @return IUIColor
+function iui.newColor(r, g, b, a)
+    return setmetatable({ r = r, g = g, b = b, a = a or 1 }, color)
+end
+
+iui.colors = {
+    sysAccent500 = iui.newColor(14 / 255, 59 / 255, 173 / 255),
+
+    sysGray0 = iui.newColor(0.014, 0.014, 0.016),
+    sysGray50 = iui.newColor(0.083, 0.083, 0.097),
+    sysGray100 = iui.newColor(0.13, 0.13, 0.15),
+    sysGray200 = iui.newColor(0.28, 0.28, 0.32),
+    sysGray300 = iui.newColor(0.403, 0.403, 0.457),
+    sysGray400 = iui.newColor(0.47, 0.47, 0.53),
+    sysGray500 = iui.newColor(0.543, 0.543, 0.597),
+    sysGray600 = iui.newColor(0.628, 0.628, 0.672),
+    sysGray700 = iui.newColor(0.723, 0.723, 0.757),
+    sysGray800 = iui.newColor(0.818, 0.818, 0.842),
+    sysGray900 = iui.newColor(0.914, 0.914, 0.926),
+    sysGray950 = iui.newColor(0.957, 0.957, 0.963),
+    sysGray1000 = iui.newColor(0.989, 0.989, 0.991),
+
+    white = iui.newColor(1, 1, 1)
+}

src/lovr/lib/iui/draw-queue.lua

@@ -0,0 +1,265 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+
+--- @class IUILib
+local iui = require(currentPath .. "iui")
+
+local backend --- @type IUIGraphicsBackend
+
+--- @class IUIDrawQueue: IUIGraphicsBackend
+local drawQueue = {}
+
+--- @class (exact) IUIClipDrawCommand: IUIDrawCommand
+--- @field x? number
+--- @field y? number
+--- @field w? number
+--- @field h? number
+
+--- @param cmd IUIClipDrawCommand
+local function commitClip(cmd)
+    backend.clip(cmd.x, cmd.y, cmd.w, cmd.h)
+end
+
+function drawQueue.clip(x, y, w, h)
+    --- @type IUIClipDrawCommand
+    local cmd = iui.pool.get("clip_draw_command")
+
+    cmd.x = x
+    cmd.y = y
+    cmd.w = w
+    cmd.h = h
+    cmd.commit = commitClip
+
+    iui.draw.enqueue(cmd)
+end
+
+--- @class (exact) IUISetColorDrawCommand: IUIDrawCommand
+--- @field r number
+--- @field g number
+--- @field b number
+--- @field a? number
+
+--- @param cmd IUISetColorDrawCommand
+local function commitSetColor(cmd)
+    backend.setColor(cmd.r, cmd.g, cmd.b, cmd.a)
+end
+
+function drawQueue.setColor(r, g, b, a)
+    --- @type IUISetColorDrawCommand
+    local cmd = iui.pool.get("set_color_draw_command")
+
+    cmd.r = r
+    cmd.g = g
+    cmd.b = b
+    cmd.a = a
+    cmd.commit = commitSetColor
+
+    iui.draw.enqueue(cmd)
+end
+
+--- @class (exact) IUIRectangleDrawCommand: IUIDrawCommand
+--- @field x number
+--- @field y number
+--- @field w number
+--- @field h number
+--- @field rx? number
+--- @field ry? number
+
+--- @param cmd IUIRectangleDrawCommand
+local function commitRectangle(cmd)
+    backend.rectangle(cmd.x, cmd.y, cmd.w, cmd.h, cmd.rx, cmd.ry)
+end
+
+function drawQueue.rectangle(x, y, w, h, rx, ry)
+    --- @type IUIRectangleDrawCommand
+    local cmd = iui.pool.get("rectangle_draw_command")
+
+    cmd.x = x
+    cmd.y = y
+    cmd.w = w
+    cmd.h = h
+    cmd.rx = rx
+    cmd.ry = ry
+    cmd.commit = commitRectangle
+
+    iui.draw.enqueue(cmd)
+end
+
+--- @class (exact) IUICircleDrawCommand: IUIDrawCommand
+--- @field x number
+--- @field y number
+--- @field r number
+
+--- @param cmd IUICircleDrawCommand
+local function commitCircle(cmd)
+    backend.circle(cmd.x, cmd.y, cmd.r)
+end
+
+function drawQueue.circle(x, y, r)
+    --- @type IUICircleDrawCommand
+    local cmd = iui.pool.get("circle_draw_command")
+
+    cmd.x = x
+    cmd.y = y
+    cmd.r = r
+    cmd.commit = commitCircle
+
+    iui.draw.enqueue(cmd)
+end
+
+--- @class (exact) IUISetFontDrawCommand: IUIDrawCommand
+--- @field f any
+
+--- @param cmd IUISetFontDrawCommand
+local function commitSetFont(cmd)
+    backend.setFont(cmd.f)
+end
+
+function drawQueue.setFont(f)
+    --- @type IUISetFontDrawCommand
+    local cmd = iui.pool.get("set_font_draw_command")
+
+    cmd.f = f
+    cmd.commit = commitSetFont
+
+    iui.draw.enqueue(cmd)
+end
+
+--- @class (exact) IUIPrintDrawCommand: IUIDrawCommand
+--- @field s string
+--- @field x number
+--- @field y number
+
+--- @param cmd IUIPrintDrawCommand
+local function commitPrint(cmd)
+    backend.print(cmd.s, cmd.x, cmd.y)
+end
+
+function drawQueue.print(s, x, y)
+    --- @type IUIPrintDrawCommand
+    local cmd = iui.pool.get("print_draw_command")
+
+    cmd.s = s
+    cmd.x = x
+    cmd.y = y
+    cmd.commit = commitPrint
+
+    iui.draw.enqueue(cmd)
+end
+
+--- @class (exact) IUIImageDrawCommand: IUIDrawCommand
+--- @field image any
+--- @field filter IUIImageFilter
+--- @field x number
+--- @field y number
+--- @field w number
+--- @field h number
+
+--- @param cmd IUIImageDrawCommand
+local function commitImage(cmd)
+    backend.image(cmd.image, cmd.filter, cmd.x, cmd.y, cmd.w, cmd.h)
+end
+
+function drawQueue.image(image, filter, x, y, w, h)
+    --- @type IUIImageDrawCommand
+    local cmd = iui.pool.get("image_draw_command")
+
+    cmd.image = image
+    cmd.filter = filter
+    cmd.x = x
+    cmd.y = y
+    cmd.w = w
+    cmd.h = h
+    cmd.commit = commitImage
+
+    iui.draw.enqueue(cmd)
+end
+
+--- @class (exact) IUIMSDFImageDrawCommand: IUIDrawCommand
+--- @field image any
+--- @field x number
+--- @field y number
+--- @field w number
+--- @field h number
+
+--- @param cmd IUIMSDFImageDrawCommand
+local function commitMSDFImage(cmd)
+    backend.msdfImage(cmd.image, cmd.x, cmd.y, cmd.w, cmd.h)
+end
+
+function drawQueue.msdfImage(image, x, y, w, h)
+    --- @type IUIMSDFImageDrawCommand
+    local cmd = iui.pool.get("msdf_image_draw_command")
+
+    cmd.image = image
+    cmd.x = x
+    cmd.y = y
+    cmd.w = w
+    cmd.h = h
+    cmd.commit = commitMSDFImage
+
+    iui.draw.enqueue(cmd)
+end
+
+--- @class (exact) IUINineSliceDrawCommand: IUIDrawCommand
+--- @field nineSlice IUIImage9Slice
+--- @field filter IUIImageFilter
+--- @field x number
+--- @field y number
+--- @field w number
+--- @field h number
+
+--- @param cmd IUINineSliceDrawCommand
+local function commitNineSlice(cmd)
+    backend.nineSlice(cmd.nineSlice, cmd.filter, cmd.x, cmd.y, cmd.w, cmd.h)
+end
+
+function drawQueue.nineSlice(nineSlice, filter, x, y, w, h)
+    --- @type IUINineSliceDrawCommand
+    local cmd = iui.pool.get("nine_slice_draw_command")
+
+    cmd.nineSlice = nineSlice
+    cmd.filter = filter
+    cmd.x = x
+    cmd.y = y
+    cmd.w = w
+    cmd.h = h
+    cmd.commit = commitNineSlice
+
+    iui.draw.enqueue(cmd)
+end
+
+--- @class (exact) IUIMSDFNineSliceDrawCommand: IUIDrawCommand
+--- @field nineSlice IUIImage9Slice
+--- @field x number
+--- @field y number
+--- @field w number
+--- @field h number
+
+--- @param cmd IUIMSDFNineSliceDrawCommand
+local function commitMSDFNineSlice(cmd)
+    backend.msdfNineSlice(cmd.nineSlice, cmd.x, cmd.y, cmd.w, cmd.h)
+end
+
+function drawQueue.msdfNineSlice(nineSlice, x, y, w, h)
+    --- @type IUIMSDFNineSliceDrawCommand
+    local cmd = iui.pool.get("msdf_nine_slice_draw_command")
+
+    cmd.nineSlice = nineSlice
+    cmd.x = x
+    cmd.y = y
+    cmd.w = w
+    cmd.h = h
+    cmd.commit = commitMSDFNineSlice
+
+    iui.draw.enqueue(cmd)
+end
+
+--- @param graphicsBackend IUIGraphicsBackend
+function drawQueue.setBackend(graphicsBackend)
+    backend = graphicsBackend
+    setmetatable(drawQueue, {
+        __index = graphicsBackend
+    })
+end
+
+iui.drawQueue = drawQueue

src/lovr/lib/iui/draw.lua

@@ -0,0 +1,223 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+
+--- @class IUILib
+local iui = require(currentPath .. "iui")
+
+--- @class IUIDraw
+--- @overload fun()
+local draw = {}
+
+--- @class (exact) IUIDrawCommand
+--- @field commit fun(command: IUIDrawCommand)
+
+--- @class (exact) IUIDrawContext
+--- @field commands IUIDrawCommand[]
+--- @field currentClip? number[]
+--- @field clipStack number[][]
+--- @field hideCount number
+
+--- @class (exact) IUIDrawRootContext
+--- @field width number
+--- @field height number
+--- @field drawContexts IUIDrawContext[]
+--- @field contextIndex number
+
+local ctx --- @type IUIDrawRootContext
+
+--- @param idx? number
+--- @return IUIDrawContext
+local function getDrawContext(idx)
+    return ctx.drawContexts[idx or ctx.contextIndex]
+end
+
+setmetatable(draw --[[@as any]], {
+    __call = function(_, onDraw)
+        if onDraw then
+            error("IUI no longer takes draw blocks")
+        else
+            iui.graphics.beginDraw(ctx.width, ctx.height)
+            for _, context in ipairs(ctx.drawContexts) do
+                for _, command in ipairs(context.commands) do
+                    command.commit(command)
+                    iui.pool.put(command)
+                end
+            end
+            iui.graphics.endDraw()
+        end
+    end
+})
+
+--- @param command IUIDrawCommand
+--- @overload fun(f: function)
+function draw.enqueue(command)
+    local drawContext = getDrawContext()
+    if drawContext.hideCount == 0 then
+        if type(command) == "function" then
+            --- @type IUIDrawCommand
+            local cmd = iui.pool.get("function_draw_command")
+
+            cmd.commit = command
+
+            table.insert(drawContext.commands, cmd)
+        else
+            table.insert(drawContext.commands, command)
+        end
+    end
+end
+
+--- @return IUIDrawRootContext
+function draw.newRootContext()
+    --- @type IUIDrawRootContext
+    return {
+        width = 0,
+        height = 0,
+        drawContexts = {},
+        contextIndex = 0
+    }
+end
+
+--- @param windowManager IUIWindowManager
+function draw.setWindowManager(windowManager)
+    ctx = windowManager.draw
+end
+
+function draw.beginFrame()
+    ctx.drawContexts = {}
+end
+
+function draw.endFrame()
+    if getDrawContext().currentClip ~= nil then
+        error("Clip stack was not empty at end of frame")
+    end
+end
+
+function draw.setWindowSize(width, height)
+    ctx.width, ctx.height = width, height
+end
+
+function draw.beginContext()
+    --- @type IUIDrawContext
+    local drawContext = {
+        clipStack = {},
+        commands = {},
+        hideCount = 0
+    }
+    table.insert(ctx.drawContexts, drawContext)
+    ctx.contextIndex = #ctx.drawContexts
+end
+
+function draw.endContext()
+    if getDrawContext().hideCount ~= 0 then
+        error("Hide count was not 0 at end of context")
+    end
+
+    ctx.contextIndex = ctx.contextIndex - 1
+end
+
+function draw.beginHiding()
+    getDrawContext().hideCount = getDrawContext().hideCount + 1
+end
+
+function draw.endHiding()
+    getDrawContext().hideCount = getDrawContext().hideCount - 1
+end
+
+--- @param x number The x coordinate of the clip region
+--- @param y number The y coordinate of the clip region
+--- @param w number The width of the clip region
+--- @param h number The height of the clip region
+function draw.pushClip(x, y, w, h)
+    local drawContext = getDrawContext()
+    local currentClip = drawContext.currentClip
+    if currentClip then
+        table.insert(drawContext.clipStack, currentClip)
+
+        local maxX, maxY = x + w, y + h
+        local cx, cy = currentClip[1], currentClip[2]
+        local cMaxX, cMaxY = cx + currentClip[3], cy + currentClip[4]
+
+        x = math.max(x, cx)
+        y = math.max(y, cy)
+        maxX = math.min(maxX, cMaxX)
+        maxY = math.min(maxY, cMaxY)
+
+        w = math.max(0, maxX - x)
+        h = math.max(0, maxY - y)
+    end
+
+    drawContext.currentClip = { x, y, w, h }
+    iui.graphics.clip(x, y, w, h)
+end
+
+function draw.popClip()
+    local drawContext = getDrawContext()
+    if drawContext.currentClip == nil then
+        error("Attempt to pop empty clip stack")
+    end
+
+    if #drawContext.clipStack > 0 then
+        drawContext.currentClip = table.remove(drawContext.clipStack)
+    else
+        drawContext.currentClip = nil
+    end
+
+    iui.graphics.clip()
+end
+
+--- @return number? x, number? y, number? w, number? h
+function draw.getClipBounds()
+    local currentClip = getDrawContext().currentClip
+    if currentClip then
+        return currentClip[1], currentClip[2], currentClip[3], currentClip[4]
+    else
+        return
+    end
+end
+
+--- @param x number
+--- @param y number
+--- @param w number
+--- @param h number
+function draw.panelBackground(x, y, w, h)
+    if iui.idiom ~= "vr" then
+        iui.graphics.rectangle(x, y, w, h)
+        return
+    end
+
+    local ww, wh = iui.layout.windowWidth, iui.layout.windowHeight
+    local radius = iui.style["vrWindowCornerRadius"]
+    local bx, by, bw, bh = x, y, w, h
+    local insetCount = 0
+
+    if x > 0 then
+        insetCount = insetCount + 1
+        bx = bx - radius
+        bw = bw + radius
+    end
+
+    if y > 0 then
+        insetCount = insetCount + 1
+        by = by - radius
+        bh = bh + radius
+    end
+
+    if x + w < ww then
+        insetCount = insetCount + 1
+        bw = bw + radius
+    end
+
+    if y + h < wh then
+        insetCount = insetCount + 1
+        bh = bh + radius
+    end
+
+    if insetCount == 4 then
+        iui.graphics.rectangle(x, y, w, h)
+    else
+        iui.graphics.clip(x, y, w, h)
+        iui.graphics.rectangle(bx, by, bw, bh, radius, radius)
+        iui.graphics.clip()
+    end
+end
+
+iui.draw = draw

src/lovr/lib/iui/id.lua

@@ -0,0 +1,136 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+
+--- @class IUILib
+local iui = require(currentPath .. "iui")
+
+--- @type table<number, table<string, number>>
+local cache = {}
+local cacheMetatable = { __mode = "k" }
+
+--- @type number[]
+local stack = {}
+
+--- @type IUISet<number>
+local check = iui.set.new()
+
+function iui.resetIDCheck()
+    check:removeAll()
+end
+
+--- @param name string
+--- @param canFocus? boolean
+--- @return number
+function iui.beginID(name, canFocus)
+    if canFocus == nil then
+        canFocus = true
+    end
+
+    if iui.isDisabled() then
+        canFocus = false
+    end
+
+    -- Initialize the hash to either the current hash, or the default.
+    local stackSize = #stack
+    local hash = stackSize > 0 and stack[stackSize] or 2166136261
+
+    -- Find the cached ids for the current top id.
+    local ids = cache[hash]
+    if ids == nil then
+        ids = setmetatable({}, cacheMetatable)
+        cache[hash] = ids
+    end
+
+    -- If there's a cached hash, use it, otherwise calculate it.
+    local cached = ids[name]
+    if cached then
+        hash = cached
+    else
+        for idx = 1, #name do
+            hash = bit.bxor(hash, string.byte(name, idx))
+            hash = (hash * 16777619) % 0x100000000
+        end
+        ids[name] = hash
+    end
+
+    if check:has(hash) then
+        print("Warning: duplicate hash for " .. name)
+    else
+        check:put(hash)
+    end
+
+    -- Push the hash onto the stack.
+    table.insert(stack, hash)
+
+    -- Take focus if nothing else has it, and we're in the desktop idiom.
+    if canFocus and iui.idiom == "desktop" then
+        iui.layer.setFocusID(iui.layer.getFocusID() or hash)
+    end
+
+    if iui.layer.getFocusID() == hash and iui.input.keyboard.pressed["tab"] then
+        if iui.input.keyboard.down:has("lshift") then
+            iui.layer.setFocusID(iui.layer.getLastID())
+        else
+            iui.layer.setFocusID(nil)
+        end
+        iui.input.keyboard.pressed["tab"] = nil
+    end
+
+    if canFocus then
+        iui.layer.setLastID(hash)
+    end
+
+    return hash
+end
+
+--- @param advanceLayout? boolean
+function iui.endID(advanceLayout)
+    table.remove(stack)
+
+    if advanceLayout == nil or advanceLayout then
+        iui.layout.advance()
+    end
+end
+
+--- Attempts to set the current ID as the hover ID.
+---
+--- An ID won't become the hover ID if another ID is the current active ID, or
+--- if the control is disabled.
+function iui.becomeHover()
+    if iui.isDisabled() then
+        return
+    end
+
+    local id = stack[#stack]
+    if iui.activeID == nil or iui.activeID == id then
+        iui.hoverID = id
+    end
+end
+
+--- @param id? number
+function iui.becomeActive(id)
+    if not iui.isDisabled() then
+        if iui.activeID and iui.widgetDeactivated then
+            iui.widgetDeactivated()
+        end
+
+        id = id or stack[#stack]
+        iui.activeID = id
+        iui.hadActiveID = true
+
+        if iui.widgetActivated then
+            iui.widgetActivated()
+        end
+    end
+end
+
+function iui.becomeFocus()
+    if not iui.isDisabled() then
+        iui.layer.setFocusID(stack[#stack])
+    end
+end
+
+--- @param id number
+--- @return boolean
+function iui.isFocused(id)
+    return iui.layer.isTop() and iui.layer.getFocusID() == id
+end

src/lovr/lib/iui/init.lua

@@ -0,0 +1,25 @@
+local currentPath = (...):gsub('%.init$', '') .. "."
+local resourcePath = currentPath:gsub("%.", "/")
+
+--- @type IUILib
+local iui = require(currentPath .. "iui")
+
+iui.resourcePath = resourcePath
+
+require(currentPath .. "utils")
+require(currentPath .. "set")
+require(currentPath .. "pool")
+require(currentPath .. "window-manager")
+require(currentPath .. "color")
+require(currentPath .. "input")
+require(currentPath .. "id")
+require(currentPath .. "draw")
+require(currentPath .. "draw-queue")
+require(currentPath .. "layout")
+require(currentPath .. "style")
+require(currentPath .. "state")
+require(currentPath .. "layer")
+
+require(currentPath .. "widgets")
+
+return iui

src/lovr/lib/iui/input/init.lua

@@ -0,0 +1,61 @@
+local currentPath = (...):gsub('%.init$', '') .. "."
+local parentPath = currentPath:match('(.-)[^%./]+%.$')
+
+--- @class IUILib
+local iui = require(parentPath .. "iui")
+
+--- @class IUIInput
+local input = require(currentPath .. "input")
+
+--- @class (exact) IUIInputRootContext
+--- @field textBuffer string?
+--- @field isActive boolean
+
+--- @type IUIInputRootContext
+local ctx
+
+function input.load()
+    ctx = {
+        textBuffer = nil,
+        isActive = true,
+    }
+
+    input.keyboard.load()
+end
+
+function input.text(s)
+    if ctx.textBuffer then
+        ctx.textBuffer = ctx.textBuffer .. s
+    else
+        ctx.textBuffer = s
+    end
+
+    if ctx.isActive then
+        input.textBuffer = ctx.textBuffer
+    else
+        input.textBuffer = nil
+    end
+end
+
+function input.endFrame()
+    input.mouse.endFrame()
+    input.keyboard.endFrame()
+
+    ctx.textBuffer = nil
+    input.textBuffer = nil
+end
+
+--- @param active boolean
+function input.setActive(active)
+    ctx.isActive = active
+    input.mouse.setActive(active)
+    input.keyboard.setActive(active)
+
+    if active then
+        input.textBuffer = ctx.textBuffer
+    else
+        input.textBuffer = nil
+    end
+end
+
+iui.input = input

src/lovr/lib/iui/input/input.lua

@@ -0,0 +1,45 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+
+--- @class IUIInput
+local input = {
+    --- @type string?
+    textBuffer = nil
+}
+
+--- @alias IUIMouseEvent "move" | "down" | "up" | "scroll"
+
+--- @class IUIMouse
+--- @field x number
+--- @field y number
+--- @field dx number
+--- @field dy number
+--- @field scrollX number
+--- @field scrollY number
+--- @field down IUISet<number>
+--- @field pressed IUISet<number>
+--- @field released IUISet<number>
+--- @field newRootContext fun(): IUIMouseRootContext
+--- @field setRootContext fun(rootContext: IUIMouseRootContext)
+--- @field endFrame fun()
+--- @field resetVelocity fun()
+--- @field getVelocity fun(): number, number
+--- @field setActive fun(active: boolean)
+--- @overload fun(event: IUIMouseEvent, button: number, x: number, y: number, dx: number, dy: number)
+
+--- @class IUIKeyboard
+--- @field down IUISet<string>
+--- @field pressed table<string, IUIKeyPressed>
+--- @field released IUISet<string>
+--- @field load fun()
+--- @field endFrame fun()
+--- @field setActive fun(active: boolean)
+--- @field getPrimaryModifierKeycode fun(): string
+--- @overload fun(event: IUIKeyEvent, keycode: string, isRepeat: boolean)
+
+--- @type IUIMouse
+input.mouse = require(currentPath .. "mouse")
+
+--- @type IUIKeyboard
+input.keyboard = require(currentPath .. "keyboard")
+
+return input

src/lovr/lib/iui/input/keyboard.lua

@@ -0,0 +1,79 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+local parentPath = currentPath:match('(.-)[^%./]+%.$')
+
+--- @class IUILib
+local iui = require(parentPath .. "iui")
+
+--- @alias IUIKeyEvent "down" | "up"
+
+--- @alias IUIKeyPressed { isRepeat: boolean }
+
+--- @class (exact) IUIKeyboardState
+--- @field down IUISet<string>
+--- @field pressed table<string, IUIKeyPressed>
+--- @field released IUISet<string>
+
+--- @class (exact) IUIKeyboardRootContext
+--- @field storage IUIKeyboardState
+--- @field disabledStorage IUIKeyboardState
+
+--- @return IUIKeyboardState
+local function makeKeyboardState()
+    return {
+        down = iui.set.new(),
+        pressed = {},
+        released = iui.set.new()
+    }
+end
+
+local ctx --- @type IUIKeyboardRootContext
+
+local keyboard = {
+    --- @param event IUIKeyEvent
+    --- @param keycode string
+    --- @param isRepeat boolean
+    __call = function(_, event, keycode, isRepeat)
+        if event == "down" then
+            ctx.storage.down:put(keycode)
+            ctx.storage.pressed[keycode] = { isRepeat = isRepeat }
+        elseif event == "up" then
+            ctx.storage.down:remove(keycode)
+            ctx.storage.released:put(keycode)
+        end
+    end
+}
+setmetatable(keyboard, keyboard)
+
+function keyboard.load()
+    ctx = {
+        storage = makeKeyboardState(),
+        disabledStorage = makeKeyboardState()
+    }
+
+    keyboard.__index = ctx.storage
+end
+
+function keyboard.endFrame()
+    local pressed = ctx.storage.pressed
+    for k, _ in pairs(pressed) do
+        pressed[k] = nil
+    end
+
+    ctx.storage.released:removeAll()
+end
+
+--- @param active boolean
+function keyboard.setActive(active)
+    keyboard.__index = active and ctx.storage or ctx.disabledStorage
+end
+
+--- @return string keycode
+function keyboard.getPrimaryModifierKeycode()
+    if iui.backend.system.getOS() == "macOS" then
+        return "lgui"
+    else
+        return "lctrl"
+    end
+end
+
+return keyboard --[[@as IUIKeyboard]]

