WIP: tabs, docking, dragdrop, settings, logging, harness

tools/bundle.py

@@ -13,7 +13,7 @@ for dp, _, fn in os.walk(SRC):
         if f.endswith(".lua"):
             FILES[f] = open(os.path.join(dp, f)).read()
 
-ENTRY = ["imgui.lua", "imgui_impl_roblox.lua", "imgui_demo.lua"]  # run order
+ENTRY = ["imgui.lua", "imgui_impl_roblox.lua"] + sorted(f for f in FILES if f.startswith("imgui_demo"))  # run order
 
 names = set()
 for src in FILES.values():
@@ -27,8 +27,10 @@ out = ["--!native", "--!optimize 2", "-- GENERATED by tools/bundle.py from imgui
        "    if r == nil then r = __FILES[name](); if r == nil then r = true end; __LOADED[name] = r end",
        "    return r",
        "end", ""]
+linemap = []  # (first bundle line, file) for error -> source mapping (tools/test/run.py)
 for name, src in sorted(FILES.items()):
     out.append("__FILES[%r] = function()" % name)
+    linemap.append((sum(x.count("\n") + 1 for x in out) + 1, name))
     out.append(src.rstrip("\n"))
     out.append("end")
     out.append("")
@@ -40,6 +42,10 @@ for n in sorted(names):
     out.append("    %s = %s," % (n, n))
 out.append("}")
 
-os.makedirs(os.path.join(ROOT, "build"), exist_ok=True)
-open(os.path.join(ROOT, "build", "ImGui.luau"), "w").write("\n".join(out) + "\n")
+import sys
+OUT = sys.argv[1] if len(sys.argv) > 1 else os.path.join(ROOT, "build")
+os.makedirs(OUT, exist_ok=True)
+open(os.path.join(OUT, "ImGui.luau"), "w").write("\n".join(out) + "\n")
+import json
+json.dump(linemap, open(os.path.join(OUT, "ImGui.linemap.json"), "w"))
 print("wrote build/ImGui.luau (%d files, %d exports)" % (len(FILES), len(names)))