src/lovr/lib/iui/input/mouse.lua

@@ -0,0 +1,159 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+local parentPath = currentPath:match('(.-)[^%./]+%.$')
+
+--- @class IUILib
+local iui = require(parentPath .. "iui")
+
+--- @class (exact) IUIMouseVelocityEntry
+--- @field dx number
+--- @field dy number
+--- @field timestamp number
+--- @field dt number
+
+--- @class (exact) IUIMouseState
+--- @field x number
+--- @field y number
+--- @field dx number
+--- @field dy number
+--- @field scrollX number
+--- @field scrollY number
+--- @field down IUISet<number>
+--- @field pressed IUISet<number>
+--- @field released IUISet<number>
+
+--- @class (exact) IUIMouseRootContext
+--- @field velocityBuffer IUIMouseVelocityEntry[]
+--- @field storage IUIMouseState
+--- @field disabledStorage IUIMouseState
+
+local ctx --- @type IUIMouseRootContext
+
+local function limitMouseVelocityEvents()
+    local limit = iui.backend.system.getTimestamp() - 0.1
+
+    while #ctx.velocityBuffer > 0 and ctx.velocityBuffer[1].timestamp < limit do
+        table.remove(ctx.velocityBuffer, 1)
+    end
+end
+
+local function addMouseVelocityEvent(dx, dy)
+    local timestamp = iui.backend.system.getTimestamp()
+
+    --- @type IUIMouseVelocityEntry
+    local entry = { dx = dx, dy = dy, timestamp = timestamp, dt = iui.dt }
+
+    table.insert(ctx.velocityBuffer, entry)
+
+    limitMouseVelocityEvents()
+end
+
+--- @return IUIMouseState
+local function makeMouseState()
+    --- @type IUIMouseState
+    return {
+        x = -100,
+        y = -100,
+        dx = 0,
+        dy = 0,
+        scrollX = 0,
+        scrollY = 0,
+        down = iui.set.new(),
+        pressed = iui.set.new(),
+        released = iui.set.new()
+    }
+end
+
+local mouse = {
+    --- @param event IUIMouseEvent
+    --- @param button number
+    --- @param x number
+    --- @param y number
+    --- @param dx number
+    --- @param dy number
+    __call = function(_, event, button, x, y, dx, dy)
+        if ctx == nil then return end
+        local storage = ctx.storage
+
+        if event == "move" then
+            storage.x = x
+            storage.y = y
+            storage.dx = storage.dx + dx
+            storage.dy = storage.dy + dy
+            addMouseVelocityEvent(dx, dy)
+        elseif event == "down" then
+            storage.x = x
+            storage.y = y
+            storage.down:put(button)
+            storage.pressed:put(button)
+        elseif event == "up" then
+            storage.x = x
+            storage.y = y
+            storage.down:remove(button)
+            storage.released:put(button)
+        elseif event == "scroll" then
+            storage.scrollX = storage.scrollX + dx
+            storage.scrollY = storage.scrollY + dy
+        end
+    end,
+}
+setmetatable(mouse, mouse)
+
+--- @return IUIMouseRootContext
+function mouse.newRootContext()
+    --- @type IUIMouseRootContext
+    return {
+        velocityBuffer = {},
+        storage = makeMouseState(),
+        disabledStorage = makeMouseState()
+    }
+end
+
+--- @param rootContext IUIMouseRootContext
+function mouse.setRootContext(rootContext)
+    ctx = rootContext
+
+    mouse.__index = ctx.storage
+end
+
+function mouse.endFrame()
+    local storage = ctx.storage
+
+    storage.dx = 0
+    storage.dy = 0
+    storage.scrollX = 0
+    storage.scrollY = 0
+    storage.pressed:removeAll()
+    storage.released:removeAll()
+end
+
+function mouse.resetVelocity()
+    ctx.velocityBuffer = {}
+end
+
+--- @return number vx, number vy
+function mouse.getVelocity()
+    local vx, vy = 0, 0
+
+    local weightSum = 0
+    local now = iui.backend.system.getTimestamp()
+
+    for _, entry in ipairs(ctx.velocityBuffer) do
+        local weight = math.exp((entry.timestamp - now) * 20)
+        weightSum = weightSum + weight
+        vx = vx + (entry.dx / entry.dt) * weight
+        vy = vy + (entry.dy / entry.dt) * weight
+    end
+
+    if weightSum ~= 0 then
+        vx, vy = vx / weightSum, vy / weightSum
+    end
+
+    return -vx, -vy
+end
+
+--- @param active boolean
+function mouse.setActive(active)
+    mouse.__index = active and ctx.storage or ctx.disabledStorage
+end
+
+return mouse --[[@as IUIMouse]]

src/lovr/lib/iui/iui.lua

@@ -0,0 +1,162 @@
+--- @class IUILib
+--- @field dt number The time since the last frame began.
+--- @field resourcePath string
+--- @field idiom IUIIdiom
+--- @field detail IUIDetail
+--- @field backend IUIBackend
+--- @field graphics IUIGraphicsBackend
+--- @field disabledCount number
+--- @field hoverID? number The ID of the widget a pointer is hovering over.
+--- @field activeID? number The ID of the widget that's being actively used.
+--- @field cursor? IUICursorName The desired mouse cursor to display.
+--- @field hadActiveID boolean Internal flag for detecting widget deactivation.
+--- @field widgetActivated? fun() A callback when a widget becomes active.
+--- @field widgetDeactivated? fun() A callback when a widget resigns active.
+local iui = {}
+
+--- @type IUICursorName?
+local currentCursor = nil
+
+--- @type table<IUICursorName, IUICursor>
+local cursors = {}
+
+--- @type IUIWindowManager
+local windowManager
+
+--- @type IUISet<IUIWindowManager>
+local processedWindowManagers
+
+local rootKeys = {
+    disabledCount = true,
+    hoverID = true,
+    activeID = true,
+    hadActiveID = true,
+    cursor = true
+}
+
+setmetatable(iui, {
+    __index = function(t, k)
+        if rootKeys[k] then
+            return windowManager[k]
+        end
+
+        return nil
+    end,
+    __newindex = function(t, k, v)
+        if rootKeys[k] then
+            windowManager[k] = v
+        else
+            rawset(t, k, v)
+        end
+    end
+})
+
+--- @param backend IUIBackend
+--- @param config? IUIConfig
+function iui.load(backend, config)
+    config = config or {}
+    backend.config(config)
+
+    iui.idiom = config.idiom or error("No idiom specified")
+    iui.detail = config.detail or error("No detail specified")
+    iui.dpi = config.dpi or backend.system.getDPI()
+
+    iui.backend = backend
+    iui.graphics = iui.drawQueue
+
+    iui.input.load()
+
+    iui.drawQueue.setBackend(backend.graphics)
+
+    backend.load(iui)
+
+    --- @type IUICursorName[]
+    local cursorNames = { "ibeam", "sizewe", "sizens" }
+    for _, name in ipairs(cursorNames) do
+        cursors[name] = iui.backend.system.getSystemCursor(name)
+    end
+
+    iui.style.load()
+end
+
+--- @param newWindowManager IUIWindowManager
+function iui.setWindowManager(newWindowManager)
+    windowManager = newWindowManager
+
+    iui.draw.setWindowManager(windowManager)
+    iui.layer.setWindowManager(windowManager)
+    iui.state.setWindowManager(windowManager)
+end
+
+--- @param dt number
+function iui.beginFrame(dt)
+    iui.dt = dt
+    processedWindowManagers = iui.set.new()
+
+    iui.backend.beginFrame(dt)
+end
+
+--- @param width number
+--- @param height number
+function iui.beginWindow(width, height)
+    --- @type IUIWindowManager
+    local manager = iui.backend.getFullscreenWindowManager()
+
+    if processedWindowManagers:has(manager) then
+        error("window manager already processed this frame")
+    end
+    processedWindowManagers:put(manager)
+
+    iui.setWindowManager(manager)
+    windowManager:beginFrame()
+
+    iui.layout.windowWidth = width
+    iui.layout.windowHeight = height
+    iui.draw.setWindowSize(width, height)
+
+    iui.layout.beginPanel(0, 0, width, height)
+end
+
+function iui.endWindow()
+    iui.layout.endPanel()
+
+    windowManager:endFrame()
+end
+
+function iui.endFrame()
+    iui.backend.endFrame()
+    iui.input.endFrame()
+
+    if currentCursor ~= iui.cursor then
+        currentCursor = iui.cursor
+
+        iui.backend.system.setCursor(cursors[currentCursor])
+    end
+end
+
+function iui.beginDisabled()
+    iui.disabledCount = iui.disabledCount + 1
+end
+
+function iui.endDisabled()
+    if iui.disabledCount == 0 then
+        error("Control disable underflow")
+    end
+
+    iui.disabledCount = iui.disabledCount - 1
+end
+
+--- @return boolean isDisabled
+function iui.isDisabled()
+    return iui.disabledCount ~= 0
+end
+
+--- @param name? IUICursorName
+--- @return IUICursor?
+function iui.getCursor(name)
+    if name then
+        return cursors[name]
+    end
+end
+
+return iui

src/lovr/lib/iui/layer.lua

@@ -0,0 +1,125 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+
+--- @class IUILib
+local iui = require(currentPath .. "iui")
+
+--- @class IUILayer
+--- @field name string
+--- @field focusID? number
+--- @field lastID? number
+local layer = {}
+
+--- @class (exact) IUILayerRootContext
+--- @field layers IUILayer[]
+--- @field newLayers IUILayer[]
+--- @field layerIndex number
+--- @field isUnwinding boolean
+
+local ctx --- @type IUILayerRootContext
+
+local function isInputActive()
+    return (#ctx.newLayers == #ctx.layers) and (not ctx.isUnwinding)
+end
+
+local function setInputActive()
+    iui.input.setActive(isInputActive())
+end
+
+--- @return IUILayer
+function layer.getCurrentLayer()
+    return ctx.newLayers[ctx.layerIndex]
+end
+
+--- @return IUILayerRootContext
+function layer.newRootContext()
+    --- @type IUILayerRootContext
+    return {
+        layers = {},
+        newLayers = {},
+        layerIndex = 0,
+        isUnwinding = false
+    }
+end
+
+--- @param windowManager IUIWindowManager
+function layer.setWindowManager(windowManager)
+    ctx = windowManager.layer
+end
+
+function layer.beginFrame()
+    ctx.layerIndex = 0
+    ctx.newLayers = {}
+    iui.beginLayer("__root")
+    setInputActive()
+end
+
+function layer.endFrame()
+    iui.endLayer()
+    ctx.layers = ctx.newLayers
+    ctx.isUnwinding = false
+end
+
+--- @return number? id
+function layer.getFocusID()
+    return layer.getCurrentLayer().focusID
+end
+
+--- @param id? number
+function layer.setFocusID(id)
+    layer.getCurrentLayer().focusID = id
+end
+
+--- @return number? id
+function layer.getLastID()
+    return layer.getCurrentLayer().lastID
+end
+
+--- @param id? number
+function layer.setLastID(id)
+    layer.getCurrentLayer().lastID = id
+end
+
+--- @return boolean
+function layer.isTop()
+    return ctx.layerIndex == #ctx.layers
+end
+
+function iui.beginLayer(name)
+    if ctx.isUnwinding then
+        error("Attempt to begin layer after having ended layers")
+    end
+
+    ctx.layerIndex = ctx.layerIndex + 1
+
+    if #ctx.newLayers < #ctx.layers then
+        local existing = ctx.layers[#ctx.newLayers + 1]
+        if existing.name == name then
+            table.insert(ctx.newLayers, existing)
+        else
+            ctx.layers = ctx.newLayers
+
+            --- @type IUILayer
+            local newLayer = { name = name }
+            table.insert(ctx.newLayers, newLayer)
+        end
+    else
+        --- @type IUILayer
+        local newLayer = { name = name }
+        table.insert(ctx.newLayers, newLayer)
+    end
+
+    setInputActive()
+    iui.draw.beginContext()
+end
+
+function iui.endLayer()
+    ctx.isUnwinding = true
+    ctx.layerIndex = ctx.layerIndex - 1
+    if ctx.layerIndex < 0 then
+        error("Layer index underflow")
+    end
+    setInputActive()
+    iui.draw.endContext()
+end
+
+iui.layer = layer

src/lovr/lib/iui/layout.lua

@@ -0,0 +1,452 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+
+--- @class IUILib
+local iui = require(currentPath .. "iui")
+
+--- @alias IUILayoutRowKind "fixed" | "dynamic" | "intrinsic" | "mixed"
+
+--- @class (exact) IUILayoutPanel
+--- @field x number
+--- @field y number
+--- @field w number
+--- @field h number
+--- @field margin number
+--- @field rowHeight number
+--- @field rowKind IUILayoutRowKind
+--- @field rowData any
+--- @field intrinsicDefault? number
+--- @field intrinsicLimit? number
+--- @field rowY number
+--- @field columnX number
+--- @field wantsIntrinsicWidth boolean
+--- @field wantsIntrinsicHeight boolean
+--- @field intrinsicWidth? number
+--- @field intrinsicHeight? number
+--- @field columnIndex number
+--- @field columnCountCache? number
+--- @field columnBoundsCache? IUIColumnXBounds[]
+--- @field zStackCount? number
+--- @field contentWidth number
+--- @field contentHeight number
+
+--- @class (exact) IUIColumnXBounds
+--- @field x number
+--- @field w number
+
+--- @class (exact) IUILayoutColumn
+--- @field kind "fixed" | "dynamic"
+--- @field size number
+
+--- @class IUILayout
+--- @field windowWidth number
+--- @field windowHeight number
+local layout = {}
+
+--- @type IUILayoutPanel[]
+local panels = {}
+
+function layout.beginFrame()
+
+end
+
+function layout.endFrame()
+    if #panels ~= 0 then
+        error("Unbalanced panel stack: expected 0, got " .. #panels)
+    end
+end
+
+--- @return number rowHeight
+function layout.getDefaultRowHeight()
+    local padding = iui.style["padding"]
+    local fontHeight = math.floor(iui.style["font"]:getHeight())
+    local rowHeight = fontHeight + padding * 2
+
+    return rowHeight
+end
+
+--- @param panel IUILayoutPanel
+local function resetColumnBoundsCache(panel)
+    if panel.columnBoundsCache ~= nil then
+        iui.pool.put(panel.columnBoundsCache)
+        panel.columnBoundsCache = nil
+    end
+end
+
+--- @param x number
+--- @param y number
+--- @param w number
+--- @param h number
+--- @param margin? number
+--- @return IUILayoutPanel
+function layout.beginPanel(x, y, w, h, margin)
+    margin = margin or iui.style["margin"]
+
+    local rowHeight = layout.getDefaultRowHeight()
+
+    --- @type IUILayoutPanel
+    local panel = iui.pool.get("layout_panel")
+
+    panel.x = x
+    panel.y = y
+    panel.w = w
+    panel.h = h
+    panel.margin = margin
+    panel.rowHeight = rowHeight
+    panel.rowY = margin
+    panel.columnX = margin
+    panel.wantsIntrinsicWidth = false
+    panel.wantsIntrinsicHeight = false
+    panel.columnIndex = 1
+    panel.rowKind = "dynamic"
+    panel.rowData = 1
+    panel.intrinsicDefault = nil
+    panel.intrinsicLimit = nil
+    panel.contentWidth = 0
+    panel.contentHeight = 0
+
+    panel.intrinsicWidth = nil
+    panel.intrinsicHeight = nil
+    panel.columnCountCache = nil
+    panel.zStackCount = nil
+
+    resetColumnBoundsCache(panel)
+
+    table.insert(panels, panel)
+
+    return panel
+end
+
+--- @param advance? boolean
+function layout.endPanel(advance)
+    local panel = layout.getPanel()
+    if panel.zStackCount ~= nil and panel.zStackCount ~= 0 then
+        error(
+            "Unbalanced panel zstack count: expected 0, got " ..
+            panel.zStackCount
+        )
+    end
+
+    table.remove(panels)
+
+    iui.pool.put(panel)
+
+    if advance == true or (#panels > 0 and advance ~= false) then
+        iui.layout.advance()
+    end
+end
+
+--- @param index? number
+function layout.getPanel(index)
+    return panels[index or #panels]
+end
+
+--- @return number w, number h
+function layout.getContentSize()
+    local panel = layout.getPanel()
+    return panel.contentWidth, panel.contentHeight
+end
+
+--- @return boolean wantsIntrinsicWidth, boolean wantsIntrinsicHeight
+function layout.getWantsIntrinsic()
+    local panel = layout.getPanel()
+    return panel.wantsIntrinsicWidth, panel.wantsIntrinsicHeight
+end
+
+--- @param w number
+function layout.setIntrinsicWidth(w)
+    local panel = layout.getPanel()
+    panel.intrinsicWidth = w
+end
+
+--- @param h number
+function layout.setIntrinsicHeight(h)
+    local panel = layout.getPanel()
+    panel.intrinsicHeight = h
+end
+
+--- @param rowHeight? number
+--- @return IUILayoutPanel
+local function beginRowCommon(rowHeight)
+    if rowHeight == nil then
+        rowHeight = layout.getDefaultRowHeight()
+    end
+
+    local panel = layout.getPanel()
+
+    if panel.columnIndex ~= 1 then
+        panel.columnIndex = 1
+        panel.rowY = panel.rowY + panel.rowHeight + iui.style["spacing"]
+    end
+
+    panel.wantsIntrinsicHeight = false
+    panel.wantsIntrinsicWidth = false
+    panel.intrinsicWidth = nil
+    panel.intrinsicHeight = nil
+    panel.rowHeight = rowHeight
+    panel.columnCountCache = nil
+    resetColumnBoundsCache(panel)
+
+    return panel
+end
+
+--- @param count? number
+--- @param rowHeight? number
+function layout.beginDynamicRow(count, rowHeight)
+    local panel = beginRowCommon(rowHeight)
+    panel.rowKind = "dynamic"
+    panel.rowData = count or 1
+end
+
+--- @param size number
+--- @param rowHeight? number
+function layout.beginFixedRow(size, rowHeight)
+    local panel = beginRowCommon(rowHeight)
+    panel.rowKind = "fixed"
+    panel.rowData = size
+end
+
+--- @param default? number
+--- @param limit? number
+--- @param rowHeight? number
+function layout.beginIntrinsicRow(default, limit, rowHeight)
+    local panel = beginRowCommon(rowHeight)
+    panel.rowKind = "intrinsic"
+    panel.wantsIntrinsicWidth = true
+    panel.intrinsicDefault = default
+    panel.intrinsicLimit = limit
+end
+
+--- @param columns IUILayoutColumn[]
+--- @param rowHeight? number
+function layout.beginMixedRow(columns, rowHeight)
+    local panel = beginRowCommon(rowHeight)
+    panel.rowKind = "mixed"
+    panel.rowData = columns
+end
+
+--- Begins a row that causes the next widget to fill the remainder of the
+--- current panel.
+function layout.fillPanel()
+    local panel = layout.getPanel()
+
+    if panel.columnIndex ~= 1 then
+        panel.columnIndex = 1
+        panel.rowY = panel.rowY + panel.rowHeight + iui.style["spacing"]
+    end
+
+    local h = panel.h - (panel.rowY + panel.margin)
+    layout.beginDynamicRow(1, h)
+end
+
+function layout.beginZStack()
+    local panel = layout.getPanel()
+    panel.zStackCount = (panel.zStackCount or 0) + 1
+end
+
+--- @param advance? boolean
+function layout.endZStack(advance)
+    local panel = layout.getPanel()
+    if panel.zStackCount == nil or panel.zStackCount == 0 then
+        error("Attempt to end ZStack without one on panel")
+    end
+    panel.zStackCount = panel.zStackCount - 1
+
+    if advance then
+        iui.layout.advance()
+    end
+end
+
+--- @return number x, number y, number w, number h
+function layout.getBounds()
+    local panel = layout.getPanel()
+    local y = panel.rowY
+    local h = panel.rowHeight
+
+    local margin = panel.margin
+    local spacing = iui.style["spacing"]
+
+    local x, w = 0, 0
+    local rowKind = panel.rowKind
+    if rowKind == "fixed" then
+        w = panel.rowData
+        x = margin + (panel.columnIndex - 1) * (w + spacing)
+    elseif rowKind == "dynamic" then
+        local count = panel.rowData
+        w = (panel.w - (2 * margin + (count - 1) * spacing)) / count
+        x = margin + (panel.columnIndex - 1) * (w + spacing)
+
+        local maxX = iui.utils.round(x + w)
+        x = iui.utils.round(x)
+        w = maxX - x
+    elseif rowKind == "intrinsic" then
+        local edge = panel.w - panel.margin
+        x = panel.columnX
+        w = panel.intrinsicWidth or panel.intrinsicDefault or (edge - x)
+        if x + w > edge and panel.columnIndex ~= 1 then
+            x = panel.margin
+            panel.columnIndex = 1
+            panel.rowY = panel.rowY + panel.rowHeight + spacing
+            y = panel.rowY
+        end
+        panel.intrinsicWidth = w
+    elseif rowKind == "mixed" then
+        if panel.columnBoundsCache == nil then
+            --- The sum of dynamic column `size` values.
+            local dynamicSum = 0
+
+            --- The amount of space available to dynamic columns. This is
+            --- whatever's left over after the margin, spacing, and fixed
+            --- columns are accounted for.
+            local dynamicSpace = panel.w - margin * 2
+
+            --- @type IUILayoutColumn[]
+            local columns = panel.rowData
+
+            -- Do a first pass through the columns, calculating the dynamic sum
+            -- and space values.
+            for idx = 1, #columns do
+                if idx > 1 then
+                    dynamicSpace = dynamicSpace - spacing
+                end
+
+                local column = columns[idx]
+                if column.kind == "dynamic" then
+                    dynamicSum = dynamicSum + column.size
+                elseif column.kind == "fixed" then
+                    dynamicSpace = dynamicSpace - column.size
+                end
+            end
+
+            --- @type IUIColumnXBounds[]
+            local bounds = iui.pool.get("layout_column_bounds_cache")
+            for index, entry in ipairs(bounds) do
+                iui.pool.put(entry)
+                bounds[index] = nil
+            end
+
+            local head = margin
+            for idx = 1, #columns do
+                local column = columns[idx]
+                local colX = head
+                local colW = 0
+                if column.kind == "fixed" then
+                    colW = column.size
+                elseif column.kind == "dynamic" then
+                    colW = dynamicSpace * (column.size / dynamicSum)
+                end
+                head = head + colW + spacing
+                local maxX = colX + colW
+                colX = iui.utils.round(colX)
+                maxX = iui.utils.round(maxX)
+                colW = maxX - colX
+                --- @type IUIColumnXBounds
+                local value = iui.pool.get("layout_column_bounds_entry")
+                value.x = colX
+                value.w = colW
+
+                table.insert(bounds, value)
+            end
+
+            panel.columnBoundsCache = bounds
+        end
+
+        local bounds = panel.columnBoundsCache[panel.columnIndex]
+
+        x = bounds.x
+        w = bounds.w
+    end
+
+    x = panel.x + x
+    y = panel.y + y
+
+    panel.contentWidth = math.max(panel.contentWidth, x + w + panel.margin - panel.x)
+    panel.contentHeight = math.max(panel.contentHeight, y + h + panel.margin - panel.y)
+
+    return x, y, w, h
+end
+
+--- @param index? number
+--- @return number x, number y, number w, number h
+function layout.getPanelBounds(index)
+    local panel = layout.getPanel(index)
+
+    return panel.x, panel.y, panel.w, panel.h
+end
+
+--- @param x? number
+--- @param y? number
+--- @return boolean
+function layout.containsPoint(x, y)
+    x = x or iui.input.mouse.x
+    y = y or iui.input.mouse.y
+
+    local bx, by, bw, bh = layout.getBounds()
+    if not iui.utils.rectContains(bx, by, bw, bh, x, y) then
+        return false
+    end
+
+    local cx, cy, cw, ch = iui.draw.getClipBounds()
+    if cx then
+        if not iui.utils.rectContains(
+                cx, cy --[[@as any]], cw --[[@as any]], ch --[[@as any]], x, y
+            ) then
+            return false
+        end
+    end
+
+    return true
+end
+
+function layout.spacer()
+    layout.advance()
+end
+
+function layout.advance()
+    local panel = layout.getPanel()
+
+    if panel.zStackCount ~= nil and panel.zStackCount ~= 0 then
+        return
+    end
+
+    local spacing = iui.style["spacing"]
+
+    local rowKind = panel.rowKind
+    local count = panel.columnCountCache
+
+    if count == nil then
+        if rowKind == "fixed" then
+            local num = panel.w + spacing - panel.margin * 2
+            local den = panel.rowData + spacing
+            count = math.floor(num / den)
+            if count < 1 then
+                count = 1
+            end
+        elseif rowKind == "dynamic" then
+            count = panel.rowData
+        elseif rowKind == "mixed" then
+            count = #panel.rowData
+        end
+
+        panel.columnCountCache = count
+    end
+
+    if rowKind == "intrinsic" then
+        panel.columnIndex = panel.columnIndex + 1
+        panel.columnX = panel.columnX + spacing + (panel.intrinsicWidth or 0)
+        panel.intrinsicWidth = nil
+        panel.intrinsicHeight = nil
+
+        if panel.intrinsicLimit and panel.columnIndex >= panel.intrinsicLimit then
+            panel.columnIndex = 1
+            panel.columnX = panel.margin
+            panel.rowY = panel.rowY + panel.rowHeight + spacing
+        end
+    elseif panel.columnIndex == count then
+        panel.columnIndex = 1
+        panel.rowY = panel.rowY + panel.rowHeight + spacing
+    else
+        panel.columnIndex = panel.columnIndex + 1
+    end
+end
+
+iui.layout = layout

src/lovr/lib/iui/pool.lua

@@ -0,0 +1,54 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+
+--- @class IUILib
+local iui = require(currentPath .. "iui")
+
+--- @class IUIPool
+local pool = {}
+
+--- @class (exact) IUIPoolStack
+--- @field top number
+--- @field items any[]
+
+--- @type table<string, IUIPoolStack>
+local entries = {}
+
+--- @param typename string
+--- @return IUIPoolStack
+local function getPool(typename)
+    local out = entries[typename]
+
+    if not out then
+        out = { top = 0, items = {} }
+        entries[typename] = out
+    end
+
+    return out
+end
+
+--- @generic T
+--- @param typename string
+--- @return T object
+function pool.get(typename)
+    local stack = getPool(typename)
+
+    if stack.top == 0 then
+        return {
+            _typename = typename
+        }
+    else
+        local value = stack.items[stack.top]
+        stack.top = stack.top - 1
+        return value
+    end
+end
+
+--- @generic T
+--- @param obj T
+function pool.put(obj)
+    local stack = getPool(obj["_typename"])
+    stack.top = stack.top + 1
+    stack.items[stack.top] = obj
+end
+
+iui.pool = pool

src/lovr/lib/iui/set.lua

@@ -0,0 +1,63 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+
+--- @class IUILib
+local iui = require(currentPath .. "iui")
+
+--- A type that stores an unordered collection of unique values.
+--- @class IUISet<T>
+--- @field private storage table<T, true>
+--- @field new fun(): IUISet<T> Returns a new set.
+--- @field put fun(self: self, v: T) Inserts `v`, if not already present.
+--- @field putAll fun(self: self, s: IUISet<T>) Inserts all members of `s`.
+--- @field remove fun(self: self, v: T) Removes `v`, if present.
+--- @field removeAll fun(self: self) Removes all values.
+--- @field has fun(self: self, v: T): boolean Returns whether the set has `v`.
+--- @field getCount fun(self: self): number Returns the number of values, in O(n) time.
+local Set = {}
+Set.__index = Set
+
+function Set.new()
+    local out = {
+        storage = {}
+    }
+
+    setmetatable(out, Set)
+
+    return out
+end
+
+function Set:put(v)
+    self.storage[v] = true
+end
+
+function Set:putAll(s)
+    local storage = self.storage
+    for k, _ in pairs(s.storage) do
+        storage[k] = true
+    end
+end
+
+function Set:remove(v)
+    self.storage[v] = nil
+end
+
+function Set:removeAll()
+    local storage = self.storage
+    for k, _ in pairs(storage) do
+        storage[k] = nil
+    end
+end
+
+function Set:has(v)
+    return self.storage[v] == true
+end
+
+function Set:getCount()
+    local count = 0
+    for _ in pairs(self.storage) do
+        count = count + 1
+    end
+    return count
+end
+
+iui.set = Set

src/lovr/lib/iui/state.lua

@@ -0,0 +1,46 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+
+--- @class IUILib
+local iui = require(currentPath .. "iui")
+
+--- @class IUIState
+--- @overload fun(id: number): table
+local state = {}
+
+--- @class (exact) IUIStateRootContext
+--- @field previousStates? table<number, table>
+--- @field currentStates? table<number, table>
+
+local ctx --- @type IUIStateRootContext
+
+setmetatable(state --[[@as any]], {
+    --- @param id number
+    --- @return table
+    __call = function(_, id)
+        local out = (ctx.previousStates and ctx.previousStates[id]) or {}
+        ctx.currentStates[id] = out
+        return out
+    end
+})
+
+--- @return IUIStateRootContext
+function state.newRootContext()
+    --- @type IUIStateRootContext
+    return {}
+end
+
+--- @param windowManager IUIWindowManager
+function state.setWindowManager(windowManager)
+    ctx = windowManager.state
+end
+
+function state.beginFrame()
+    ctx.currentStates = {}
+end
+
+function state.endFrame()
+    ctx.previousStates = ctx.currentStates
+    ctx.currentStates = nil
+end
+
+iui.state = state

src/lovr/lib/iui/style.lua

@@ -0,0 +1,66 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+
+--- @class IUILib
+local iui = require(currentPath .. "iui")
+
+--- @class IUIStyle
+local style = {
+    default = {
+        spacing = 8,
+        margin = 8,
+        padding = 8,
+        scrollSize = 16,
+        vrWindowCornerRadius = 16,
+    },
+}
+
+local stack = {
+    style.default
+}
+
+function style.load()
+    style.default.font = iui.graphics.newFont(12, "normal", iui.dpi)
+end
+
+function style.beginFrame()
+    style.push()
+end
+
+function style.endFrame()
+    style.pop()
+
+    if #stack ~= 1 then
+        error("Unbalanced style stack: expected 1, got " .. #stack)
+    end
+end
+
+function style.push()
+    local entry = iui.pool.get("style_stack_entry")
+    for key, _ in pairs(entry) do
+        if key ~= "_typename" then
+            entry[key] = nil
+        end
+    end
+
+    table.insert(stack, entry)
+end
+
+function style.pop()
+    iui.pool.put(table.remove(stack))
+end
+
+setmetatable(style, {
+    __index = function(_, k)
+        for idx = #stack, 1, -1 do
+            if stack[idx][k] then
+                return stack[idx][k]
+            end
+        end
+        return nil
+    end,
+    __newindex = function(_, k, v)
+        stack[#stack][k] = v
+    end
+})
+
+iui.style = style

src/lovr/lib/iui/types/backend/backend.t.lua

@@ -0,0 +1,29 @@
+--- @meta _
+
+--- @class IUICursor
+
+--- @alias IUICursorName "ibeam" | "sizewe" | "sizens"
+
+--- @class IUIBackend
+--- @field system IUISystemBackend
+--- @field graphics IUIGraphicsBackend
+local backend = {}
+
+--- @param config IUIConfig
+function backend.config(config)
+end
+
+--- @param lib IUILib
+function backend.load(lib)
+end
+
+--- @param dt number
+function backend.beginFrame(dt)
+end
+
+function backend.endFrame()
+end
+
+--- @return IUIWindowManager
+function backend.getFullscreenWindowManager()
+end

src/lovr/lib/iui/types/backend/graphics.t.lua

@@ -0,0 +1,109 @@
+--- @meta _
+
+--- @alias IUIImageFilter "nearest" | "smooth" | "linear"
+
+--- @class IUIImage9Slice
+--- @field image any
+--- @field l number
+--- @field t number
+--- @field r number
+--- @field b number
+
+--- @class IUILayeredImageItem
+--- @field image any
+--- @field color IUIColor
+
+--- @alias IUILayeredImage IUILayeredImageItem[]
+
+--- @class IUIGraphicsBackend
+local graphics = {}
+
+--- @param width number
+--- @param height number
+function graphics.beginDraw(width, height)
+end
+
+function graphics.endDraw()
+end
+
+function graphics.newFont(size, hinting, dpiscale)
+end
+
+--- @return number w, number h
+function graphics.getImageDimensions(image)
+end
+
+--- @param x number
+--- @param y number
+--- @param w number
+--- @param h number
+function graphics.clip(x, y, w, h)
+end
+
+function graphics.clip()
+end
+
+--- @param r number
+--- @param g number
+--- @param b number
+--- @param a? number
+function graphics.setColor(r, g, b, a)
+end
+
+--- @param x number
+--- @param y number
+--- @param w number
+--- @param h number
+--- @param rx? number
+--- @param ry? number
+function graphics.rectangle(x, y, w, h, rx, ry)
+end
+
+--- @param x number
+--- @param y number
+--- @param r number
+function graphics.circle(x, y, r)
+end
+
+function graphics.setFont(f)
+end
+
+--- @param s string
+--- @param x number
+--- @param y number
+function graphics.print(s, x, y)
+end
+
+--- @param image any
+--- @param filter IUIImageFilter
+--- @param x number
+--- @param y number
+--- @param w number
+--- @param h number
+function graphics.image(image, filter, x, y, w, h)
+end
+
+--- @param image any
+--- @param x number
+--- @param y number
+--- @param w number
+--- @param h number
+function graphics.msdfImage(image, x, y, w, h)
+end
+
+--- @param nineSlice IUIImage9Slice
+--- @param filter IUIImageFilter
+--- @param x number
+--- @param y number
+--- @param w number
+--- @param h number
+function graphics.nineSlice(nineSlice, filter, x, y, w, h)
+end
+
+--- @param nineSlice IUIImage9Slice
+--- @param x number
+--- @param y number
+--- @param w number
+--- @param h number
+function graphics.msdfNineSlice(nineSlice, x, y, w, h)
+end

src/lovr/lib/iui/types/backend/system.t.lua

@@ -0,0 +1,37 @@
+--- @meta _
+
+--- @class IUISystemBackend
+local system = {}
+
+--- Returns the name of the host operating system.
+---
+--- Valid responses include, but are not limited to, "Windows", "macOS",
+--- "Linux", "Android", and "iOS".
+---
+--- @return string
+function system.getOS()
+end
+
+--- @return number timestamp
+function system.getTimestamp()
+end
+
+--- @param name IUICursorName
+--- @return IUICursor
+function system.getSystemCursor(name)
+end
+
+--- @param cursor IUICursor
+function system.setCursor(cursor)
+end
+
+--- @param name string
+function system.getMSDFImage(name)
+end
+
+--- @return number dpi
+function system.getDPI()
+end
+
+function system.quit()
+end

src/lovr/lib/iui/types/config.t.lua

@@ -0,0 +1,9 @@
+--- @meta _
+
+--- @alias IUIIdiom "vr" | "desktop"
+--- @alias IUIDetail "low" | "high"
+
+--- @class IUIConfig
+--- @field idiom? IUIIdiom
+--- @field detail? IUIDetail
+--- @field dpi? number

src/lovr/lib/iui/utils.lua

@@ -0,0 +1,151 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+
+--- @class IUILib
+local iui = require(currentPath .. "iui")
+
+--- @class IUIUtils
+local utils = {}
+
+--- Returns 1 if `n` is positive, -1 if negative, and 0 if zero.
+--- @param n number
+--- @return number
+function utils.sign(n)
+    if n > 0 then
+        return 1
+    elseif n == 0 then
+        return 0
+    else
+        return -1
+    end
+end
+
+--- Returns `n` rounded to the nearest integer, with 0.5 rounding up.
+--- @param n number
+--- @return number
+function utils.round(n)
+    return math.floor(n + 0.5)
+end
+
+--- Returns the closest value to `n` that is neither below `low` nor above
+--- `high`.
+--- @param n number
+--- @param low number
+--- @param high number
+--- @return number
+function utils.clamp(n, low, high)
+    if n < low then
+        return low
+    elseif n > high then
+        return high
+    end
+
+    return n
+end
+
+--- @param rx number
+--- @param ry number
+--- @param rw number
+--- @param rh number
+--- @param px number
+--- @param py number
+--- @return boolean isInside
+function utils.rectContains(rx, ry, rw, rh, px, py)
+    if px < rx or py < ry then
+        return false
+    end
+
+    if px >= rx + rw or py >= ry + rh then
+        return false
+    end
+
+    return true
+end
+
+--- @param iw number
+--- @param ih number
+--- @param x number
+--- @param y number
+--- @param w number
+--- @param h number
+--- @return number x, number y, number w, number h
+function utils.aspectFit(iw, ih, x, y, w, h)
+    local aspectBounds = w / h
+    local aspectImage = iw / ih
+
+    local ox, oy, ow, oh = x, y, w, h
+
+    if aspectImage > aspectBounds then
+        oh = iui.utils.round(w / aspectImage)
+        oy = y + iui.utils.round((h - oh) / 2)
+    else
+        ow = iui.utils.round(h * aspectImage)
+        ox = x + iui.utils.round((w - ow) / 2)
+    end
+
+    return ox, oy, ow, oh
+end
+
+--- @param iw number
+--- @param ih number
+--- @param x number
+--- @param y number
+--- @param w number
+--- @param h number
+--- @return number x, number y, number w, number h
+function utils.aspectFill(iw, ih, x, y, w, h)
+    local aspectBounds = w / h
+    local aspectImage = iw / ih
+
+    local ox, oy, ow, oh = x, y, w, h
+
+    if aspectImage < aspectBounds then
+        oh = iui.utils.round(ow / aspectImage)
+        oy = y + iui.utils.round((h - oh) / 2)
+    else
+        ow = iui.utils.round(oh * aspectImage)
+        ox = x + iui.utils.round((w - ow) / 2)
+    end
+
+    return ox, oy, ow, oh
+end
+
+--- @param iw number
+--- @param ih number
+--- @param x number
+--- @param y number
+--- @param w number
+--- @param h number
+--- @return number x, number y, number w, number h
+function utils.center(iw, ih, x, y, w, h)
+    local ox, oy, ow, oh = x, y, w, h
+
+    ow, oh = iw, ih
+    ox = x + iui.utils.round((w - ow) / 2)
+    oy = y + iui.utils.round((h - oh) / 2)
+
+    return ox, oy, ow, oh
+end
+
+--- @param mode IUIImageMode
+--- @param iw number
+--- @param ih number
+--- @param x number
+--- @param y number
+--- @param w number
+--- @param h number
+--- @return number x, number y, number w, number h
+function utils.fill(mode, iw, ih, x, y, w, h)
+    if mode == "fill" then
+        return x, y, w, h
+    elseif mode == "aspectFit" then
+        return iui.utils.aspectFit(iw, ih, x, y, w, h)
+    elseif mode == "aspectFill" then
+        return iui.utils.aspectFill(iw, ih, x, y, w, h)
+    elseif mode == "center" then
+        return iui.utils.center(iw, ih, x, y, w, h)
+    else
+        error("unrecognized fillmode")
+    end
+end
+
+iui.utils = utils

src/lovr/lib/iui/widgets/button.lua

@@ -0,0 +1,95 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+local parentPath = currentPath:match('(.-)[^%./]+%.$')
+
+--- @class IUILib
+local iui = require(parentPath .. "iui")
+
+--- @param name string
+--- @return boolean
+function iui.button(name)
+    local id = iui.beginID(name)
+
+    local intrinsicW, intrinsicH = iui.layout.getWantsIntrinsic()
+
+    local pressed = false
+    local disabled = iui.isDisabled()
+
+    local font = iui.style["font"]
+    local padding = iui.style["padding"]
+
+    local textW = math.ceil(font:getWidth(name))
+    local textH = math.ceil(font:getHeight())
+
+    if intrinsicW then
+        iui.layout.setIntrinsicWidth(textW + padding * 4)
+    end
+
+    if intrinsicH then
+        iui.layout.setIntrinsicHeight(textH + padding * 2)
+    end
+
+    if iui.layout.containsPoint() then
+        iui.becomeHover()
+    end
+
+    if iui.hoverID == id and iui.input.mouse.pressed:has(1) then
+        iui.becomeActive()
+        iui.becomeFocus()
+    end
+
+    if iui.activeID == id then
+        if not iui.input.mouse.down:has(1) then
+            if iui.hoverID == id then
+                pressed = true
+            end
+
+            iui.activeID = nil
+        end
+    end
+
+    if iui.isFocused(id) then
+        if iui.input.keyboard.pressed["space"] then
+            pressed = true
+        end
+    end
+
+    local x, y, w, h = iui.layout.getBounds()
+
+    -- Outline
+    if not disabled then
+        if iui.isFocused(id) and iui.idiom ~= "vr" then
+            iui.colors.sysAccent500:set()
+        elseif (iui.activeID == id and iui.hoverID == id) or pressed then
+            iui.colors.sysGray200:set()
+        elseif iui.hoverID == id then
+            iui.colors.sysGray400:set()
+        else
+            iui.colors.sysGray300:set()
+        end
+        iui.graphics.rectangle(x, y, w, h, 8, 8)
+    end
+
+    -- Background
+    if (iui.activeID == id and iui.hoverID == id) or pressed then
+        iui.colors.sysGray50:set()
+    elseif iui.hoverID == id then
+        iui.colors.sysGray200:set()
+    else
+        iui.colors.sysGray100:set()
+    end
+    iui.graphics.rectangle(x + 1, y + 1, w - 2, h - 2, 7, 7)
+
+    if disabled then
+        iui.colors.sysGray300:set()
+    else
+        iui.colors.sysGray900:set()
+    end
+    iui.graphics.setFont(font)
+    local textX = x + iui.utils.round((w - textW) / 2)
+    local textY = y + iui.utils.round((h - textH) / 2)
+    iui.graphics.print(name, textX, textY)
+
+    iui.endID()
+
+    return pressed
+end

src/lovr/lib/iui/widgets/checkbox.lua

@@ -0,0 +1,120 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+local parentPath = currentPath:match('(.-)[^%./]+%.$')
+
+--- @class IUILib
+local iui = require(parentPath .. "iui")
+
+local checkmarkImage
+
+--- @param name string
+--- @param checked boolean
+--- @return boolean
+function iui.checkbox(name, checked)
+    if checkmarkImage == nil then
+        checkmarkImage = iui.backend.system.getMSDFImage(
+            "assets/glyph-checkmark.png"
+        )
+    end
+
+    local id = iui.beginID(name)
+
+    local intrinsicW, intrinsicH = iui.layout.getWantsIntrinsic()
+
+    local disabled = iui.isDisabled()
+
+    local font = iui.style["font"]
+    local padding = iui.style["padding"]
+
+    local textH = math.ceil(font:getHeight())
+    local size = textH + 2
+    local textX = size + padding
+
+    if intrinsicW then
+        local textW = math.ceil(font:getWidth(name))
+        iui.layout.setIntrinsicWidth(textX + textW)
+    end
+
+    if intrinsicH then
+        iui.layout.setIntrinsicHeight(size)
+    end
+
+    if iui.layout.containsPoint() then
+        iui.becomeHover()
+    end
+
+    if iui.hoverID == id and iui.input.mouse.pressed:has(1) then
+        iui.becomeActive()
+        iui.becomeFocus()
+    end
+
+    if iui.activeID == id then
+        if not iui.input.mouse.down:has(1) then
+            if iui.hoverID == id then
+                checked = not checked
+            end
+
+            iui.activeID = nil
+        end
+    end
+
+    if iui.isFocused(id) then
+        if iui.input.keyboard.pressed["space"] then
+            checked = not checked
+        end
+    end
+
+    local x, y, _, h = iui.layout.getBounds()
+
+    local textY = y + iui.utils.round((h - textH) / 2)
+    local boxY = y + iui.utils.round((h - size) / 2)
+
+    -- Outline
+    if not disabled then
+        if iui.isFocused(id) and iui.idiom ~= "vr" then
+            iui.colors.sysAccent500:set()
+        elseif iui.hoverID == id then
+            iui.colors.sysGray300:set()
+        else
+            iui.colors.sysGray200:set()
+        end
+        iui.graphics.rectangle(x, boxY, size, size, 2, 2)
+    end
+
+    -- Background
+    if (iui.hoverID == id and iui.activeID == id) or disabled then
+        iui.colors.sysGray100:set()
+    else
+        iui.colors.sysGray0:set()
+    end
+    iui.graphics.rectangle(x + 1, boxY + 1, size - 2, size - 2, 1, 1)
+
+    -- Check
+    if checked then
+        if disabled then
+            iui.colors.sysGray200:set()
+        elseif iui.hoverID == id and iui.activeID == id then
+            iui.colors.sysGray200:set()
+        elseif iui.hoverID == id then
+            iui.colors.sysGray400:set()
+        else
+            iui.colors.sysGray300:set()
+        end
+
+        iui.graphics.msdfImage(
+            checkmarkImage, x + 2, boxY + 2, size - 4, size - 4
+        )
+    end
+
+    -- Label
+    if disabled then
+        iui.colors.sysGray300:set()
+    else
+        iui.colors.sysGray900:set()
+    end
+    iui.graphics.setFont(font)
+    iui.graphics.print(name, x + textX, textY)
+
+    iui.endID()
+
+    return checked
+end

src/lovr/lib/iui/widgets/clip-view.lua

@@ -0,0 +1,16 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+local parentPath = currentPath:match('(.-)[^%./]+%.$')
+
+--- @class IUILib
+local iui = require(parentPath .. "iui")
+
+function iui.clipView()
+    local x, y, w, h = iui.layout.getBounds()
+    iui.draw.pushClip(x, y, w, h)
+    iui.layout.beginPanel(x, y, w, h)
+end
+
+function iui.endClipView()
+    iui.layout.endPanel()
+    iui.draw.popClip()
+end

src/lovr/lib/iui/widgets/divider.lua

@@ -0,0 +1,27 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+local parentPath = currentPath:match('(.-)[^%./]+%.$')
+
+--- @class IUILib
+local iui = require(parentPath .. "iui")
+
+function iui.divider()
+    local panel = iui.layout.getPanel()
+    local rowHeight = panel.rowHeight
+    panel.rowHeight = iui.utils.round(rowHeight / 4)
+    if panel.rowHeight % 2 == 0 then
+        panel.rowHeight = panel.rowHeight + 1
+    end
+
+    local x, y, w, h = iui.layout.getBounds()
+
+    -- local padding = iui.utils.round(iui.style["padding"] / 2)
+    local padding = 0
+    local top = math.floor(y + h / 2)
+
+    iui.colors.sysGray200:set()
+    local radius = (iui.detail == "high" and 0.5 or nil)
+    iui.graphics.rectangle(x + padding, top, w - padding * 2, 1, radius, radius)
+
+    iui.layout.advance()
+    panel.rowHeight = rowHeight
+end

src/lovr/lib/iui/widgets/image-9-slice.lua

@@ -0,0 +1,16 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+local parentPath = currentPath:match('(.-)[^%./]+%.$')
+
+--- @class IUILib
+local iui = require(parentPath .. "iui")
+
+--- @param image IUIImage9Slice
+function iui.image9Slice(image)
+    local x, y, w, h = iui.layout.getBounds()
+    local filter = iui.style["imageFilter"] or "linear" --- @type IUIImageFilter
+
+    iui.graphics.setColor(1, 1, 1)
+    iui.graphics.nineSlice(image, filter, x, y, w, h)
+
+    iui.layout.advance()
+end

src/lovr/lib/iui/widgets/image.lua

@@ -0,0 +1,32 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+local parentPath = currentPath:match('(.-)[^%./]+%.$')
+
+--- @class IUILib
+local iui = require(parentPath .. "iui")
+
+--- @alias IUIImageMode "fill" | "aspectFit" | "aspectFill" | "center"
+
+--- @param image any
+function iui.image(image)
+    local bx, by, bw, bh = iui.layout.getBounds()
+    local iw, ih = iui.graphics.getImageDimensions(image)
+
+    local filter = iui.style["imageFilter"] or "linear" --- @type IUIImageFilter
+    local mode = iui.style["imageMode"] or "aspectFit"  --- @type IUIImageMode
+    local clip = iui.style["imageClip"] or false        --- @type boolean
+
+    local ox, oy, ow, oh = iui.utils.fill(mode, iw, ih, bx, by, bw, bh)
+
+    if clip then
+        iui.draw.pushClip(bx, by, bw, bh)
+    end
+
+    iui.graphics.setColor(1, 1, 1)
+    iui.graphics.image(image, filter, ox, oy, ow, oh)
+
+    if clip then
+        iui.draw.popClip()
+    end
+
+    iui.layout.advance()
+end

src/lovr/lib/iui/widgets/init.lua

@@ -0,0 +1,26 @@
+local currentPath = (...):gsub('%.init$', '') .. "."
+
+require(currentPath .. "label")
+require(currentPath .. "button")
+require(currentPath .. "slider")
+require(currentPath .. "text-field")
+require(currentPath .. "checkbox")
+require(currentPath .. "radio")
+require(currentPath .. "split-view")
+require(currentPath .. "divider")
+require(currentPath .. "scroll-bar")
+require(currentPath .. "clip-view")
+require(currentPath .. "scroll-view")
+require(currentPath .. "menu-bar")
+require(currentPath .. "sub-menu")
+require(currentPath .. "menu-item")
+require(currentPath .. "progress")
+require(currentPath .. "tab-bar")
+require(currentPath .. "panel-background")
+require(currentPath .. "image")
+require(currentPath .. "image-9-slice")
+require(currentPath .. "msdf-image")
+require(currentPath .. "msdf-image-9-slice")
+require(currentPath .. "msdf-layered-image")
+require(currentPath .. "msdf-layered-image-9-slice")
+require(currentPath .. "list-view")

src/lovr/lib/iui/widgets/label.lua

@@ -0,0 +1,38 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+local parentPath = currentPath:match('(.-)[^%./]+%.$')
+
+--- @class IUILib
+local iui = require(parentPath .. "iui")
+
+function iui.label(text)
+    local intrinsicW, intrinsicH = iui.layout.getWantsIntrinsic()
+
+    local disabled = iui.isDisabled()
+    local font = iui.style["font"]
+    local padding = iui.style["padding"]
+
+    local textW = math.ceil(font:getWidth(text))
+    local textH = font:getHeight()
+
+    if intrinsicW then
+        iui.layout.setIntrinsicWidth(textW + padding * 2)
+    end
+
+    if intrinsicH then
+        iui.layout.setIntrinsicHeight(math.ceil(textH))
+    end
+
+    local x, y, w, h = iui.layout.getBounds()
+
+    if disabled then
+        iui.colors.sysGray300:set()
+    else
+        iui.colors.sysGray900:set()
+    end
+    iui.graphics.setFont(font)
+    local textX = x + iui.utils.round((w - textW) / 2)
+    local textY = y + iui.utils.round((h - textH) / 2)
+    iui.graphics.print(text, textX, textY)
+
+    iui.layout.advance()
+end

src/lovr/lib/iui/widgets/list-view.lua

@@ -0,0 +1,409 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+local parentPath = currentPath:match('(.-)[^%./]+%.$')
+
+--- @class IUILib
+local iui = require(parentPath .. "iui")
+
+--- @class (exact) IUIListViewStackItem
+--- @field manager IUIListManager
+--- @field isMouseInBounds boolean
+--- @field maxIndex number
+--- @field panel IUILayoutPanel
+--- @field spacing number
+--- @field margin number
+--- @field rowHeight number
+--- @field yOffset number
+--- @field lastX number
+--- @field lastY number
+--- @field lastW number
+--- @field lastH number
+
+--- @type IUIListViewStackItem[]
+local listStack = {}
+
+--- The amount of time, in seconds, to wait to select an item when pressing and
+--- holding in VR.
+local selectDelay = 0.2
+
+--- @class (exact) IUIListSelectionChangeMutation
+--- @field selection IUISet<number>
+--- @field rangeStartIndex? number
+--- @field rangeEndIndex? number
+
+--- @class IUIListManager: IUIScrollManager
+--- @field rowHeight? number
+--- @field margin? number
+--- @field spacing? number
+--- @field selection IUISet<number>
+--- @field rangeStartIndex? number
+--- @field rangeEndIndex? number
+--- @field allowsSelection boolean
+--- @field allowsMultipleSelection boolean
+--- @field allowsEmptySelection boolean
+--- @field selectTimer? number
+--- @field timerIndex? number
+--- @field conditionalMutation? IUIListSelectionChangeMutation
+local ListManager = {}
+ListManager.__index = ListManager
+setmetatable(ListManager, iui.ScrollManager)
+
+function ListManager:beganDragging()
+    self.selectTimer = nil
+    self.timerIndex = nil
+
+    local mutation = self.conditionalMutation
+    self.conditionalMutation = nil
+    if mutation then
+        self.selection:removeAll()
+        self.selection:putAll(mutation.selection)
+        self.rangeStartIndex = mutation.rangeStartIndex
+        self.rangeEndIndex = mutation.rangeEndIndex
+    end
+end
+
+--- Returns whether the user is holding down a modifier input that indicates
+--- they wish to add or remove single items from the selection.
+---
+--- @return boolean
+local function isHoldingSingleModifier()
+    local keyboard = iui.input.keyboard
+    local down = keyboard.down
+    local primary = keyboard.getPrimaryModifierKeycode()
+
+    return down:has(primary)
+end
+
+--- Returns whether the user is holding down a modifier input that indicates
+--- they wish to add or remove a range of items from the selection.
+---
+--- @return boolean
+local function isHoldingRangeModifier()
+    local keyboard = iui.input.keyboard
+    local down = keyboard.down
+
+    return down:has("lshift")
+end
+
+--- @param manager IUIListManager
+--- @param idx number
+--- @return IUIListSelectionChangeMutation? mutation
+local function applySelection(manager, idx, returnMutation)
+    --- @type IUIListSelectionChangeMutation?
+    local mutation = nil
+
+    local selection = manager.selection
+
+    if returnMutation then
+        mutation = {
+            selection = iui.set.new(),
+            rangeStartIndex = manager.rangeStartIndex,
+            rangeEndIndex = manager.rangeEndIndex,
+        }
+
+        mutation.selection:putAll(selection)
+    end
+
+    -- Is this row already part of the selection?
+    if selection:has(idx) then
+        local count = selection:getCount()
+
+        -- Do we have multiple items already selected?
+        if count > 1 then
+            if isHoldingSingleModifier() then
+                -- If there's multiple selected items, and the user is holding
+                -- the single item modifier, we just remove the one item.
+                selection:remove(idx)
+                manager.rangeStartIndex = nil
+                manager.rangeEndIndex = nil
+            elseif isHoldingRangeModifier() then
+                -- If there's multiple selected items, and the user is holding
+                -- the range modifier, we add a range of items, unwinding the
+                -- previous range if necessary.
+                local startIndex = manager.rangeStartIndex or 1
+                local endIndex = manager.rangeEndIndex
+
+                -- Undo the previous range.
+                if endIndex and endIndex ~= startIndex then
+                    local sign = iui.utils.sign(endIndex - startIndex)
+                    for index = startIndex, endIndex, sign do
+                        selection:remove(index)
+                    end
+                end
+
+                -- Add the new range.
+                local sign = iui.utils.sign(idx - startIndex)
+                if sign == 0 then
+                    selection:put(idx)
+                else
+                    for index = startIndex, idx, sign do
+                        selection:put(index)
+                    end
+                end
+
+                manager.rangeEndIndex = idx
+            else
+                -- If there's multiple items in the range, the user's clicking
+                -- a selected item, and they're not holding any modifiers, we
+                -- replace the entire selection with just this item.
+                selection:removeAll()
+                selection:put(idx)
+                manager.rangeStartIndex = idx
+                manager.rangeEndIndex = nil
+            end
+        elseif manager.allowsEmptySelection then
+            -- If this row is selected, and it's the only item in the selection,
+            -- we can only remove it if we're allowed to have an empty
+            -- selection.
+            selection:remove(idx)
+            manager.rangeStartIndex = nil
+            manager.rangeEndIndex = nil
+        end
+    else
+        -- This row is not selected, so we need to add it to the selection.
+
+        if manager.allowsMultipleSelection and isHoldingSingleModifier() then
+            -- Multiple selection is allowed, and the single item modifier is
+            -- held, so we just add the current index.
+            selection:put(idx)
+
+            manager.rangeStartIndex = idx
+            manager.rangeEndIndex = nil
+        elseif manager.allowsMultipleSelection and isHoldingRangeModifier() then
+            -- Multiple selection is allowed, and the range modifier is held, so
+            -- we add a range of items, unwinding the previous range if
+            -- necessary.
+            local startIndex = manager.rangeStartIndex or 1
+            local endIndex = manager.rangeEndIndex
+
+            -- Undo the previous range.
+            if endIndex and endIndex ~= startIndex then
+                local sign = iui.utils.sign(endIndex - startIndex)
+                for index = startIndex, endIndex, sign do
+                    selection:remove(index)
+                end
+            end
+
+            -- Add the new range.
+            local sign = iui.utils.sign(idx - startIndex)
+            if sign == 0 then
+                selection:put(idx)
+            else
+                for index = startIndex, idx, sign do
+                    selection:put(index)
+                end
+            end
+
+            manager.rangeEndIndex = idx
+        else
+            -- Either multiple selection is disallowed, or no modifier is held,
+            -- so replace the entire selection with this index.
+            selection:removeAll()
+            selection:put(idx)
+
+            manager.rangeStartIndex = idx
+            manager.rangeEndIndex = nil
+        end
+    end
+
+    return mutation
+end
+
+--- @param state IUIListViewStackItem
+--- @param idx number
+local function updateSelection(state, idx)
+    local manager = state.manager
+
+    -- Selection can only change if the list allows selection at all, and the
+    -- pointer is inside the widget.
+    if not manager.allowsSelection or not state.isMouseInBounds then
+        return
+    end
+
+    -- Did the mouse begin being pressed this frame, and has no widget
+    -- claimed the pointer?
+    --
+    -- This `if` clause here is why we do all the selection change logic at
+    -- the beginning of `listViewStep`. The *previous* row will have been
+    -- generated, and any widgets inside them will have been given the
+    -- opportunity to claim the active id.
+    if iui.activeID ~= nil or not iui.input.mouse.pressed:has(1) then
+        return
+    end
+
+    -- As a base case, this method will be called before the first row has been
+    -- generated, and we need to exit out of that case. The "last" row bounds
+    -- will not exist yet, because there hasn't been a "last" row yet.
+    local x, y, w, h = state.lastX, state.lastY, state.lastW, state.lastH
+    if not x then
+        return
+    end
+
+    -- We already know the mouse is in the list view's bounds, now we just need
+    -- to make sure it's in the row's bounds.
+    local mx, my = iui.input.mouse.x, iui.input.mouse.y
+    if not iui.utils.rectContains(x, y, w, h, mx, my) then
+        return
+    end
+
+    if iui.idiom == "vr" then
+        manager.selectTimer = selectDelay
+        manager.timerIndex = idx
+        manager.conditionalMutation = nil
+    else
+        applySelection(manager, idx, false)
+    end
+end
+
+--- @param state IUIListViewStackItem
+--- @param idx number
+local function listViewStep(state, idx)
+    updateSelection(state, idx)
+
+    idx = idx + 1
+    if idx <= state.maxIndex then
+        local manager = state.manager
+        local panel = state.panel
+        local spacing = state.spacing
+        local margin = state.margin
+        local rowHeight = state.rowHeight
+        local yOffset = state.yOffset
+
+        local spaced = rowHeight + spacing
+
+        panel.rowY = (idx - 1) * spaced + margin - yOffset
+        iui.layout.beginDynamicRow(1, rowHeight)
+
+        local x, y, w, h = iui.layout.getBounds()
+        x = x - margin
+        w = w + margin * 2
+
+        state.lastX, state.lastY, state.lastW, state.lastH = x, y, w, h
+
+        if manager.selection:has(idx) then
+            iui.colors.sysAccent500:set()
+            iui.graphics.rectangle(x, y, w, h)
+        end
+
+        return idx
+    end
+end
+
+--- @param index number
+function ListManager:scrollToIndex(index)
+    local rowHeight = self.rowHeight
+    local margin = self.margin
+    local spacing = self.spacing
+    if rowHeight == nil then
+        return
+    end
+
+    local top = margin + (index - 1) * (rowHeight + spacing)
+
+    self:scrollTo(0, top, nil, rowHeight)
+end
+
+--- @return IUIListManager
+function iui.newListManager()
+    local super = iui.newScrollManager()
+
+    --- @type IUIListManager
+    local out = setmetatable(super --[[@as any]], ListManager)
+
+    out.selection = iui.set.new()
+    out.allowsSelection = true
+    out.allowsEmptySelection = true
+    out.allowsMultipleSelection = false
+
+    return out
+end
+
+--- @param name string
+---@param count number
+---@param rowHeight? number
+---@param manager? IUIListManager
+function iui.listView(name, count, rowHeight, manager)
+    rowHeight = rowHeight or iui.layout.getDefaultRowHeight()
+    local id = iui.beginID(name, false)
+    local state = iui.state(id)
+
+    local margin = iui.style["margin"]
+    local spacing = iui.style["spacing"]
+
+    local spaced = rowHeight + spacing
+    local isMouseInBounds = iui.layout.containsPoint()
+
+    if not manager then
+        manager = state.manager
+
+        if not manager then
+            manager = iui.newListManager()
+            state.manager = manager
+        end
+    end
+
+    manager.rowHeight = rowHeight
+    manager.margin = margin
+    manager.spacing = spacing
+
+    if not iui.input.mouse.down:has(1) then
+        if manager.selectTimer then
+            applySelection(manager, manager.timerIndex, false)
+        end
+
+        manager.selectTimer = nil
+        manager.timerIndex = nil
+        manager.conditionalMutation = nil
+    end
+
+    if manager.selectTimer then
+        manager.selectTimer = manager.selectTimer - iui.dt
+        if manager.selectTimer <= 0 then
+            manager.selectTimer = nil
+            manager.conditionalMutation = applySelection(
+                manager, manager.timerIndex, true
+            )
+        end
+    end
+
+    iui.scrollView("ScrollView", manager)
+
+    --- @type IUIListViewStackItem
+    local item = iui.pool.get("list_view_stack_item")
+    table.insert(listStack, item)
+
+    if count > 0 then
+        local panel = iui.layout.getPanel()
+        local yOffset = iui.utils.round(manager.y)
+
+        panel.contentHeight = math.max(
+            panel.contentHeight, count * spaced - spacing + margin * 2 - yOffset
+        )
+
+        local minIndex = math.max(
+            math.floor((yOffset - margin) / spaced) + 1, 1
+        )
+
+        local maxIndex = math.min(
+            math.ceil((yOffset + panel.h - margin) / spaced), count
+        )
+
+        item.manager = manager
+        item.isMouseInBounds = isMouseInBounds
+        item.panel = panel
+        item.margin = margin
+        item.spacing = spacing
+        item.rowHeight = rowHeight
+        item.yOffset = yOffset
+        item.maxIndex = maxIndex
+
+        return listViewStep, item, minIndex - 1
+    end
+end
+
+function iui.endListView()
+    iui.endScrollView()
+
+    iui.endID(false)
+
+    iui.pool.put(table.remove(listStack))
+end

src/lovr/lib/iui/widgets/menu-bar.lua

@@ -0,0 +1,159 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+local parentPath = currentPath:match('(.-)[^%./]+%.$')
+
+--- @class IUILib
+local iui = require(parentPath .. "iui")
+
+--- @class IUIMenuBarStackItem
+--- @field state any
+--- @field controller IUISubMenuController
+--- @field isShowingPanel boolean
+--- @field x number
+--- @field w number
+--- @field h number
+--- @field barHeight number
+
+--- @type IUIMenuBarStackItem[]
+local itemStack = {}
+
+function iui.menuBar()
+    local x, y, w, h = iui.layout.getPanelBounds()
+
+    local barHeight = iui.layout.getDefaultRowHeight() + 1
+
+    -- Draw bar
+    iui.graphics.clip(x, y, w, barHeight)
+
+    iui.colors.sysGray100:set()
+    iui.draw.panelBackground(x, y, w, barHeight - 1)
+
+    iui.colors.sysGray200:set()
+    iui.graphics.rectangle(x, barHeight - 1, w, 1)
+
+    iui.graphics.clip()
+
+    local id = iui.beginID("__menuBar", false)
+    local state = iui.state(id)
+
+    if state.controller == nil then
+        --- @type IUISubMenuController
+        local subMenuController
+
+        subMenuController = {
+            subMenuIDs = {},
+            isMenuBar = true,
+            currentSubMenuIndex = 1,
+            panelClaimedMouseDown = false,
+            beginSubMenu = function()
+                local subMenuID = subMenuController.subMenuIDs[subMenuController.currentSubMenuIndex]
+                subMenuController.currentSubMenuIndex = subMenuController.currentSubMenuIndex + 1
+                return subMenuID
+            end,
+            endSubMenu = function()
+                subMenuController.currentSubMenuIndex = subMenuController.currentSubMenuIndex - 1
+            end,
+            setSubMenu = function(menuID)
+                local subMenuIDs = subMenuController.subMenuIDs
+                local idx = subMenuController.currentSubMenuIndex - 1
+                if state.showingSubMenuController and menuID ~= subMenuIDs[idx] then
+                    for i = idx, #subMenuIDs do
+                        table.remove(subMenuIDs, i)
+                    end
+                    table.insert(subMenuIDs, menuID)
+                end
+            end,
+            activate = function()
+                state.showingSubMenuController = true
+            end,
+            deactivate = function()
+                state.showingSubMenuController = false
+            end
+        }
+        state.controller = subMenuController
+    end
+
+    local controller = state.controller
+
+    iui.style.push()
+    iui.style["menuItemSpacing"] = iui.style["spacing"] * 4
+    iui.style["spacing"] = 0
+    iui.style["subMenuController"] = controller
+    controller.currentSubMenuIndex = 1
+    controller.panelClaimedMouseDown = false
+    controller.hoveredSubMenuIndex = nil
+
+    local isShowingPanel = state.showingSubMenuController
+    if isShowingPanel then
+        iui.beginLayer("__menuBar")
+    end
+
+    if iui.idiom == "vr" then
+        local radius = iui.style["vrWindowCornerRadius"]
+        iui.layout.beginPanel(x + radius, y, w - radius * 2, barHeight - 1, 0)
+    else
+        iui.layout.beginPanel(x, y, w, barHeight - 1, 0)
+    end
+
+    iui.layout.beginIntrinsicRow(nil, nil, barHeight - 1)
+
+    --- @type IUIMenuBarStackItem
+    local item = iui.pool.get("menu_bar_stack_item")
+    item.state = state
+    item.controller = controller
+    item.isShowingPanel = isShowingPanel
+    item.barHeight = barHeight
+    item.x = x
+    item.w = w
+    item.h = h
+
+    table.insert(itemStack, item)
+end
+
+function iui.menuBarDivider()
+    --- @type IUIMenuBarStackItem
+    local item = table.remove(itemStack)
+    local state = item.state
+    local controller = item.controller
+    local isShowingPanel = item.isShowingPanel
+    local barHeight = item.barHeight
+    local x, w, h = item.x, item.w, item.h
+
+    iui.pool.put(item)
+
+    iui.layout.endPanel()
+
+    iui.style.pop()
+
+    iui.endID(false)
+
+    if controller.hoveredSubMenuIndex and controller.hoveredSubMenuIndex < #controller.subMenuIDs then
+        state.vanishTimer = (state.vanishTimer or 0) + iui.dt
+        if state.vanishTimer > 0.35 then
+            for idx = controller.hoveredSubMenuIndex + 1, #controller.subMenuIDs do
+                table.remove(controller.subMenuIDs, idx)
+            end
+        end
+    else
+        state.vanishTimer = nil
+    end
+
+    if not state.showingSubMenuController and #controller.subMenuIDs > 0 then
+        controller.subMenuIDs = {}
+    end
+
+    if isShowingPanel then
+        if iui.input.mouse.pressed:has(1) and not controller.panelClaimedMouseDown then
+            iui.input.mouse.pressed:remove(1)
+            controller.deactivate()
+        end
+
+        iui.endLayer()
+    end
+
+    -- Content panel
+    iui.layout.beginPanel(x, barHeight, w, h - barHeight)
+end
+
+function iui.endMenuBar()
+    iui.layout.endPanel()
+end

src/lovr/lib/iui/widgets/menu-item.lua

@@ -0,0 +1,80 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+local parentPath = currentPath:match('(.-)[^%./]+%.$')
+
+--- @class IUILib
+local iui = require(parentPath .. "iui")
+
+--- @param name string
+--- @param command? string
+--- @return boolean
+function iui.menuItem(name, command)
+    if iui.idiom ~= "desktop" then
+        command = nil
+    end
+
+    local id = iui.beginID(name, false)
+
+    local intrinsicW, intrinsicH = iui.layout.getWantsIntrinsic()
+
+    local disabled = iui.isDisabled()
+    local pressed = false
+
+    local font = iui.style["font"]
+    local padding = iui.style["padding"]
+    local spacing = iui.style["menuItemSpacing"]
+
+    local nameW = math.ceil(font:getWidth(name))
+    local commandW = command and math.ceil(font:getWidth(command))
+    local textH = math.ceil(font:getHeight())
+
+    if intrinsicW then
+        if command then
+            iui.layout.setIntrinsicWidth(nameW + spacing + commandW + padding * 2)
+        else
+            iui.layout.setIntrinsicWidth(nameW + padding * 2)
+        end
+    end
+
+    if intrinsicH then
+        iui.layout.setIntrinsicHeight(textH + padding * 2)
+    end
+
+    if iui.layout.containsPoint() then
+        iui.becomeHover()
+    end
+
+    if iui.input.mouse.released:has(1) then
+        if iui.hoverID == id then
+            pressed = true
+            --- @type IUISubMenuController
+            local controller = iui.style["subMenuController"]
+            controller.deactivate()
+        end
+    end
+
+    local x, y, w, h = iui.layout.getBounds()
+    -- Background
+    if iui.hoverID == id then
+        iui.colors.sysGray200:set()
+        iui.graphics.rectangle(x + 4, y, w - 8, h, 2, 2)
+    end
+
+    if disabled then
+        iui.colors.sysGray300:set()
+    else
+        iui.colors.sysGray900:set()
+    end
+    iui.graphics.setFont(font)
+    local textX = x + padding
+    local textY = y + iui.utils.round((h - textH) / 2)
+    iui.graphics.print(name, textX, textY)
+
+    if command and commandW then
+        local commandX = x + w - padding - commandW
+        iui.graphics.print(command, commandX, textY)
+    end
+
+    iui.endID()
+
+    return pressed
+end

src/lovr/lib/iui/widgets/msdf-image-9-slice.lua

@@ -0,0 +1,18 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+local parentPath = currentPath:match('(.-)[^%./]+%.$')
+
+--- @class IUILib
+local iui = require(parentPath .. "iui")
+
+--- @param image IUIImage9Slice
+--- @param color? IUIColor
+function iui.msdfImage9Slice(image, color)
+    color = color or iui.colors.white
+
+    local x, y, w, h = iui.layout.getBounds()
+
+    color:set()
+    iui.graphics.msdfNineSlice(image, x, y, w, h)
+
+    iui.layout.advance()
+end

src/lovr/lib/iui/widgets/msdf-image.lua

@@ -0,0 +1,32 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+local parentPath = currentPath:match('(.-)[^%./]+%.$')
+
+--- @class IUILib
+local iui = require(parentPath .. "iui")
+
+--- @param image any
+--- @param color? IUIColor
+function iui.msdfImage(image, color)
+    color = color or iui.colors.white
+
+    local bx, by, bw, bh = iui.layout.getBounds()
+    local iw, ih = iui.graphics.getImageDimensions(image)
+
+    local mode = iui.style["imageMode"] or "aspectFit" --- @type IUIImageMode
+    local clip = iui.style["imageClip"] or false       --- @type boolean
+
+    local ox, oy, ow, oh = iui.utils.fill(mode, iw, ih, bx, by, bw, bh)
+
+    if clip then
+        iui.draw.pushClip(bx, by, bw, bh)
+    end
+
+    color:set()
+    iui.graphics.msdfImage(image, ox, oy, ow, oh)
+
+    if clip then
+        iui.draw.popClip()
+    end
+
+    iui.layout.advance()
+end

src/lovr/lib/iui/widgets/msdf-layered-image-9-slice.lua

@@ -0,0 +1,17 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+local parentPath = currentPath:match('(.-)[^%./]+%.$')
+
+--- @class IUILib
+local iui = require(parentPath .. "iui")
+
+--- @param image IUILayeredImage
+function iui.msdfLayeredImage9Slice(image)
+    local x, y, w, h = iui.layout.getBounds()
+
+    for _, item in ipairs(image) do
+        item.color:set()
+        iui.graphics.msdfNineSlice(item.image, x, y, w, h)
+    end
+
+    iui.layout.advance()
+end

src/lovr/lib/iui/widgets/msdf-layered-image.lua

@@ -0,0 +1,31 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+local parentPath = currentPath:match('(.-)[^%./]+%.$')
+
+--- @class IUILib
+local iui = require(parentPath .. "iui")
+
+--- @param image IUILayeredImage
+function iui.msdfLayeredImage(image)
+    local bx, by, bw, bh = iui.layout.getBounds()
+    local iw, ih = iui.graphics.getImageDimensions(image[1].image)
+
+    local mode = iui.style["imageMode"] or "aspectFit" --- @type IUIImageMode
+    local clip = iui.style["imageClip"] or false       --- @type boolean
+
+    local ox, oy, ow, oh = iui.utils.fill(mode, iw, ih, bx, by, bw, bh)
+
+    if clip then
+        iui.draw.pushClip(bx, by, bw, bh)
+    end
+
+    for _, item in ipairs(image) do
+        item.color:set()
+        iui.graphics.msdfImage(item.image, ox, oy, ow, oh)
+    end
+
+    if clip then
+        iui.draw.popClip()
+    end
+
+    iui.layout.advance()
+end

src/lovr/lib/iui/widgets/panel-background.lua

@@ -0,0 +1,14 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+local parentPath = currentPath:match('(.-)[^%./]+%.$')
+
+--- @class IUILib
+local iui = require(parentPath .. "iui")
+
+--- @param color? IUIColor
+function iui.panelBackground(color)
+    color = color or iui.colors.sysGray50
+    local x, y, w, h = iui.layout.getPanelBounds()
+
+    color:set()
+    iui.draw.panelBackground(x, y, w, h)
+end

src/lovr/lib/iui/widgets/progress.lua

@@ -0,0 +1,69 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+local parentPath = currentPath:match('(.-)[^%./]+%.$')
+
+--- @class IUILib
+local iui = require(parentPath .. "iui")
+
+local barHeight = 16
+
+--- @param value number The progress value.
+--- @param min? number The lower bound. Defaults to 0.
+--- @param max? number The upper bound. Defaults to 1.
+function iui.progress(value, min, max)
+    min = min or 0
+    max = max or 1
+
+    local _, intrinsicH = iui.layout.getWantsIntrinsic()
+
+    local disabled = iui.isDisabled()
+
+    local x, y, w, h = iui.layout.getBounds()
+    y = math.floor(y + (h - barHeight) * 0.5)
+    h = barHeight
+
+    local bx, by, bw, bh = x + 2, y + 2, w - 4, h - 4
+
+    if intrinsicH then
+        iui.layout.setIntrinsicHeight(barHeight)
+    end
+
+    -- Border
+    iui.colors.sysGray200:set()
+    iui.graphics.rectangle(x, y, w, h, 4, 4)
+
+    -- Background
+    if disabled then
+        iui.colors.sysGray100:set()
+    else
+        iui.colors.sysGray0:set()
+    end
+    iui.graphics.rectangle(x + 1, y + 1, w - 2, h - 2, 3, 3)
+
+    -- Bar
+    local shouldClip = value > min and value < max
+    if shouldClip then
+        local percent = (value - min) / (max - min)
+        percent = iui.utils.clamp(percent, 0, 1)
+
+        -- Force at least one full pixel and one empty pixel
+        local width = iui.utils.clamp(
+            iui.utils.round(bw * percent), 1, bw - 1
+        )
+        iui.graphics.clip(bx, by, width, bh)
+    end
+
+    if value > min then
+        if disabled then
+            iui.colors.sysGray200:set()
+        else
+            iui.colors.sysAccent500:set()
+        end
+        iui.graphics.rectangle(bx, by, bw, bh, 2, 2)
+    end
+
+    if shouldClip then
+        iui.graphics.clip()
+    end
+
+    iui.layout.advance()
+end

src/lovr/lib/iui/widgets/radio.lua

@@ -0,0 +1,114 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+local parentPath = currentPath:match('(.-)[^%./]+%.$')
+
+--- @class IUILib
+local iui = require(parentPath .. "iui")
+
+--- @generic T
+--- @param name string
+--- @param current T
+--- @param value T
+--- @return T
+function iui.radio(name, current, value)
+    local id = iui.beginID(name)
+
+    local intrinsicW, intrinsicH = iui.layout.getWantsIntrinsic()
+
+    local disabled = iui.isDisabled()
+
+    local font = iui.style["font"]
+    local padding = iui.style["padding"]
+
+    local textH = math.ceil(font:getHeight())
+    local size = textH + 2
+    local textX = size + padding
+
+    if intrinsicW then
+        local textW = math.ceil(font:getWidth(name))
+        iui.layout.setIntrinsicWidth(textX + textW)
+    end
+
+    if intrinsicH then
+        iui.layout.setIntrinsicHeight(size)
+    end
+
+    if iui.layout.containsPoint() then
+        iui.becomeHover()
+    end
+
+    if iui.hoverID == id and iui.input.mouse.pressed:has(1) then
+        iui.becomeActive()
+        iui.becomeFocus()
+    end
+
+    if iui.activeID == id then
+        if not iui.input.mouse.down:has(1) then
+            if iui.hoverID == id then
+                current = value
+            end
+
+            iui.activeID = nil
+        end
+    end
+
+    if iui.isFocused(id) then
+        if iui.input.keyboard.pressed["space"] then
+            current = value
+        end
+    end
+
+    local x, y, _, h = iui.layout.getBounds()
+
+    local textY = y + iui.utils.round((h - textH) / 2)
+
+    local radius = math.ceil(size / 2)
+    local radioY = y + iui.utils.round((h - size) / 2)
+
+    -- Outline
+    if not disabled then
+        if iui.isFocused(id) and iui.idiom ~= "vr" then
+            iui.colors.sysAccent500:set()
+        elseif iui.hoverID == id then
+            iui.colors.sysGray300:set()
+        else
+            iui.colors.sysGray200:set()
+        end
+        iui.graphics.circle(x + radius, radioY + radius, radius)
+    end
+
+    -- Background
+    if (iui.hoverID == id and iui.activeID == id) or disabled then
+        iui.colors.sysGray100:set()
+    else
+        iui.colors.sysGray0:set()
+    end
+    iui.graphics.circle(x + radius, radioY + radius, radius - 1.5)
+
+    -- Check
+    if current == value then
+        if disabled then
+            iui.colors.sysGray200:set()
+        elseif iui.hoverID == id and iui.activeID == id then
+            iui.colors.sysGray200:set()
+        elseif iui.hoverID == id then
+            iui.colors.sysGray400:set()
+        else
+            iui.colors.sysGray300:set()
+        end
+
+        iui.graphics.circle(x + radius, radioY + radius, radius - 4)
+    end
+
+    -- Label
+    if disabled then
+        iui.colors.sysGray300:set()
+    else
+        iui.colors.sysGray900:set()
+    end
+    iui.graphics.setFont(font)
+    iui.graphics.print(name, x + textX, textY)
+
+    iui.endID()
+
+    return current
+end

src/lovr/lib/iui/widgets/scroll-bar.lua

@@ -0,0 +1,81 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+local parentPath = currentPath:match('(.-)[^%./]+%.$')
+
+--- @class IUILib
+local iui = require(parentPath .. "iui")
+
+--- @alias IUIScrollBarDirection "horiz" | "vert"
+
+--- @param name string
+--- @param dir IUIScrollBarDirection
+--- @param value number
+--- @param length number
+--- @param min number
+--- @param max number
+--- @return number
+function iui.scrollBar(name, dir, value, length, min, max)
+    local id = iui.beginID(name, false)
+    local state = iui.state(id)
+
+    local x, y, w, h = iui.layout.getBounds()
+    local mx = iui.input.mouse.x
+    local my = iui.input.mouse.y
+
+    local pixelToValue = (max - min) / h
+    local mousePos = (my - y) * pixelToValue
+
+    local isScrollable = length < (max - min)
+
+    if isScrollable then
+        if iui.layout.containsPoint() then
+            iui.becomeHover()
+        end
+
+        if iui.hoverID == id and iui.input.mouse.pressed:has(1) then
+            iui.becomeActive()
+
+            if (mousePos < value) or (mousePos >= (value + length)) then
+                state.offset = length / 2
+            else
+                state.offset = mousePos - value
+            end
+        end
+    end
+
+    if iui.activeID == id then
+        value = math.min(math.max(mousePos - state.offset, min), max - length)
+
+        if not iui.input.mouse.down:has(1) then
+            iui.activeID = nil
+        end
+    end
+
+    if isScrollable then
+        iui.colors.sysGray0:set()
+        iui.graphics.rectangle(x, y, w, h)
+
+        local bx, by = x, y + (value / (max - min)) * h
+        local bw, bh = w, (length / (max - min)) * h
+        local by2 = by + bh
+        by = iui.utils.round(by)
+        bh = iui.utils.round(by2) - by
+
+        if iui.hoverID == id or iui.activeID == id then
+            iui.colors.sysGray200:set()
+        else
+            iui.colors.sysGray100:set()
+        end
+        iui.graphics.rectangle(bx, by, bw, bh)
+
+        iui.colors.sysGray200:set()
+        iui.graphics.rectangle(bx, by - 1, bw, 1)
+        iui.graphics.rectangle(bx, by + bh, bw, 1)
+    else
+        iui.colors.sysGray50:set()
+        iui.graphics.rectangle(x, y, w, h)
+    end
+
+    iui.endID()
+
+    return value
+end

src/lovr/lib/iui/widgets/scroll-view.lua

@@ -0,0 +1,272 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+local parentPath = currentPath:match('(.-)[^%./]+%.$')
+
+--- @class IUILib
+local iui = require(parentPath .. "iui")
+
+--- @class (exact) IUIScrollViewState
+--- @field manager? IUIScrollManager
+--- @field vy? number
+--- @field dragOrigin? { x: number, y: number }
+--- @field isDragging? boolean
+
+--- @class (exact) IUIScrollViewStackItem
+--- @field state IUIScrollViewState
+--- @field manager IUIScrollManager
+--- @field id number
+--- @field innerX number
+--- @field innerY number
+--- @field innerW number
+--- @field innerH number
+--- @field containsMouse boolean
+--- @field disabled boolean
+
+--- @type IUIScrollViewStackItem[]
+local scrollStack = {}
+
+--- @class IUIScrollManager
+--- @field x number
+--- @field y number
+--- @field contentWidth number
+--- @field contentHeight number
+--- @field clipWidth number
+--- @field clipHeight number
+--- @field shouldInterruptAnimation boolean
+--- @field beganDragging? fun(self: IUIScrollManager)
+local ScrollManager = {}
+ScrollManager.__index = ScrollManager
+
+function ScrollManager:fixOffset()
+    self.x = math.max(math.min(self.x, self.contentWidth - self.clipWidth), 0)
+    self.y = math.max(math.min(self.y, self.contentHeight - self.clipHeight), 0)
+end
+
+--- @param x number
+--- @param y number
+--- @param w? number
+--- @param h? number
+function ScrollManager:scrollTo(x, y, w, h)
+    local minX = self.x
+    local maxX = self.x + self.clipWidth
+    local targetMinX = x
+    local targetMaxX = x + (w or 1)
+
+    local minY = self.y
+    local maxY = self.y + self.clipHeight
+    local targetMinY = y
+    local targetMaxY = y + (h or 1)
+
+    if targetMaxX > maxX then
+        maxX = targetMaxX
+        minX = maxX - self.clipWidth
+    end
+
+    if targetMinX < minX then
+        minX = targetMinX
+        maxX = minX + self.clipWidth
+    end
+
+    if targetMaxY > maxY then
+        maxY = targetMaxY
+        minY = maxY - self.clipHeight
+    end
+
+    if targetMinY < minY then
+        minY = targetMinY
+        maxY = minY + self.clipHeight
+    end
+
+    self.x = minX
+    self.y = minY
+    self.shouldInterruptAnimation = true
+
+    self:fixOffset()
+end
+
+iui.ScrollManager = ScrollManager
+
+--- @return IUIScrollManager
+function iui.newScrollManager()
+    --- @type IUIScrollManager
+    local out = setmetatable({}, ScrollManager)
+
+    out.x = 0
+    out.y = 0
+    out.contentWidth = 0
+    out.contentHeight = 0
+    out.clipWidth = 0
+    out.clipHeight = 0
+    out.shouldInterruptAnimation = false
+
+    return out
+end
+
+--- @param name string
+--- @param manager? IUIScrollManager
+function iui.scrollView(name, manager)
+    local id = iui.beginID(name, false)
+
+    --- @type IUIScrollViewState
+    local state = iui.state(id)
+
+    if not manager then
+        manager = state.manager
+
+        if not manager then
+            manager = iui.newScrollManager()
+            state.manager = manager
+        end
+    end
+
+    local x, y, w, h = iui.layout.getBounds()
+    local containsMouse = iui.layout.containsPoint()
+    local disabled = iui.isDisabled()
+
+    local scrollSize = iui.style["scrollSize"]
+
+    local innerX, innerY = x + 1, y + 1
+    local innerW, innerH = w - (3 + scrollSize), h - 2
+
+    iui.colors.sysGray200:set()
+    iui.graphics.rectangle(x, y, w, h)
+
+    iui.colors.sysGray0:set()
+    iui.graphics.rectangle(innerX, innerY, innerW, innerH)
+
+    iui.layout.beginZStack()
+    iui.draw.pushClip(innerX, innerY, innerW, innerH)
+    local panel = iui.layout.beginPanel(innerX, innerY, innerW, innerH)
+    panel.rowY = panel.rowY - iui.utils.round(manager.y)
+
+    --- @type IUIScrollViewStackItem
+    local stackItem = iui.pool.get("scroll_view_stack_item")
+
+    stackItem.state = state
+    stackItem.manager = manager
+    stackItem.id = id
+    stackItem.innerX = innerX
+    stackItem.innerY = innerY
+    stackItem.innerW = innerW
+    stackItem.innerH = innerH
+    stackItem.containsMouse = containsMouse
+    stackItem.disabled = disabled
+
+    table.insert(scrollStack, stackItem)
+end
+
+function iui.endScrollView()
+    --- @type IUIScrollViewStackItem
+    local stackItem = table.remove(scrollStack)
+
+    local scrollSize = iui.style["scrollSize"]
+
+    local state = stackItem.state
+    local manager = stackItem.manager
+    local id = stackItem.id
+    local innerX = stackItem.innerX
+    local innerY = stackItem.innerY
+    local innerW = stackItem.innerW
+    local innerH = stackItem.innerH
+    local containsMouse = stackItem.containsMouse
+    local disabled = stackItem.disabled
+
+    local scrollX, scrollY = innerX + innerW + 1, innerY
+    local scrollW, scrollH = scrollSize, innerH
+
+    local cw, ch = iui.layout.getContentSize()
+    cw, ch = cw + manager.x, ch + iui.utils.round(manager.y)
+    iui.layout.endPanel()
+    iui.draw.popClip()
+
+    iui.layout.beginPanel(scrollX, scrollY, scrollW, scrollH, 0)
+    iui.layout.fillPanel()
+    manager.y = iui.scrollBar("scroll", "vert", manager.y, innerH, 0, ch)
+    iui.layout.endPanel()
+    iui.layout.endZStack()
+
+    if manager.shouldInterruptAnimation then
+        manager.shouldInterruptAnimation = false
+        state.vy = 0
+    end
+
+    if state.vy ~= nil and state.vy ~= 0 then
+        manager.y = manager.y + state.vy * iui.dt
+        state.vy = state.vy * math.exp(-4 * iui.dt)
+        if math.abs(state.vy) * iui.dt < 0.05 then
+            state.vy = 0
+        end
+    end
+
+    local mx, my = iui.input.mouse.x, iui.input.mouse.y
+
+    if not disabled then
+        if containsMouse then
+            local scrollIncrement = iui.input.mouse.scrollY * 21
+            if iui.input.keyboard.down:has("lalt") then
+                scrollIncrement = scrollIncrement * 5
+            end
+            manager.y = manager.y - scrollIncrement
+
+            -- Set up a potential drag event
+            if iui.input.mouse.pressed:has(1) then
+                -- Terminate any scrolling
+                state.vy = 0
+
+                -- The mouse must not be in the scrollbar
+                local isOutsideScroll = false
+                isOutsideScroll = isOutsideScroll or mx < scrollX
+                isOutsideScroll = isOutsideScroll or mx >= scrollX + scrollW
+                isOutsideScroll = isOutsideScroll or my < scrollY
+                isOutsideScroll = isOutsideScroll or my >= scrollY + scrollH
+
+                local canScroll = ch > innerH
+                canScroll = canScroll and iui.idiom == "vr"
+                if isOutsideScroll and canScroll then
+                    state.dragOrigin = { x = mx, y = my }
+                end
+            end
+        end
+
+        if state.dragOrigin then
+            if not iui.input.mouse.down:has(1) then
+                state.dragOrigin = nil
+            else
+                -- local dx = mx - state.dragOrigin.x
+                local dy = my - state.dragOrigin.y
+                if math.abs(dy) > 15 then
+                    state.dragOrigin = nil
+                    state.isDragging = true
+                    if manager.beganDragging then
+                        manager:beganDragging()
+                    end
+                    iui.becomeActive(id)
+                end
+            end
+        end
+
+        if state.isDragging then
+            if not iui.input.mouse.down:has(1) then
+                state.isDragging = false
+                iui.activeID = nil
+                -- state.vy = -iui.input.mouse.dy / iui.dt
+                _, state.vy = iui.input.mouse.getVelocity()
+                if math.abs(state.vy) > 2000 then
+                    state.vy = iui.utils.sign(state.vy) * 2000
+                end
+            else
+                manager.y = manager.y - iui.input.mouse.dy
+            end
+        end
+    end
+
+    manager.clipWidth = innerW
+    manager.clipHeight = innerH
+    manager.contentWidth = cw
+    manager.contentHeight = ch
+
+    manager:fixOffset()
+
+    iui.endID()
+
+    iui.pool.put(stackItem)
+end

src/lovr/lib/iui/widgets/slider.lua

@@ -0,0 +1,109 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+local parentPath = currentPath:match('(.-)[^%./]+%.$')
+
+--- @class IUILib
+local iui = require(parentPath .. "iui")
+
+local radius = 8
+
+--- @param name string
+--- @param value number
+--- @param min number
+--- @param max number
+--- @return number
+function iui.slider(name, value, min, max)
+    local id = iui.beginID(name)
+
+    local _, intrinsicH = iui.layout.getWantsIntrinsic()
+
+    local disabled = iui.isDisabled()
+
+    local x, y, w, h = iui.layout.getBounds()
+    local percent = (value - min) / (max - min)
+    local thumb = x + radius + iui.utils.round((w - radius * 2) * percent)
+
+    if intrinsicH then
+        iui.layout.setIntrinsicHeight(radius * 2)
+    end
+
+    if iui.layout.containsPoint() then
+        iui.becomeHover()
+    end
+
+    if iui.hoverID == id and iui.input.mouse.pressed:has(1) then
+        iui.becomeActive()
+        iui.becomeFocus()
+    end
+
+    if iui.activeID == id then
+        local mousePercent = (iui.input.mouse.x - x - radius) / (w - radius * 2)
+        mousePercent = math.max(math.min(1, mousePercent), 0)
+
+        value = min + mousePercent * (max - min)
+
+        if not iui.input.mouse.down:has(1) then
+            iui.activeID = nil
+        end
+    end
+
+    if iui.isFocused(id) and iui.activeID ~= id then
+        local increment = (max - min) / 10
+        local base = iui.utils.round((value - min) / increment)
+        if iui.input.keyboard.pressed["left"] then
+            value = math.max(min, min + (base - 1) * increment)
+        elseif iui.input.keyboard.pressed["right"] then
+            value = math.min(max, min + (base + 1) * increment)
+        end
+    end
+
+    percent = (value - min) / (max - min)
+    thumb = x + radius + iui.utils.round((w - radius * 2) * percent)
+
+    -- Track
+    if disabled then
+        iui.colors.sysGray100:set()
+    else
+        iui.colors.sysGray200:set()
+    end
+    iui.graphics.rectangle(
+        x + radius, y + iui.utils.round(h / 2) - 2,
+        w - radius * 2, 4,
+        2, 2
+    )
+
+    iui.colors.sysGray50:set()
+    iui.graphics.rectangle(
+        x + radius + 1, y + iui.utils.round(h / 2) - 1,
+        w - radius * 2 - 2, 2,
+        1, 1
+    )
+
+    -- Thumb
+    if disabled then
+        iui.colors.sysGray100:set()
+    elseif iui.isFocused(id) and iui.idiom ~= "vr" then
+        iui.colors.sysAccent500:set()
+    elseif iui.activeID == id then
+        iui.colors.sysGray200:set()
+    elseif iui.hoverID == id then
+        iui.colors.sysGray400:set()
+    else
+        iui.colors.sysGray300:set()
+    end
+    iui.graphics.circle(thumb, y + iui.utils.round(h / 2), radius)
+
+    if not disabled then
+        if iui.activeID == id then
+            iui.colors.sysGray50:set()
+        elseif iui.hoverID == id then
+            iui.colors.sysGray200:set()
+        else
+            iui.colors.sysGray100:set()
+        end
+        iui.graphics.circle(thumb, y + iui.utils.round(h / 2), radius - 1.5)
+    end
+
+    iui.endID()
+
+    return value
+end

src/lovr/lib/iui/widgets/split-view.lua

@@ -0,0 +1,167 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+local parentPath = currentPath:match('(.-)[^%./]+%.$')
+
+--- @class IUILib
+local iui = require(parentPath .. "iui")
+
+--- @alias IUISplitViewDirection "horiz" | "vert"
+--- @alias IUISplitViewSide "min" | "max"
+
+--- @class (exact) IUISplitStackItem
+--- @field direction IUISplitViewDirection
+--- @field current number
+--- @field x number
+--- @field y number
+--- @field w number
+--- @field h number
+
+--- @type IUISplitStackItem[]
+local splitStack = {}
+
+--- @param name string
+--- @param direction IUISplitViewDirection
+--- @param current number
+--- @return number
+function iui.splitView(name, direction, current)
+    local id = iui.beginID(name, false)
+    local state = iui.state(id)
+
+    local x, y, w, h = iui.layout.getPanelBounds()
+
+    local mx = iui.input.mouse.x
+    local my = iui.input.mouse.y
+    local spacing = iui.style["spacing"]
+    local splitMinEdge = iui.style["splitMinEdge"] or 8
+    local splitMaxEdge = iui.style["splitMaxEdge"] or 8
+    local splitSide = iui.style["splitSide"] or "min" --- @type IUISplitViewSide
+
+    if splitSide == "max" then
+        current = w - current
+    end
+
+    local handleWidth = math.ceil(spacing * 0.75)
+    local handleMin = current - handleWidth
+    local handleMax = current + handleWidth + 1
+
+    if direction == "horiz" then
+        if mx >= x + handleMin and mx <= x + handleMax then
+            if my >= y and my < y + h then
+                iui.becomeHover()
+            end
+        end
+
+        if iui.hoverID == id then
+            if iui.input.mouse.pressed:has(1) then
+                iui.becomeActive()
+                state.offset = (mx - x) - current
+            end
+        end
+
+        if iui.activeID == id then
+            current = (mx - x) - state.offset
+
+            if not iui.input.mouse.down:has(1) then
+                iui.activeID = nil
+            end
+        end
+
+        if iui.hoverID == id or iui.activeID == id then
+            iui.cursor = "sizewe"
+        end
+    elseif direction == "vert" then
+        if my >= y + handleMin and my <= y + handleMax then
+            if mx >= x and mx < x + w then
+                iui.becomeHover()
+            end
+        end
+
+        if iui.hoverID == id then
+            if iui.input.mouse.pressed:has(1) then
+                iui.becomeActive()
+                state.offset = (mx - x) - current
+            end
+        end
+
+        if iui.activeID == id then
+            current = (my - y) - state.offset
+
+            if not iui.input.mouse.down:has(1) then
+                iui.activeID = nil
+            end
+        end
+
+        if iui.hoverID == id or iui.activeID == id then
+            iui.cursor = "sizens"
+        end
+    end
+
+    current = iui.utils.round(current)
+
+    if current < splitMinEdge then
+        current = splitMinEdge
+    end
+
+    if direction == "horiz" then
+        if current > w - (splitMaxEdge + 1) then
+            current = w - (splitMaxEdge + 1)
+        end
+    elseif direction == "vert" then
+        if current > h - (splitMaxEdge + 1) then
+            current = h - (splitMaxEdge + 1)
+        end
+    end
+
+    iui.panelBackground()
+
+    local pos = current
+    iui.colors.sysGray0:set()
+    if direction == "horiz" then
+        iui.graphics.rectangle(x + pos, y, 1, h)
+    elseif direction == "vert" then
+        iui.graphics.rectangle(x, y + pos, w, 1)
+    end
+
+    if direction == "horiz" then
+        iui.layout.beginPanel(x, y, current, h)
+    elseif direction == "vert" then
+        iui.layout.beginPanel(x, y, w, current)
+    end
+
+    --- @type IUISplitStackItem
+    local item = iui.pool.get("split_view_stack_item")
+    item.direction = direction
+    item.current = current
+    item.x, item.y, item.w, item.h = x, y, w, h
+
+    table.insert(splitStack, item)
+
+    if splitSide == "max" then
+        current = w - current
+    end
+
+    return current
+end
+
+function iui.splitViewDivider()
+    --- @type IUISplitStackItem
+    local item = table.remove(splitStack)
+    local direction = item.direction
+    local x, y, w, h = item.x, item.y, item.w, item.h
+    local current = item.current
+
+    iui.layout.endPanel()
+
+    if direction == "horiz" then
+        iui.layout.beginPanel(x + current + 1, y, w - (current + 1), h)
+    elseif direction == "vert" then
+        iui.layout.beginPanel(x, y + current + 1, w, h - (current + 1))
+    end
+
+    iui.pool.put(item)
+end
+
+function iui.endSplitView()
+    iui.layout.endPanel()
+
+    iui.endID()
+end

src/lovr/lib/iui/widgets/sub-menu.lua

@@ -0,0 +1,221 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+local parentPath = currentPath:match('(.-)[^%./]+%.$')
+
+--- @class IUILib
+local iui = require(parentPath .. "iui")
+
+--- @class IUISubMenuController
+--- @field isMenuBar boolean
+--- @field subMenuIDs number[]
+--- @field currentSubMenuIndex number
+--- @field hoveredSubMenuIndex? number
+--- @field panelClaimedMouseDown boolean
+--- @field beginSubMenu fun(): number?
+--- @field endSubMenu fun()
+--- @field setSubMenu fun(id: number)
+--- @field activate fun()
+--- @field deactivate fun()
+
+--- @class (exact) IUISubMenuStackItem
+--- @field state { panelW: number, panelH: number }
+
+--- @type IUISubMenuStackItem[]
+local subMenuStack = {}
+
+local disclosureImage
+
+--- @param name string
+--- @return boolean isOpen
+function iui.subMenu(name)
+    if disclosureImage == nil then
+        disclosureImage = iui.backend.system.getMSDFImage(
+            "assets/glyph-disclosure.png"
+        )
+    end
+
+    local id = iui.beginID(name, false)
+    local state = iui.state(id)
+
+    local intrinsicW, intrinsicH = iui.layout.getWantsIntrinsic()
+
+    local font = iui.style["font"]
+    local padding = iui.style["padding"]
+    local spacing = iui.style["menuItemSpacing"]
+
+    --- @type IUISubMenuController
+    local controller = iui.style["subMenuController"]
+    local isPanelSubMenu = iui.style["isPanelSubMenu"] or false
+
+    local textW = math.ceil(font:getWidth(name))
+    local textH = math.ceil(font:getHeight())
+    local discSize = textH - 2
+
+    if intrinsicW then
+        if isPanelSubMenu then
+            iui.layout.setIntrinsicWidth(
+                textW + padding * 2 + spacing + discSize
+            )
+        else
+            iui.layout.setIntrinsicWidth(textW + padding * 2)
+        end
+    end
+
+    if intrinsicH then
+        iui.layout.setIntrinsicHeight(textH + padding * 2)
+    end
+
+    if iui.layout.containsPoint() then
+        iui.becomeHover()
+    end
+
+    local isShowingPanel = false
+    local subMenuID = controller.beginSubMenu()
+    if subMenuID == id then
+        if iui.hoverID == id and iui.input.mouse.pressed:has(1) then
+            if not isPanelSubMenu then
+                controller.deactivate()
+            else
+                isShowingPanel = true
+            end
+            iui.input.mouse.pressed:remove(1)
+        else
+            isShowingPanel = true
+        end
+    end
+
+    if iui.hoverID == id then
+        local clicked = false
+        if iui.input.mouse.pressed:has(1) then
+            if not isPanelSubMenu then
+                controller.activate()
+            end
+            iui.input.mouse.pressed:remove(1)
+            clicked = true
+        end
+
+        state.hoverTime = (state.hoverTime or 0) + iui.dt
+
+        if state.hoverTime > 0.2 or clicked or not isPanelSubMenu then
+            controller.setSubMenu(id)
+        end
+
+        if (controller.hoveredSubMenuIndex or 0) < controller.currentSubMenuIndex - 1 then
+            controller.hoveredSubMenuIndex = controller.currentSubMenuIndex - 1
+        end
+    else
+        state.hoverTime = nil
+    end
+
+    local x, y, w, h = iui.layout.getBounds()
+
+    -- Background
+    if isPanelSubMenu then
+        if iui.hoverID == id or subMenuID == id then
+            iui.colors.sysGray200:set()
+            iui.graphics.rectangle(x + 4, y, w - 8, h, 2, 2)
+        end
+    else
+        if iui.hoverID == id or subMenuID == id then
+            iui.colors.sysGray200:set()
+            iui.graphics.rectangle(x, y + 2, w, h - 4, 2, 2)
+        end
+    end
+
+    iui.colors.sysGray900:set()
+    iui.graphics.setFont(font)
+    local textX
+    local textY = y + iui.utils.round((h - textH) / 2)
+    if isPanelSubMenu then
+        textX = x + padding
+        local discY = y + iui.utils.round((h - discSize) / 2)
+        iui.graphics.msdfImage(
+            disclosureImage, x + w - padding - discSize, discY, discSize, discSize
+        )
+    else
+        textX = x + iui.utils.round((w - textW) / 2)
+    end
+    iui.graphics.print(name, textX, textY)
+
+    iui.endID()
+
+    if isShowingPanel then
+        local panelX, panelY
+        if isPanelSubMenu then
+            panelX = x + w
+            panelY = y - 5
+        else
+            panelX = x
+            panelY = y + h - 2
+        end
+        local panelW = state.panelW or 200
+        local panelH = state.panelH or 400
+
+        local mx, my = iui.input.mouse.x, iui.input.mouse.y
+        if mx >= panelX and my >= panelY and mx < panelX + panelW and my < panelY + panelH then
+            if iui.input.mouse.pressed:has(1) then
+                controller.panelClaimedMouseDown = true
+            end
+
+            if (controller.hoveredSubMenuIndex or 0) < controller.currentSubMenuIndex - 1 then
+                controller.hoveredSubMenuIndex = controller.currentSubMenuIndex - 1
+            end
+        end
+
+        if state.panelH == nil then
+            iui.draw.beginHiding()
+        end
+
+        -- Panel background
+        iui.colors.sysGray300:set()
+        iui.graphics.rectangle(panelX, panelY, panelW, state.panelH or 0, 4, 4)
+
+        iui.colors.sysGray100:set()
+        iui.graphics.rectangle(panelX + 1, panelY + 1, panelW - 2, (state.panelH or 0) - 2, 3, 3)
+
+        iui.layout.beginPanel(panelX, panelY, panelW, panelH, 1)
+        iui.style.push()
+        iui.style["subMenuController"] = controller
+        iui.style["isPanelSubMenu"] = true
+        iui.layout.beginDynamicRow(1, 4)
+        iui.layout.spacer()
+
+        if state.panelW then
+            iui.layout.beginDynamicRow()
+        else
+            iui.layout.beginIntrinsicRow(10, 1)
+        end
+
+        --- @type IUISubMenuStackItem
+        local stackItem = iui.pool.get("sub_menu_stack_item")
+        stackItem.state = state
+        table.insert(subMenuStack, stackItem)
+    else
+        controller.endSubMenu()
+    end
+
+    return isShowingPanel
+end
+
+function iui.endSubMenu()
+    --- @type IUISubMenuStackItem
+    local stackItem = table.remove(subMenuStack)
+
+    local state = stackItem.state
+
+    iui.pool.put(stackItem)
+
+    if state.panelH == nil then
+        iui.draw.endHiding()
+    end
+
+    state.panelW, state.panelH = iui.layout.getContentSize()
+    state.panelW = math.max(state.panelW, 100)
+    state.panelH = state.panelH + 4
+
+    --- @type IUISubMenuController
+    local controller = iui.style["subMenuController"]
+    controller.endSubMenu()
+
+    iui.style.pop()
+    iui.layout.endPanel(false)
+end

src/lovr/lib/iui/widgets/tab-bar.lua

@@ -0,0 +1,149 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+local parentPath = currentPath:match('(.-)[^%./]+%.$')
+
+--- @class IUILib
+local iui = require(parentPath .. "iui")
+
+--- @class IUITabBarStackItem
+--- @field barHeight number
+--- @field x number
+--- @field y number
+--- @field w number
+--- @field h number
+
+--- @type IUITabBarStackItem[]
+local itemStack = {}
+
+function iui.tabBar()
+    local x, y, w, h = iui.layout.getPanelBounds()
+
+    local barHeight = iui.layout.getDefaultRowHeight() + 1
+
+    iui.colors.sysGray100:set()
+    iui.draw.panelBackground(x, y, w, barHeight - 1)
+
+    iui.colors.sysGray200:set()
+    iui.graphics.rectangle(x, y + barHeight - 1, w, 1)
+
+    iui.layout.beginPanel(x + 1, y, w - 2, barHeight, 0)
+    iui.layout.beginIntrinsicRow(nil, nil, barHeight)
+    iui.style.push()
+    iui.style["spacing"] = 0
+
+    --- @type IUITabBarStackItem
+    local item = iui.pool.get("tab_bar_stack_item")
+    item.barHeight = barHeight
+    item.x, item.y, item.w, item.h = x, y, w, h
+    table.insert(itemStack, item)
+end
+
+function iui.tabBarDivider()
+    --- @type IUITabBarStackItem
+    local item = table.remove(itemStack)
+    local barHeight = item.barHeight
+    local x, y, w, h = item.x, item.y, item.w, item.h
+    iui.pool.put(item)
+
+    iui.style.pop()
+    iui.layout.endPanel()
+
+    iui.layout.beginPanel(x, y + barHeight, w, h - barHeight)
+end
+
+function iui.endTabBar()
+    iui.layout.endPanel()
+end
+
+--- @generic T
+--- @param name string
+--- @param current T
+--- @param value T
+--- @return T
+function iui.tabItem(name, current, value)
+    local id = iui.beginID(name)
+    local out = current
+
+    local intrinsicW, intrinsicH = iui.layout.getWantsIntrinsic()
+
+    local font = iui.style["font"]
+    local padding = iui.style["padding"]
+
+    local textH = math.ceil(font:getHeight())
+    local size = textH + 2
+
+    if intrinsicW then
+        local textW = math.ceil(font:getWidth(name))
+        iui.layout.setIntrinsicWidth(textW + padding * 4)
+    end
+
+    if intrinsicH then
+        iui.layout.setIntrinsicHeight(size)
+    end
+
+    if iui.layout.containsPoint() then
+        iui.becomeHover()
+    end
+
+    if iui.hoverID == id and iui.input.mouse.pressed:has(1) then
+        out = value
+        iui.becomeFocus()
+    end
+
+    if iui.isFocused(id) then
+        if iui.input.keyboard.pressed["space"] then
+            out = value
+        end
+    end
+
+    local x, y, w, h = iui.layout.getBounds()
+
+    local textX = x + padding * 2
+    local textY = y + iui.utils.round((h - textH) / 2)
+
+    local top = y + 1
+    local fh = h - 9
+
+    --- @type IUIColor
+    local backgroundColor
+
+    if out == value then
+        iui.graphics.clip(x, y, w + 1, h)
+        backgroundColor = iui.colors.sysGray50
+        textY = textY
+        fh = fh + 2
+    else
+        iui.graphics.clip(x, y, w + 1, h - 1)
+        top = top + 2
+        textY = textY + 1
+
+        if iui.hoverID == id then
+            backgroundColor = iui.colors.sysGray200
+        else
+            backgroundColor = iui.colors.sysGray100
+        end
+    end
+
+    -- Outline
+    iui.colors.sysGray200:set()
+    iui.graphics.rectangle(x, top, w + 1, h + 6, 6, 6)
+
+    -- Background
+    backgroundColor:set()
+    iui.graphics.rectangle(x + 1, top + 1, w - 1, h + 5, 5, 5)
+
+    if iui.idiom ~= "vr" and iui.isFocused(id) then
+        iui.colors.sysAccent500:set()
+        iui.graphics.rectangle(x + padding, y + h - 6, w - padding * 2, 2, 1, 1)
+    end
+
+    -- Label
+    iui.colors.sysGray900:set()
+    iui.graphics.setFont(font)
+    iui.graphics.print(name, textX, textY)
+
+    iui.graphics.clip()
+
+    iui.endID()
+
+    return out
+end

src/lovr/lib/iui/widgets/text-field.lua

@@ -0,0 +1,111 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+local parentPath = currentPath:match('(.-)[^%./]+%.$')
+
+--- @class IUILib
+local iui = require(parentPath .. "iui")
+
+local utf8 = require "utf8"
+
+--- @param name string
+--- @param s string
+--- @return string
+function iui.textField(name, s)
+    local id = iui.beginID(name)
+
+    local state = iui.state(id)
+
+    local x, y, w, h = iui.layout.getBounds()
+
+    local disabled = iui.isDisabled()
+
+    local font = iui.style["font"]
+    local padding = iui.style["padding"]
+
+    if iui.layout.containsPoint() then
+        iui.becomeHover()
+    end
+
+    if iui.hoverID == id then
+        iui.cursor = "ibeam"
+
+        if iui.input.mouse.pressed:has(1) then
+            iui.becomeFocus()
+        end
+    end
+
+    if iui.isFocused(id) then
+        state.time = (state.time or 0) + iui.dt
+        if state.showCursor == nil then
+            state.showCursor = true
+        end
+
+        while state.time > 0.5 do
+            state.showCursor = not state.showCursor
+            state.time = state.time - 0.5
+        end
+
+        local changedBuffer = false
+
+        if iui.input.textBuffer ~= nil then
+            s = s .. iui.input.textBuffer
+            iui.input.textBuffer = nil
+
+            changedBuffer = true
+        end
+
+        if iui.input.keyboard.pressed["backspace"] then
+            local idx = utf8.offset(s, -1)
+            if idx then
+                s = string.sub(s, 1, idx - 1)
+
+                changedBuffer = true
+            end
+        end
+
+        if changedBuffer then
+            state.showCursor = true
+            state.time = 0
+        end
+    else
+        state.time = nil
+        state.showCursor = nil
+    end
+
+    -- Outline
+    if iui.isFocused(id) then
+        iui.colors.sysAccent500:set()
+    elseif iui.hoverID == id then
+        iui.colors.sysGray300:set()
+    else
+        iui.colors.sysGray200:set()
+    end
+    iui.graphics.rectangle(x, y, w, h, 8, 8)
+
+    -- Background
+    if disabled then
+        iui.colors.sysGray100:set()
+    else
+        iui.colors.sysGray0:set()
+    end
+    iui.graphics.rectangle(x + 1, y + 1, w - 2, h - 2, 7, 7)
+
+    if disabled then
+        iui.colors.sysGray300:set()
+    else
+        iui.colors.sysGray900:set()
+    end
+    iui.graphics.setFont(font)
+    local textW, textH = font:getWidth(s), font:getHeight()
+    local textY = y + iui.utils.round((h - textH) / 2)
+    iui.graphics.print(s, x + padding, textY)
+
+    if iui.isFocused(id) and state.showCursor then
+        iui.colors.sysAccent500:set()
+        local radius = (iui.detail == "high" and 1 or nil)
+        iui.graphics.rectangle(x + padding + textW, textY, 2, textH, radius, radius)
+    end
+
+    iui.endID()
+
+    return s
+end

src/lovr/lib/iui/window-manager.lua

@@ -0,0 +1,64 @@
+local currentPath = (...):match('(.-)[^%./]+$')
+
+--- @class IUILib
+local iui = require(currentPath .. "iui")
+
+--- @class IUIWindowManager
+--- @field draw IUIDrawRootContext
+--- @field layer IUILayerRootContext
+--- @field state IUIStateRootContext
+--- @field disabledCount number
+--- @field hoverID? number The ID of the widget a pointer is hovering over.
+--- @field activeID? number The ID of the widget that's being actively used.
+--- @field cursor? IUICursorName The desired mouse cursor to display.
+--- @field hadActiveID boolean Internal flag for detecting widget deactivation.
+local IUIWindowManager = {}
+IUIWindowManager.__index = IUIWindowManager
+
+--- @return IUIWindowManager
+function iui.newWindowManager()
+    --- @type IUIWindowManager
+    local manager = {
+        draw = iui.draw.newRootContext(),
+        layer = iui.layer.newRootContext(),
+        state = iui.state.newRootContext(),
+        disabledCount = 0,
+        hadActiveID = false,
+    }
+    setmetatable(manager, IUIWindowManager)
+
+    return manager
+end
+
+function IUIWindowManager:beginFrame()
+    iui.disabledCount = 0
+    iui.hoverID = nil
+    iui.cursor = nil
+
+    iui.resetIDCheck()
+    iui.state.beginFrame()
+    iui.draw.beginFrame()
+    iui.layout.beginFrame()
+    iui.style.beginFrame()
+    iui.layer.beginFrame()
+end
+
+function IUIWindowManager:endFrame()
+    if iui.disabledCount ~= 0 then
+        error("Unbalanced control disable count")
+    end
+
+    if self.activeID == nil and self.hadActiveID == true then
+        self.hadActiveID = false
+
+        if iui.widgetDeactivated then
+            iui.widgetDeactivated()
+        end
+    end
+
+    iui.layout.endFrame()
+    iui.draw.endFrame()
+    iui.layer.endFrame()
+    iui.style.endFrame()
+    iui.state.endFrame()
+end

src/lovr/lib/lovr-iui/.gitignore

@@ -0,0 +1,2 @@
+.DS_Store
+.vscode

src/lovr/lib/lovr-iui/LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2026 Donald Hays
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

src/lovr/lib/lovr-iui/README.md

@@ -0,0 +1,136 @@
+# LÖVR-IUI
+
+A LÖVR backend for the [IUI](https://github.com/DonaldHays/iui) immediate mode
+GUI library.
+
+A [sample project](https://github.com/DonaldHays/iui-sample-lovr) that uses this
+backend is available.
+
+## Installation
+
+This library provides the backend for [IUI](https://github.com/DonaldHays/iui)
+for use in LÖVR projects. Both `iui` and `lovr-iui` must be added to your LÖVR
+project.
+
+If you are using the desktop idiom, you must also include the
+[lovr-mouse](https://github.com/bjornbytes/lovr-mouse) library in your project.
+
+## Minimal Desktop Sample
+
+### conf.lua
+```lua
+function lovr.conf(t)
+    t.modules.headset = nil
+end
+```
+
+### main.lua
+```lua
+local iui = require "iui"
+local backend = require "lovr-iui"
+local mouse = require "lovr-mouse"
+
+local labelText = "Click the button!"
+
+function lovr.load()
+    backend.mouse = mouse
+
+    iui.load(backend)
+end
+
+function lovr.update(dt)
+    iui.beginFrame(dt)
+    iui.beginWindow(lovr.system.getWindowDimensions())
+
+    iui.panelBackground()
+    iui.label(labelText)
+    if iui.button("Say Hello") then
+        labelText = "Hello, World!"
+    end
+
+    iui.endWindow()
+    iui.endFrame()
+end
+
+function lovr.draw(pass)
+    backend.graphics.pass = pass
+
+    iui.draw()
+end
+
+function lovr.mousemoved(x, y, dx, dy)
+    backend.mousemoved(x, y, dx, dy)
+end
+
+function lovr.mousepressed(x, y, button)
+    backend.mousepressed(x, y, button)
+end
+
+function lovr.mousereleased(x, y, button)
+    backend.mousereleased(x, y, button)
+end
+
+function lovr.wheelmoved(x, y)
+    backend.wheelmoved(x, y)
+end
+
+function lovr.keypressed(key, scancode, isRepeat)
+    backend.keypressed(key, scancode, isRepeat)
+end
+
+function lovr.keyreleased(key, scancode)
+    backend.keyreleased(key, scancode)
+end
+
+function lovr.textinput(text)
+    backend.textinput(text)
+end
+```
+
+## Minimal VR Sample
+
+### conf.lua
+```lua
+function lovr.conf(t)
+    t.headset.supersample = 2
+end
+```
+
+### main.lua
+```lua
+local iui = require "iui"
+local backend = require "lovr-iui"
+
+--- @type LovrIUIWorldWindow
+local window
+
+local labelText = "Click the button!"
+
+function lovr.load()
+    iui.load(backend)
+
+    window = backend.worldWindow.new()
+end
+
+function lovr.update(dt)
+    iui.beginFrame(dt)
+
+    if window:beginFrame() then
+        iui.beginWindow(window.w, window.h)
+        iui.panelBackground()
+        iui.label(labelText)
+        if iui.button("Say Hello") then
+            labelText = "Hello, World!"
+        end
+        iui.endWindow()
+
+        window:endFrame()
+    end
+
+    iui.endFrame()
+end
+
+function lovr.draw(pass)
+    window:draw(pass)
+end
+```

src/lovr/lib/lovr-iui/graphics.lua

@@ -0,0 +1,400 @@
+local iui                           --- @type IUILib
+
+local colorClipShader               --- @type Shader
+local fontClipShader                --- @type Shader
+local imageClipShader               --- @type Shader
+local imageUnclippedShader          --- @type Shader
+local msdfImageClipShader           --- @type Shader
+local msdfImageUnclippedShader      --- @type Shader
+
+local nearestImageSampler           --- @type Sampler
+local linearImageSampler            --- @type Sampler
+
+local currentImageFilter = "linear" --- @type IUIImageFilter
+local currentShader = nil           --- @type Shader?
+local isFilterDirty = false         --- @type boolean
+local isClipDirty = false           --- @type boolean
+local currentClip = nil             --- @type number[]?
+
+local currentWindow                 --- @type LovrIUIWorldWindow
+local windowWidth                   --- @type number
+local windowHeight                  --- @type number
+
+--- @alias LovrIUIShaderName "color" | "font" | "image" | "msdf"
+
+--- @class LovrIUIGraphics: IUIGraphicsBackend
+--- @field pass Pass
+local graphics = {}
+
+--- @param shader LovrIUIShaderName
+local function setShader(shader)
+    local targetShader = nil --- @type Shader?
+    if shader == "color" then
+        if currentClip then
+            targetShader = colorClipShader
+        end
+    elseif shader == "font" then
+        if currentClip then
+            targetShader = fontClipShader
+        end
+    elseif shader == "image" then
+        if currentClip then
+            targetShader = imageClipShader
+        else
+            targetShader = imageUnclippedShader
+        end
+    elseif shader == "msdf" then
+        if currentClip then
+            targetShader = msdfImageClipShader
+        else
+            targetShader = msdfImageUnclippedShader
+        end
+    end
+
+    local targetSampler = linearImageSampler
+
+    if currentImageFilter == "nearest" then
+        targetSampler = nearestImageSampler
+    end
+
+    if targetShader ~= currentShader then
+        graphics.pass:setShader(targetShader --[[@as any]])
+        currentShader = targetShader
+
+        if shader == "image" then
+            graphics.pass:send("useAAUV", currentImageFilter == "smooth")
+            graphics.pass:send("imageSampler", targetSampler)
+            isFilterDirty = false
+        elseif shader == "msdf" then
+            graphics.pass:send("msdfSampler", targetSampler)
+        end
+    end
+
+    if isFilterDirty then
+        if shader == "image" then
+            graphics.pass:send("useAAUV", currentImageFilter == "smooth")
+            graphics.pass:send("imageSampler", targetSampler)
+        elseif shader == "msdf" then
+            graphics.pass:send("msdfSampler", targetSampler)
+        end
+        isFilterDirty = false
+    end
+
+    if currentShader and currentClip and isClipDirty then
+        local windowCenter = currentWindow.center
+
+        isClipDirty = false
+
+        local left = currentClip[1]
+        local top = currentClip[2]
+        local right = left + currentClip[3]
+        local bottom = top + currentClip[4]
+
+        left = (left - (currentWindow.w / 2)) / currentWindow.ppm
+        top = -(top - (currentWindow.h / 2)) / currentWindow.ppm
+        right = (right - (currentWindow.w / 2)) / currentWindow.ppm
+        bottom = -(bottom - (currentWindow.h / 2)) / currentWindow.ppm
+
+        local q = currentWindow.rotation
+
+        local leftDir = vec3(1, 0, 0):rotate(q)
+        local topDir = vec3(0, -1, 0):rotate(q)
+        local rightDir = vec3(-1, 0, 0):rotate(q)
+        local bottomDir = vec3(0, 1, 0):rotate(q)
+
+        local topLeftVector = vec3(left, top, 0)
+        local bottomRightVector = vec3(right, bottom, 0)
+
+        topLeftVector = topLeftVector:rotate(q)
+        bottomRightVector = bottomRightVector:rotate(q)
+
+        topLeftVector = topLeftVector + windowCenter
+        bottomRightVector = bottomRightVector + windowCenter
+
+        graphics.pass:send("ClipPlanes", {
+            centers = {
+                topLeftVector,
+                topLeftVector,
+                bottomRightVector,
+                bottomRightVector,
+            },
+            directions = {
+                leftDir,
+                topDir,
+                rightDir,
+                bottomDir,
+            }
+        })
+    end
+end
+
+--- @param clip number[]?
+local function setClip(clip)
+    if clip ~= nil then
+        if currentClip == nil then
+            isClipDirty = true
+        else
+            for i = 1, #clip do
+                if clip[i] ~= currentClip[i] then
+                    isClipDirty = true
+                    break
+                end
+            end
+        end
+    end
+
+    currentClip = clip
+end
+
+--- @param filter IUIImageFilter
+local function setFilter(filter)
+    if filter ~= currentImageFilter then
+        currentImageFilter = filter
+        isFilterDirty = true
+    end
+end
+
+local function nineSliceMesh(nineSlice, x, y, w, h)
+    local image = nineSlice.image --- @type Texture
+
+    local iw, ih = image:getDimensions()
+
+    local l, t, r, b = nineSlice.l, nineSlice.t, nineSlice.r, nineSlice.b
+    local uvl, uvt, uvr, uvb = l / iw, t / ih, (iw - r) / iw, (ih - b) / ih
+    local wh = windowHeight
+
+    local mesh = lovr.graphics.newMesh(
+        {
+            { "VertexPosition", "vec2" },
+            { "VertexUV",       "vec2" },
+        },
+        {
+            { x,         wh - (y),         0,   0 },
+            { x + l,     wh - (y),         uvl, 0 },
+            { x + w - r, wh - (y),         uvr, 0 },
+            { x + w,     wh - (y),         1,   0 },
+
+            { x,         wh - (y + t),     0,   uvt },
+            { x + l,     wh - (y + t),     uvl, uvt },
+            { x + w - r, wh - (y + t),     uvr, uvt },
+            { x + w,     wh - (y + t),     1,   uvt },
+
+            { x,         wh - (y + h - b), 0,   uvb },
+            { x + l,     wh - (y + h - b), uvl, uvb },
+            { x + w - r, wh - (y + h - b), uvr, uvb },
+            { x + w,     wh - (y + h - b), 1,   uvb },
+
+            { x,         wh - (y + h),     0,   1 },
+            { x + l,     wh - (y + h),     uvl, 1 },
+            { x + w - r, wh - (y + h),     uvr, 1 },
+            { x + w,     wh - (y + h),     1,   1 },
+        }
+    )
+
+    mesh:setIndices({
+        1, 5, 2, 2, 5, 6,
+        2, 6, 3, 3, 6, 7,
+        3, 7, 4, 4, 7, 8,
+
+        5, 9, 6, 6, 9, 10,
+        6, 10, 7, 7, 10, 11,
+        7, 11, 8, 8, 11, 12,
+
+        9, 13, 10, 10, 13, 14,
+        10, 14, 11, 11, 14, 15,
+        11, 15, 12, 12, 15, 16,
+    })
+
+    return image, mesh
+end
+
+--- @param lib IUILib
+--- @param backend LovrIUIBackend
+function graphics.load(lib, backend)
+    iui = lib
+        
+    colorClipShader = lovr.graphics.newShader(
+        backend.resourcePath .. "shaders/ui-clip.glsl", "unlit"
+    )
+
+    fontClipShader = lovr.graphics.newShader(
+        backend.resourcePath .. "shaders/ui-clip.glsl", "font"
+    )
+
+    imageClipShader = lovr.graphics.newShader(
+        backend.resourcePath .. "shaders/ui-clip.glsl",
+        backend.resourcePath .. "shaders/ui-image.glsl"
+    )
+
+    imageUnclippedShader = lovr.graphics.newShader(
+        "unlit",
+        backend.resourcePath .. "shaders/ui-image.glsl"
+    )
+
+    msdfImageClipShader = lovr.graphics.newShader(
+        backend.resourcePath .. "shaders/ui-clip.glsl",
+        backend.resourcePath .. "shaders/ui-msdf.glsl"
+    )
+
+    msdfImageUnclippedShader = lovr.graphics.newShader(
+        "unlit",
+        backend.resourcePath .. "shaders/ui-msdf.glsl"
+    )
+
+    nearestImageSampler = lovr.graphics.newSampler {
+        wrap = { "clamp", "clamp", "clamp" },
+        filter = { "nearest", "nearest", "linear" },
+    }
+
+    linearImageSampler = lovr.graphics.newSampler {
+        wrap = { "clamp", "clamp", "clamp" },
+    }
+end
+
+--- @param window LovrIUIWorldWindow
+function graphics.setWindow(window)
+    currentWindow = window
+end
+
+function graphics.beginDraw(width, height)
+    windowWidth = width
+    windowHeight = height
+    currentImageFilter = "linear"
+    currentShader = nil
+    currentClip = nil
+    isFilterDirty = false
+    isClipDirty = false
+
+    local pass = graphics.pass
+
+    pass:setShader()
+    pass:setMaterial()
+
+    if iui.idiom == "desktop" then
+        pass:push()
+        pass:setDepthTest()
+
+        pass:setViewPose(1, mat4():identity(), false)
+        pass:setProjection(1, mat4():orthographic(
+            0, windowWidth, windowHeight, 0, -10, 10)
+        )
+    end
+end
+
+function graphics.endDraw()
+    if iui.idiom == "desktop" then
+        graphics.pass:pop()
+    end
+
+    graphics.pass:setShader()
+end
+
+function graphics.newFont(size, hinting, dpiscale)
+    local baseFontSize = 32
+    local font = lovr.graphics.newFont(baseFontSize)
+    font:setPixelDensity(baseFontSize / size)
+    return font
+end
+
+--- @param image Texture
+function graphics.getImageDimensions(image)
+    return image:getDimensions()
+end
+
+function graphics.clip(x, y, w, h)
+    if iui.idiom == "desktop" then
+        if x then
+            local wx, wy, ww, wh = 0, 0, windowWidth, windowHeight
+            local wmx, wmy = wx + ww, wy + wh
+            local mx, my = x + w, y + h
+
+            local dminX, dminY = math.max(x, wx), math.max(y, wy)
+            local dmaxX, dmaxY = math.min(mx, wmx), math.min(my, wmy)
+            local dx, dy, dw, dh = dminX, dminY, dmaxX - dminX, dmaxY - dminY
+
+            if dx < 0 or dy < 0 or dw < 0 or dh < 0 then
+                graphics.pass:setScissor(0, 0, 0, 0)
+            else
+                local dpi = lovr.system.getWindowDensity()
+                graphics.pass:setScissor(dx * dpi, dy * dpi, dw * dpi, dh * dpi)
+            end
+        else
+            graphics.pass:setScissor()
+        end
+    else
+        if x then
+            setClip({ x, y, w, h })
+        else
+            setClip(nil)
+        end
+    end
+end
+
+function graphics.setColor(r, g, b, a)
+    graphics.pass:setColor(r, g, b, a)
+end
+
+function graphics.rectangle(x, y, w, h, rx, ry)
+    setShader("color")
+    if (rx or 0) == 0 and (ry or 0) == 0 then
+        graphics.pass:setBlendMode()
+    end
+    graphics.pass:roundrect(x + w * 0.5, windowHeight - (y + h * 0.5), 0, w, h, 0, 0, 0, 0, 0, rx)
+    graphics.pass:setBlendMode("alpha", "alphamultiply")
+end
+
+function graphics.circle(x, y, r)
+    setShader("color")
+    graphics.pass:circle(x, windowHeight - y, 0, r)
+end
+
+function graphics.setFont(f)
+    graphics.pass:setFont(f)
+end
+
+function graphics.print(s, x, y)
+    setShader("font")
+    graphics.pass:text(s, x, windowHeight - y, 0, 1, 0, 0, 1, 0, 0, "left", "top")
+end
+
+--- @param image Texture
+function graphics.image(image, filter, x, y, w, h)
+    setFilter(filter)
+    setShader("image")
+    graphics.pass:setMaterial(image)
+    graphics.pass:plane(x + w * 0.5, windowHeight - (y + h * 0.5), 0, w, h)
+    graphics.pass:setMaterial()
+end
+
+function graphics.nineSlice(nineSlice, filter, x, y, w, h)
+    local image, mesh = nineSliceMesh(nineSlice, x, y, w, h)
+
+    setFilter(filter)
+    setShader("image")
+
+    graphics.pass:setMaterial(image)
+
+    graphics.pass:draw(mesh)
+    graphics.pass:setMaterial()
+end
+
+function graphics.msdfImage(image, x, y, w, h)
+    setFilter("linear")
+    setShader("msdf")
+    graphics.pass:setMaterial(image)
+    graphics.pass:plane(x + w * 0.5, windowHeight - (y + h * 0.5), 0, w, h)
+    graphics.pass:setMaterial()
+end
+
+function graphics.msdfNineSlice(nineSlice, x, y, w, h)
+    local image, mesh = nineSliceMesh(nineSlice, x, y, w, h)
+
+    setFilter("linear")
+    setShader("msdf")
+    graphics.pass:setMaterial(image)
+
+    graphics.pass:draw(mesh)
+    graphics.pass:setMaterial()
+end
+
+return graphics

src/lovr/lib/lovr-iui/init.lua

@@ -0,0 +1,144 @@
+local iui --- @type IUILib
+
+local currentPath = (...):gsub('%.init$', '') .. "."
+local resourcePath = currentPath:gsub("%.", "/")
+
+--- @type LovrIUISystem
+local system = require(currentPath .. "system")
+
+--- @type LovrIUIGraphics
+local graphics = require(currentPath .. "graphics")
+
+--- @type LovrIUIWorldWindow
+local worldWindow = require(currentPath .. "world-window")
+
+--- @type LovrIUIVRInput
+local input = require(currentPath .. "vr-input")
+
+local currentWorldWindow                  --- @type LovrIUIWorldWindow
+local desktopIdiomFullscreenWindowManager --- @type IUIWindowManager
+local desktopIdiomMouseRootContext        --- @type IUIMouseRootContext
+
+--- @class LovrIUIBackend: IUIBackend
+--- @field mouse any
+local backend = {
+    graphics = graphics,
+    system = system,
+    resourcePath = resourcePath,
+    worldWindow = worldWindow,
+    input = input,
+}
+
+function backend.config(config)
+    if not config.idiom then
+        if lovr.headset then
+            config.idiom = "vr"
+        else
+            config.idiom = "desktop"
+        end
+    end
+
+    if not config.detail then
+        if config.idiom == "vr" then
+            config.detail = "high"
+        else
+            if lovr.system.getWindowDensity() > 1 then
+                config.detail = "high"
+            else
+                config.detail = "low"
+            end
+        end
+    end
+end
+
+function backend.load(lib)
+    iui = lib
+
+    system.load(lib, backend)
+    graphics.load(lib, backend)
+    input.load(lib, backend)
+    worldWindow.load(lib, backend)
+
+    if iui.idiom == "desktop" then
+        desktopIdiomMouseRootContext = iui.input.mouse.newRootContext()
+        iui.input.mouse.setRootContext(desktopIdiomMouseRootContext)
+    end
+end
+
+--- @param dt number
+function backend.beginFrame(dt)
+    if iui.idiom == "vr" then
+        input.beginFrame(dt)
+    end
+end
+
+function backend.endFrame()
+    if iui.idiom == "vr" then
+        input.endFrame()
+    end
+end
+
+--- @param newWorldWindow LovrIUIWorldWindow
+function backend.setCurrentWorldWindow(newWorldWindow)
+    currentWorldWindow = newWorldWindow
+end
+
+function backend.getFullscreenWindowManager()
+    if iui.idiom == "desktop" then
+        if desktopIdiomFullscreenWindowManager == nil then
+            desktopIdiomFullscreenWindowManager = iui.newWindowManager()
+        end
+
+        return desktopIdiomFullscreenWindowManager
+    elseif iui.idiom == "vr" then
+        return currentWorldWindow:getFullscreenWindowManager()
+    end
+end
+
+--- @param x number
+--- @param y number
+--- @param dx number
+--- @param dy number
+function backend.mousemoved(x, y, dx, dy)
+    iui.input.mouse("move", 0, x, y, dx, dy)
+end
+
+--- @param x number
+--- @param y number
+--- @param button number
+function backend.mousepressed(x, y, button)
+    iui.input.mouse("down", button, x, y, 0, 0)
+end
+
+--- @param x number
+--- @param y number
+--- @param button number
+function backend.mousereleased(x, y, button)
+    iui.input.mouse("up", button, x, y, 0, 0)
+end
+
+--- @param x number
+--- @param y number
+function backend.wheelmoved(x, y)
+    iui.input.mouse("scroll", 0, 0, 0, x, y)
+end
+
+--- @param key KeyCode
+--- @param scancode number
+--- @param isRepeat boolean
+function backend.keypressed(key, scancode, isRepeat)
+    iui.input.keyboard("down", key, isRepeat)
+end
+
+--- @param key KeyCode
+--- @param scancode number
+function backend.keyreleased(key, scancode)
+    iui.input.keyboard("up", key, false)
+end
+
+--- @param text string
+function backend.textinput(text)
+    iui.input.text(text)
+end
+
+return backend

src/lovr/lib/lovr-iui/shaders/ui-clip.glsl

@@ -0,0 +1,13 @@
+uniform ClipPlanes {
+    vec3 centers[4];
+    vec3 directions[4];
+};
+
+vec4 lovrmain() {
+    ClipDistance[0] = dot(PositionWorld - centers[0], directions[0]);
+    ClipDistance[1] = dot(PositionWorld - centers[1], directions[1]);
+    ClipDistance[2] = dot(PositionWorld - centers[2], directions[2]);
+    ClipDistance[3] = dot(PositionWorld - centers[3], directions[3]);
+
+    return DefaultPosition;
+}

src/lovr/lib/lovr-iui/shaders/ui-image.glsl

@@ -0,0 +1,29 @@
+uniform bool useAAUV;
+uniform sampler imageSampler;
+
+vec2 getAAUV(texture2D tex, vec2 uv) {
+    vec2 texSize = textureSize(tex, 0);
+    vec2 pixelSpaceTexCoord = uv * texSize;
+    vec2 centerCoord = floor(pixelSpaceTexCoord - 0.5f) + 0.5f;
+    vec2 halfFWidth = fwidth(pixelSpaceTexCoord) * 0.5f;
+    vec2 offset = smoothstep(
+        0.5f - halfFWidth,
+        0.5f + halfFWidth,
+        pixelSpaceTexCoord - centerCoord
+    );
+    vec2 aauv = (centerCoord + offset) / texSize;
+
+    return aauv;
+}
+
+vec4 lovrmain() {
+    vec2 filteredUV;
+
+    if (useAAUV) {
+        filteredUV = getAAUV(ColorTexture, UV);
+    } else {
+        filteredUV = UV;
+    }
+
+    return Color * texture(sampler2D(ColorTexture, imageSampler), filteredUV);
+}

src/lovr/lib/lovr-iui/shaders/ui-msdf.glsl

@@ -0,0 +1,25 @@
+uniform sampler msdfSampler;
+
+vec2 squared(vec2 v) {
+    return v * v;
+}
+
+float screenPxRange() {
+    vec2 unitRange = vec2(2) / textureSize(ColorTexture, 0);
+    vec2 screenTexSize = inversesqrt(squared(dFdx(UV)) + squared(dFdy(UV)));
+    
+    return max(0.5 * dot(unitRange, screenTexSize), 1.0);
+}
+
+float median(float a, float b, float c) {
+    return max(min(a, b), min(max(a, b), c));
+}
+
+vec4 lovrmain() {
+    vec3 msd = texture(sampler2D(ColorTexture, msdfSampler), UV).rgb;
+    float sd = median(msd.r, msd.g, msd.b);
+    float screenPxDistance = screenPxRange() * (sd - 0.5);
+    float opacity = clamp(screenPxDistance + 0.5, 0.0, 1.0);
+
+    return vec4(Color.rgb, Color.a * opacity);
+}

src/lovr/lib/lovr-iui/system.lua

@@ -0,0 +1,75 @@
+local iui --- @type IUILib
+
+local mouse
+
+--- @param filename string
+--- @return Texture
+local function loadLinearTexture(filename)
+    return lovr.graphics.newTexture(iui.resourcePath .. filename, {
+        linear = true, mipmaps = false
+    })
+end
+
+--- @class LovrIUISystem: IUISystemBackend
+--- @field defaultCursor Texture
+--- @field currentCursor Texture?
+--- @field inactiveCursor Texture
+local system = {}
+
+--- @param lib IUILib
+--- @param backend LovrIUIBackend
+function system.load(lib, backend)
+    iui = lib
+
+    system.defaultCursor = loadLinearTexture("assets/cursor-default_sdf.png")
+    system.inactiveCursor = loadLinearTexture("assets/cursor-inactive_sdf.png")
+    system.currentCursor = system.defaultCursor
+
+    if iui.idiom == "desktop" then
+        mouse = backend.mouse
+
+        if not mouse then
+            error("Backend requires `mouse` library in desktop mode")
+        end
+    end
+end
+
+function system.getOS()
+    return lovr.system.getOS()
+end
+
+function system.getTimestamp()
+    return lovr.timer.getTime()
+end
+
+function system.getSystemCursor(name)
+    if iui.idiom == "desktop" then
+        return mouse.getSystemCursor(name)
+    end
+
+    name = "assets/cursor-" .. name .. "_sdf.png"
+
+    return loadLinearTexture(name)
+end
+
+function system.setCursor(cursor)
+    if iui.idiom == "desktop" then
+        mouse.setCursor(cursor)
+    end
+
+    system.currentCursor = (cursor --[[@as any]]) or system.defaultCursor
+end
+
+function system.getMSDFImage(name)
+    return loadLinearTexture(name)
+end
+
+function system.getDPI()
+    return lovr.system.getWindowDensity()
+end
+
+function system.quit()
+    lovr.event.quit()
+end
+
+return system

src/lovr/lib/lovr-iui/vr-input.lua

@@ -0,0 +1,309 @@
+local iui          --- @type IUILib
+local system       --- @type LovrIUISystem
+
+local cursorShader --- @type Shader
+
+local cursorSampler = lovr.graphics.newSampler {
+    wrap = { "clamp", "clamp", "clamp" }
+}
+
+--- @class (exact) TrackedIntersection
+--- @field worldPos Vec3
+--- @field uiPos Vec2
+--- @field dist number
+--- @field fuzzyInside number
+--- @field window LovrIUIWorldWindow
+
+--- @class (exact) InputWindowSession
+--- @field activeHand? Device
+--- @field hadHover boolean
+--- @field hadActive boolean
+
+--- @type Device[]
+local devices = {}
+
+--- @type table<Device, TrackedIntersection[]>
+local intersections = {}
+
+--- @type table<LovrIUIWorldWindow, InputWindowSession>
+local windowSessions = {}
+
+--- @type table<LovrIUIWorldWindow, InputWindowSession>
+local newWindowSessions = {}
+
+--- @type table<Device, LovrIUIWorldWindow>
+local hoveredWindows = {}
+
+--- @param rayPos Vec3
+--- @param rayDir Vec3
+--- @param planePos Vec3
+--- @param planeDir Vec3
+--- @return Vec3? intersection, number distance
+local function raycast(rayPos, rayDir, planePos, planeDir)
+    local dot = rayDir:dot(planeDir)
+    -- Reject glancing rays, and rays coming from behind the plane.
+    if dot >= -0.001 then
+        return nil, 0
+    else
+        --- @type number
+        local distance = (planePos - rayPos):dot(planeDir) / dot
+        if distance > 0 then
+            return rayPos + rayDir * distance, distance
+        else
+            return nil, 0
+        end
+    end
+end
+
+--- @class LovrIUIVRInput
+local input = {}
+
+--- @param lib IUILib
+--- @param backend LovrIUIBackend
+function input.load(lib, backend)
+    iui = lib
+
+    system = backend.system
+
+    if iui.idiom == "vr" then
+        cursorShader = lovr.graphics.newShader(
+            "font", backend.resourcePath .. "shaders/ui-msdf.glsl"
+        )
+
+        devices = {
+            "hand/right",
+            "hand/left",
+        }
+    end
+end
+
+--- @param dt number
+function input.beginFrame(dt)
+    intersections = {}
+    newWindowSessions = {}
+end
+
+function input.endFrame()
+    -- The window sessions table consists of only the windows we encountered
+    -- this frame.
+    windowSessions = newWindowSessions
+
+    -- Buzz controllers on hover.
+    for window, session in pairs(windowSessions) do
+        iui.input.mouse.setRootContext(window.mouse)
+        iui.input.mouse.endFrame()
+
+        local hasHover, hasActive = window:getHasHover(), window:getHasActive()
+        hasHover = hasHover or hasActive
+
+        if session.activeHand then
+            if hasHover and hasHover ~= session.hadHover then
+                lovr.headset.vibrate(session.activeHand, 0.2, 0.025)
+            end
+
+            if hasActive ~= session.hadActive then
+                lovr.headset.vibrate(session.activeHand, 0.4, 0.03)
+            end
+        end
+
+        session.hadHover, session.hadActive = hasHover, hasActive
+    end
+
+    -- Empty the `hoveredWindows` table, but only for hands that aren't the
+    -- `activeHand` of a window that has an `activeID`.
+    for device, window in pairs(hoveredWindows) do
+        local hasActive = window:getHasActive()
+        local isActiveHand = false
+
+        if hasActive then
+            for _, session in pairs(windowSessions) do
+                if session.activeHand == device then
+                    isActiveHand = true
+                    break
+                end
+            end
+        end
+
+        if not isActiveHand then
+            hoveredWindows[device] = nil
+        end
+    end
+
+    -- Update the window associated with each hand.
+    for device, ints in pairs(intersections) do
+        -- If this device is in `hoveredWindows`, then it's the `activeHand` of
+        -- a window, so we don't change its assignment.
+        if hoveredWindows[device] then
+            goto continue
+        end
+
+        -- Find the closest intersection.
+        local closest = ints[1]
+        for _, int in ipairs(ints) do
+            if int.fuzzyInside == closest.fuzzyInside then
+                if int.dist < closest.dist then
+                    closest = int
+                end
+            elseif int.fuzzyInside > closest.fuzzyInside then
+                closest = int
+            end
+        end
+
+        -- Assign the hand to the window
+        hoveredWindows[device] = closest.window
+
+        ::continue::
+    end
+end
+
+--- @param window LovrIUIWorldWindow
+function input.beginWorldWindow(window)
+    --- @type InputWindowSession
+    local session = windowSessions[window] or {
+        hadHover = false,
+        hadActive = false,
+    }
+
+    newWindowSessions[window] = session
+
+    local center = window.center
+    local rotation = window.rotation
+
+    for _, device in ipairs(devices) do
+        if lovr.headset.isTracked(device) then
+            local rayPos = vec3(lovr.headset.getPosition(device .. '/point'))
+            local rayDir = vec3(lovr.headset.getDirection(device .. '/point'))
+
+            local hit, dist = raycast(rayPos, rayDir, center, rotation:direction() * -1)
+
+            local mx, my = -1, -1
+            if hit then
+                -- hit is in worldspace, convert to ui space
+                hit = (hit - center):rotate(quat(rotation):conjugate()) * window.ppm
+                mx, my = hit.x + window.w / 2, window.h * 0.5 - hit.y
+                local fuzzyInside = window:fuzzyInside(mx, my)
+
+                if fuzzyInside > 0 then
+                    if hoveredWindows[device] == window then
+                        local canGrabActive = not window:getHasActive()
+                        canGrabActive = canGrabActive and (lovr.headset.wasPressed(device, "trigger"))
+
+                        if session.activeHand and session.activeHand ~= device then
+                            if lovr.headset.isDown(session.activeHand, "grip") then
+                                canGrabActive = false
+                            end
+                        end
+
+                        if session.activeHand == nil or canGrabActive then
+                            session.activeHand = device
+                            iui.input.mouse.resetVelocity()
+                        end
+                    end
+
+                    intersections[device] = intersections[device] or {}
+                    table.insert(intersections[device], {
+                        worldPos = hit,
+                        uiPos = Vec2(mx, my),
+                        dist = dist,
+                        fuzzyInside = fuzzyInside,
+                        window = window,
+                    })
+
+                    mx, my = math.floor(mx), math.floor(my)
+                end
+
+                if hoveredWindows[device] ~= window and session.activeHand == device then
+                    session.activeHand = nil
+
+                    iui.input.mouse("move", 0, -100, -100, 0, 0)
+                end
+
+                if session.activeHand == device then
+                    local dx = mx - iui.input.mouse.x
+                    local dy = my - iui.input.mouse.y
+                    iui.input.mouse("move", 0, mx, my, dx, dy)
+
+                    if lovr.headset.isDown(device, "grip") then
+                        if not iui.input.keyboard.down:has("lctrl") then
+                            iui.input.keyboard("down", "lctrl", false)
+                        end
+                    else
+                        if iui.input.keyboard.down:has("lctrl") then
+                            iui.input.keyboard("up", "lctrl", false)
+                        end
+                    end
+
+                    if lovr.headset.wasPressed(device, "trigger") then
+                        iui.input.mouse("down", 1, mx, my, 0, 0)
+                    end
+
+                    if lovr.headset.wasReleased(device, "trigger") then
+                        iui.input.mouse("up", 1, mx, my, 0, 0)
+                    end
+
+                    local sx, sy = lovr.headset.getAxis(device, "thumbstick")
+                    iui.input.mouse.scrollX = sx
+                    iui.input.mouse.scrollY = sy
+
+                    if window:fuzzyInside(mx, my) <= 0 then
+                        if not window:getHasActive() then
+                            session.activeHand = nil
+                        end
+                    end
+                end
+            end
+        end
+    end
+end
+
+--- @param window LovrIUIWorldWindow
+function input.endWorldWindow(window)
+end
+
+--- @param pass Pass
+--- @param window LovrIUIWorldWindow
+function input.draw(pass, window)
+    for device, testWindow in pairs(hoveredWindows) do
+        if window ~= testWindow or intersections[device] == nil then
+            goto outerContinue
+        end
+
+        for _, intersection in ipairs(intersections[device]) do
+            if intersection.window ~= window then
+                goto innerContinue
+            end
+
+            local opacity = intersection.fuzzyInside
+            if opacity > 0 then
+                pass:setColor(1, 1, 1, opacity * opacity)
+
+                local session = windowSessions[window]
+
+                local cursor = nil
+                local manager = window.fullscreenWindowManager
+                if manager then
+                    cursor = iui.getCursor(manager.cursor) or system.defaultCursor
+                end
+
+                if session.activeHand ~= device then
+                    cursor = system.inactiveCursor
+                end
+
+                if cursor then
+                    local mx, my = intersection.uiPos:unpack()
+
+                    pass:setShader(cursorShader)
+                    pass:send("msdfSampler", cursorSampler)
+                    pass:draw(cursor, mx, window.h - my, 0, 32)
+                    pass:setShader()
+                end
+            end
+
+            ::innerContinue::
+        end
+
+        ::outerContinue::
+    end
+end
+
+return input

src/lovr/lib/lovr-iui/world-window.lua

@@ -0,0 +1,180 @@
+local iui      --- @type IUILib
+local backend  --- @type LovrIUIBackend
+local graphics --- @type LovrIUIGraphics
+local input    --- @type LovrIUIVRInput
+
+--- @class (exact) IUIWorldWindowProps
+--- @field center? Vec3 Defaults to { x = 0, y = 1.5, z = -1 }
+--- @field rotation? Quat Defaults to { 0, 0, 0, 1 }
+--- @field ppm? number Defaults to 1000
+--- @field w? number Defaults to 1280
+--- @field h? number Defaults to 720
+
+--- @class LovrIUIWorldWindow
+--- @field fullscreenWindowManager? IUIWindowManager The window manager that fills the world window
+--- @field mouse IUIMouseRootContext Mouse input data for the window
+--- @field center Vec3 The center of the window, in worldspace
+--- @field rotation Quat The direction the window is facing
+--- @field ppm number The scale of the window, in points per meter
+--- @field w number The width of the window, in points
+--- @field h number The height of the window, in points
+local WorldWindow = {}
+WorldWindow.__index = WorldWindow
+
+--- @param lib IUILib
+--- @param theBackend LovrIUIBackend
+function WorldWindow.load(lib, theBackend)
+    iui = lib
+    backend = theBackend
+    graphics = backend.graphics
+    input = backend.input
+end
+
+--- @param props? IUIWorldWindowProps
+--- @return LovrIUIWorldWindow
+function WorldWindow.new(props)
+    props = props or {}
+
+    --- @type LovrIUIWorldWindow
+    local output = {
+        mouse = iui.input.mouse.newRootContext(),
+        center = props.center or Vec3(0, 1.5, -1),
+        rotation = props.rotation or Quat(),
+        ppm = props.ppm or 1000,
+        w = props.w or 1280,
+        h = props.h or 720,
+    }
+    setmetatable(output, WorldWindow)
+
+    return output
+end
+
+--- @param x number
+--- @param y number
+--- @return number insideAmount
+function WorldWindow:fuzzyInside(x, y)
+    local overflow = 60
+    local inside = 1
+
+    local closestX = iui.utils.clamp(x, 0, self.w)
+    local closestY = iui.utils.clamp(y, 0, self.h)
+    local dx, dy = closestX - x, closestY - y
+    local d = math.sqrt(dx * dx + dy * dy)
+
+    inside = iui.utils.clamp(1 - d / overflow, 0, 1)
+
+    return inside
+end
+
+function WorldWindow:recenter()
+    local headPos = vec3(lovr.headset.getPosition("head"))
+    local headDir = vec3(lovr.headset.getDirection("head"))
+    local targetPos = headPos + (headDir * 1)
+
+    local yaw = math.atan2(-headDir[1], -headDir[3])
+    local pitch = -math.asin(-headDir[2])
+
+    self.center = Vec3(targetPos)
+    self.rotation = Quat(quat():setEuler(pitch, yaw, 0))
+end
+
+--- @return boolean
+function WorldWindow:beginFrame()
+    backend.setCurrentWorldWindow(self)
+    iui.input.mouse.setRootContext(self.mouse)
+
+    input.beginWorldWindow(self)
+
+    return true
+end
+
+function WorldWindow:endFrame()
+    input.endWorldWindow(self)
+end
+
+--- @return IUIWindowManager
+function WorldWindow:getFullscreenWindowManager()
+    if self.fullscreenWindowManager == nil then
+        self.fullscreenWindowManager = iui.newWindowManager()
+    end
+
+    return self.fullscreenWindowManager
+end
+
+--- @return boolean
+function WorldWindow:getHasHover()
+    if self.fullscreenWindowManager then
+        return self.fullscreenWindowManager.hoverID ~= nil
+    end
+
+    return false
+end
+
+--- @return boolean
+function WorldWindow:getHasActive()
+    if self.fullscreenWindowManager then
+        return self.fullscreenWindowManager.activeID ~= nil
+    end
+
+    return false
+end
+
+--- @param pass Pass
+function WorldWindow:draw(pass)
+    graphics.setWindow(self)
+    graphics.pass = pass
+
+    pass:push()
+
+    -- pass:setDepthOffset(-100, 0)
+    -- pass:setDepthWrite(false)
+    -- pass:setDepthTest()
+    pass:setMaterial()
+    pass:translate(self.center)
+    pass:rotate(self.rotation)
+    pass:scale(1 / self.ppm)
+    pass:translate(-self.w / 2, -self.h / 2, 0)
+
+    -- Backface
+    pass:setDepthTest("gequal")
+    pass:setDepthWrite(true)
+    pass:setColor(1, 1, 1, 0.5)
+    pass:setFaceCull("front")
+    pass:roundrect(
+        self.w / 2, self.h / 2, 0,
+        self.w, self.h, 0,
+        0, 0, 0, 0,
+        iui.style["vrWindowCornerRadius"]
+    )
+    pass:setFaceCull()
+
+    -- Widgets do not write depth
+    pass:setDepthWrite(false)
+    pass:setFaceCull("back")
+
+    local manager = self.fullscreenWindowManager
+    if manager then
+        iui.draw.setWindowManager(manager)
+        iui.draw()
+    end
+
+    -- pass:setDepthOffset(0, 0)
+    input.draw(pass, self)
+
+    -- Front depth face
+    pass:setDepthWrite(true)
+    pass:setColorWrite(false)
+    pass:roundrect(
+        self.w / 2, self.h / 2, 0,
+        self.w, self.h, 0,
+        0, 0, 0, 0,
+        iui.style["vrWindowCornerRadius"]
+    )
+    pass:setColorWrite(true)
+
+    pass:setFaceCull()
+
+    pass:pop()
+end
+
+return WorldWindow

src/lovr/lib/lovr-mouse/LICENSE

@@ -0,0 +1,19 @@
+Copyright (c) 2018 Bjorn Swenson
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

src/lovr/lib/lovr-mouse/init.lua

@@ -0,0 +1,160 @@
+assert(type(jit) == 'table' and lovr.system.getOS() ~= 'Android', 'lovr-mouse cannot run on this platform')
+local ffi = require 'ffi'
+local C = ffi.os == 'Windows' and ffi.load('glfw3') or ffi.C
+
+ffi.cdef [[
+  enum {
+    GLFW_CURSOR = 0x00033001,
+    GLFW_CURSOR_NORMAL = 0x00034001,
+    GLFW_CURSOR_HIDDEN = 0x00034002,
+    GLFW_CURSOR_DISABLED = 0x00034003,
+    GLFW_ARROW_CURSOR = 0x00036001,
+    GLFW_IBEAM_CURSOR = 0x00036002,
+    GLFW_CROSSHAIR_CURSOR = 0x00036003,
+    GLFW_HAND_CURSOR = 0x00036004,
+    GLFW_HRESIZE_CURSOR = 0x00036005,
+    GLFW_VRESIZE_CURSOR = 0x00036006
+  };
+
+  typedef struct {
+    int width;
+    int height;
+    unsigned char* pixels;
+  } GLFWimage;
+
+  typedef struct GLFWcursor GLFWcursor;
+  typedef struct GLFWwindow GLFWwindow;
+  typedef void(*GLFWmousebuttonfun)(GLFWwindow*, int, int, int);
+  typedef void(*GLFWcursorposfun)(GLFWwindow*, double, double);
+  typedef void(*GLFWscrollfun)(GLFWwindow*, double, double);
+
+  GLFWwindow* os_get_glfw_window(void);
+  int glfwGetInputMode(GLFWwindow* window, int mode);
+  void glfwSetInputMode(GLFWwindow* window, int mode, int value);
+  void glfwGetCursorPos(GLFWwindow* window, double* x, double* y);
+  void glfwSetCursorPos(GLFWwindow* window, double x, double y);
+  GLFWcursor* glfwCreateCursor(const GLFWimage* image, int xhot, int yhot);
+  GLFWcursor* glfwCreateStandardCursor(int kind);
+  void glfwSetCursor(GLFWwindow* window, GLFWcursor* cursor);
+  int glfwGetMouseButton(GLFWwindow* window, int button);
+  void glfwGetWindowSize(GLFWwindow* window, int* width, int* height);
+  void glfwDestroyCursor(GLFWcursor* cursor);
+  GLFWmousebuttonfun glfwSetMouseButtonCallback(GLFWwindow* window, GLFWmousebuttonfun callback);
+  GLFWcursorposfun glfwSetCursorPosCallback(GLFWwindow* window, GLFWcursorposfun callback);
+  GLFWcursorposfun glfwSetScrollCallback(GLFWwindow* window, GLFWscrollfun callback);
+]]
+
+local window = ffi.C.os_get_glfw_window()
+
+local mouse = {}
+
+-- LÖVR uses framebuffer scale for everything, but glfw uses window scale for events.
+-- It is necessary to convert between the two at all boundaries.
+function mouse.getScale()
+  local x, _ = ffi.new('int[1]'), ffi.new('int[1]')
+  C.glfwGetWindowSize(window, x, _)
+  return lovr.system.getWindowWidth() / x[0]
+end
+
+function mouse.getX()
+  local x = ffi.new('double[1]')
+  C.glfwGetCursorPos(window, x, nil)
+  return x[0] * mouse.getScale()
+end
+
+function mouse.getY()
+  local y = ffi.new('double[1]')
+  C.glfwGetCursorPos(window, nil, y)
+  return y[0] * mouse.getScale()
+end
+
+function mouse.getPosition()
+  local x, y = ffi.new('double[1]'), ffi.new('double[1]')
+  local scale = mouse.getScale()
+  C.glfwGetCursorPos(window, x, y)
+  return x[0] * scale, y[0] * scale
+end
+
+function mouse.setX(x)
+  local y = mouse.getY()
+  local scale = mouse.getScale()
+  C.glfwSetCursorPos(window, x / scale, y / scale)
+end
+
+function mouse.setY(y)
+  local x = mouse.getX()
+  local scale = mouse.getScale()
+  C.glfwSetCursorPos(window, x / scale, y / scale)
+end
+
+function mouse.setPosition(x, y)
+  local scale = mouse.getScale()
+  C.glfwSetCursorPos(window, x / scale, y / scale)
+end
+
+function mouse.isDown(button, ...)
+  if not button then return false end
+  return C.glfwGetMouseButton(window, button - 1) > 0 or mouse.isDown(...)
+end
+
+function mouse.getRelativeMode()
+  return C.glfwGetInputMode(window, C.GLFW_CURSOR) == C.GLFW_CURSOR_DISABLED
+end
+
+function mouse.setRelativeMode(enable)
+  C.glfwSetInputMode(window, C.GLFW_CURSOR, enable and C.GLFW_CURSOR_DISABLED or C.GLFW_CURSOR_NORMAL)
+end
+
+function mouse.newCursor(source, hotx, hoty)
+  if type(source) == 'string' or tostring(source) == 'Blob' then
+    source = lovr.data.newImage(source)
+  else
+    assert(tostring(source) == 'Image', 'Bad argument #1 to newCursor (Image expected)')
+  end
+  local image = ffi.new('GLFWimage', source:getWidth(), source:getHeight(), source:getPointer())
+  return ffi.gc(C.glfwCreateCursor(image, hotx or 0, hoty or 0), C.glfwDestroyCursor)
+end
+
+function mouse.getSystemCursor(kind)
+  local kinds = {
+    arrow = C.GLFW_ARROW_CURSOR,
+    ibeam = C.GLFW_IBEAM_CURSOR,
+    crosshair = C.GLFW_CROSSHAIR_CURSOR,
+    hand = C.GLFW_HAND_CURSOR,
+    sizewe = C.GLFW_HRESIZE_CURSOR,
+    sizens = C.GLFW_VRESIZE_CURSOR
+  }
+  assert(kinds[kind], string.format('Unknown cursor %q', tostring(kind)))
+  return ffi.gc(C.glfwCreateStandardCursor(kinds[kind]), C.glfwDestroyCursor)
+end
+
+function mouse.setCursor(cursor)
+  C.glfwSetCursor(window, cursor)
+end
+
+C.glfwSetMouseButtonCallback(window, function(target, button, action, mods)
+  if target == window then
+    local x, y = mouse.getPosition()
+    lovr.event.push(action > 0 and 'mousepressed' or 'mousereleased', x, y, button + 1, false)
+  end
+end)
+
+local px, py = mouse.getPosition()
+C.glfwSetCursorPosCallback(window, function(target, x, y)
+  if target == window then
+    local scale = mouse.getScale()
+    x = x * scale
+    y = y * scale
+    lovr.event.push('mousemoved', x, y, x - px, y - py, false)
+    px, py = x, y
+  end
+end)
+
+C.glfwSetScrollCallback(window, function(target, x, y)
+  if target == window then
+    local scale = mouse.getScale()
+    lovr.event.push('wheelmoved', x * scale, y * scale)
+  end
+end)
+
+return mouse

src/lovr/main.lua

@@ -0,0 +1,162 @@
+if os.getenv("LOCAL_LUA_DEBUGGER_VSCODE") == "1" then
+    require "lldebugger".start()
+end
+
+local util   = require "util"
+local launch = require "launch"
+
+local iui = require "lib.iui"
+local backend = require "lib.lovr-iui"
+
+-- modify for nested lovr path for api
+iui.resourcePath = "lovr/" .. iui.resourcePath
+backend.resourcePath = "lovr/" .. backend.resourcePath
+api.iui = iui
+api.backend = backend
+local ecs = api.ecs
+
+--- @type Texture
+local envTex
+
+--- @type LovrIUIWorldWindow
+local mainWindow
+
+function lovr.load()
+    if launch.mode == "desktop" then
+        backend.mouse = require "lib.lovr-mouse"
+
+        lovr.system.setKeyRepeat(true)
+    end
+
+    iui.load(backend)
+
+    api.exec( api.ext, "load")
+
+    if iui.idiom == "vr" then
+        lovr.headset.setPassthrough("opaque")
+
+        mainWindow = backend.worldWindow.new()
+        api.mainWindow = mainWindow
+    end
+end
+
+function lovr.update(dt)
+    if lovr.system.isKeyDown("escape") then
+        lovr.event.quit()
+    end
+    
+    ecs.update( ecs.world, pass, ecs.filter('updatesystem') )
+
+    iui.beginFrame(dt)
+
+    if iui.idiom == "desktop" then
+        -- In desktop mode, we use IUI's standard window API to fill the screen.
+        iui.beginWindow(lovr.system.getWindowDimensions())
+
+        api.exec( api.ext, "update", dt)
+
+        iui.endWindow()
+
+    elseif iui.idiom == "vr" then
+        -- In VR mode, we have access to the backend's `LovrIUIWorldWindow`
+        -- class, which handles windowing in world-space.
+        if mainWindow:beginFrame() then
+            iui.beginWindow(mainWindow.w, mainWindow.h)
+
+            api.exec( api.ext, "update", dt)
+
+            iui.endWindow()
+
+            mainWindow:endFrame()
+        end
+    end
+
+    iui.endFrame()
+end
+
+function lovr.draw(pass)
+    if iui.idiom == "desktop" then
+        backend.graphics.pass = pass
+
+        iui.draw()
+    end
+    if api.iui.idiom == "vr" then
+      pass:setClear(0.5, 0.5, 0.5)
+    end
+    api.exec(api.ext, "draw",pass)
+    ecs.update( ecs.world, pass, ecs.filter('drawsystem') )
+    if api.mainWindow then
+      api.mainWindow:draw(pass)
+    end
+    return false
+end
+
+function lovr.recenter()
+    if iui.idiom == "vr" then
+        mainWindow:recenter()
+    end
+end
+
+if launch.mode == "desktop" then
+    function lovr.mousemoved(x, y, dx, dy)
+        backend.mousemoved(x, y, dx, dy)
+    end
+
+    function lovr.mousepressed(x, y, button)
+        backend.mousepressed(x, y, button)
+    end
+
+    function lovr.mousereleased(x, y, button)
+        backend.mousereleased(x, y, button)
+    end
+
+    function lovr.wheelmoved(x, y)
+        backend.wheelmoved(x, y)
+    end
+
+    function lovr.keypressed(key, scancode, isRepeat)
+        backend.keypressed(key, scancode, isRepeat)
+    end
+
+    function lovr.keyreleased(key, scancode)
+        backend.keyreleased(key, scancode)
+    end
+
+    function lovr.textinput(text)
+        backend.textinput(text)
+    end
+end
+
+local initECS = function(ecs)
+  ecs.world   = ecs.world()
+
+  -- lovr.draw => ecs.drawsystem (render-logic thread)
+  local renderer = ecs.processingSystem()
+  renderer.filter     = ecs.requireAny('model')  -- add more types when needed
+  renderer.drawsystem = true
+  function renderer:process(obj, pass)
+    if obj['model'] ~= nil then 
+      pass:setMaterial()
+      pass:setCullMode('none')
+      pass:draw(
+        obj['model'], 
+        obj['x'] or 0, 
+        obj['y'] or 0,
+        obj['z'] or 0, 
+        1, 0, 1, 0, 0, 1)
+    end
+  end
+  ecs.addSystem( ecs.world, renderer )
+
+  -- lovr.update => ecs updatesystem (game-logic thread)
+  local update = ecs.processingSystem()
+  update.updatesystem = true 
+  update.filter = ecs.requireAll('update') -- *TODO* might need filter later
+  function update:process(obj, dt)
+    print_r(obj['data'])
+  end
+  ecs.addSystem( ecs.world, update )
+
+end
+
+initECS(api.ecs)

src/lovr/sample/.gitignore

@@ -0,0 +1,2 @@
+.DS_Store
+.vscode

src/lovr/sample/LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2026 Donald Hays
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

src/lovr/sample/README.md

@@ -0,0 +1,13 @@
+# IUI-SAMPLE
+
+A sample project for the [IUI](https://github.com/DonaldHays/iui) immediate mode
+GUI library.
+
+This sample shows many APIs and patterns for IUI, but is not a standalone
+project on its own. It can be used as a basis for sample projects that are tied
+to specific engines.
+
+# Projects That Use This Sample
+
+- [iui-sample-love](https://github.com/DonaldHays/iui-sample-love): LÖVE
+- [iui-sample-lovr](https://github.com/DonaldHays/iui-sample-lovr): LÖVR