tools/test/PORTING.md

@@ -0,0 +1,54 @@
+# Porting rules (Dear ImGui docking branch -> this Lua/Luau port)
+
+Upstream reference: `tools/test/upstream/*.cpp|h` (ocornut/imgui `docking` branch, 1.93 WIP). Port semantics 1:1 from
+there, but keep this port's existing data structures and conventions. Read the surrounding existing Lua code first.
+
+## Runtime
+- Target is **Luau (Roblox)** only. All files are concatenated into one ModuleScript by `tools/bundle.py`; every
+  file shares one global namespace. Globals defined by one file are visible to the others at call time.
+- Each `imgui/*.lua` file is a function body in the bundle. New files must be loaded with `IM_INCLUDE"file.lua"`
+  from an existing file (files named `imgui_demo*.lua` are loaded automatically, after `imgui.lua`).
+- No `goto`, no `::labels::`, no `setfenv/getfenv`, no LuaJIT `bit`/`ffi`. Use `bit32`. For `continue` use
+  `repeat ... until true` with `break`, and an explicit flag when the loop itself must break out of the wrapper.
+- Luau has a limit of 200 locals per function and 255 upvalues; split huge functions (like demo sections) into
+  several local/global functions.
+
+## Conventions (follow what the port already does)
+- `ImVector`: 1-based `.Data`, `.Size`, methods `push_back/pop_back/resize/back/iter/erase/...` (imgui_h.lua).
+  Indices that C++ stores as 0-based *values* (e.g. column index, tab order) stay 0-based unless the surrounding
+  port code already shifted them; document `-- 0-based` / `-- 1-based` next to anything ambiguous.
+- `ImVec2(x, y)` stores `[1],[2]` with `.x/.y` aliases (metatable). Arithmetic operators exist. Prefer
+  `ImVec2_Copy(dst, src)` / `ImVec2_CopyV(dst, x, y)` when C++ assigns into an existing struct field.
+  `ImVec4`, `ImRect` (`.Min/.Max`) likewise.
+- Structs: constructor function `ImGuiFoo()` returning a table, methods on `MT.ImGuiFoo` with
+  `MT.ImGuiFoo.__index = MT.ImGuiFoo`. `local MT = ImGui.GetMetatables()`.
+- Flags/enums: tables like `ImGuiTableFlags.Resizable`; combine with `bit32.bor`, test with `bit32.band(...) ~= 0`.
+- Context: `local g = GImGui` (each file has its own local `GImGui` kept in sync; follow how the file you are in
+  does it). New fields on `ImGuiContext`/`ImGuiWindow`: add them to the constructor in imgui_internal.lua.
+- Strings: Lua strings + 1-based byte positions; `text_end` is exclusive. Editable text buffers are `char[]`
+  (byte tables), like `ImGui.InputText(label, buf, buf_size)`.
+- **Output parameters** (C++ `bool* p_open`, `float* v`, `int* current_item`...) become return values:
+  - bool-like widgets: `return pressed, new_v`  (Checkbox, RadioButton, Selectable, MenuItem, CheckboxFlags)
+  - scalar widgets: `return new_v, changed`  (Slider*/Drag*/Input* scalar, SliderAngle, Combo -> `new_idx, changed`)
+  - multi-component (`float v[3]`, ImVec4 colors, `char[]` buffers): table mutated in place, return `changed`
+  - `Begin(name, p_open)` style: `return open, visible` / follow existing `ImGui.Begin`.
+  When an existing similar function already exists, copy its convention exactly.
+- `static` locals in C++ become file-level upvalue tables / fields (demo uses a `static` table per section).
+- `IM_ASSERT(cond, msg)` exists. `IM_COL32(r,g,b,a)`, `ImMax/ImMin/ImClamp/ImLerp/ImFloor/ImTrunc` etc. exist.
+- Keep function names identical to upstream (`ImGui.TableNextRow`, `ImGui.TabBarLayout`, ...). Internal helpers
+  that are `static` in C++ become `local function` in the file.
+- Roblox can't do: OS clipboard (internal only), files/URLs (VFS `ImStd.ImFileLoadToMemory` only), multi-viewports,
+  gamepad. Port the code paths anyway where cheap; demo shows "(not supported on Roblox)" text instead of
+  widgets that cannot work.
+
+## Testing
+- `python3 tools/test/run.py` — runs main.client.luau 400 frames with scripted random input (mouse, clicks,
+  keys, typing). Errors print with `imgui/<file>.lua:<line>` mapped stack traces.
+- `--open` forces every CollapsingHeader/TreeNode open (exercises the whole demo). `--big` makes the demo
+  window 900x1000. `--png out.png` writes a screenshot (Read the PNG to look at it). `--check` asserts the
+  incremental renderer is pixel identical to a full redraw. `--main file.luau` runs your own test LocalScript
+  (copy main.client.luau as a template: `local G = require(ReplicatedStorage:WaitForChild("ImGui"))`, all
+  library globals are fields of `G`).
+- `python3 tools/test/missing.py [tables|widgets|imgui.cpp]` lists upstream functions not yet ported.
+- Several people edit the repo concurrently. Keep every file syntactically valid after each edit. If a run fails
+  because of an error in a file you don't own, wait a minute and retry instead of editing it.

tools/test/missing.py

@@ -0,0 +1,21 @@
+#!/usr/bin/env python3
+"""Lists upstream ImGui:: functions (tools/test/upstream/*.cpp, docking branch) that the Lua port doesn't define.
+  python3 tools/test/missing.py              # summary per upstream file
+  python3 tools/test/missing.py tables       # names missing from imgui_tables.cpp
+"""
+import os, re, sys
+HERE = os.path.dirname(os.path.abspath(__file__))
+ROOT = os.path.dirname(os.path.dirname(HERE))
+port = set()
+for f in os.listdir(os.path.join(ROOT, "imgui")):
+    if f.endswith(".lua"):
+        port.update(re.findall(r"function ImGui[.:](\w+)", open(os.path.join(ROOT, "imgui", f)).read()))
+filt = sys.argv[1] if len(sys.argv) > 1 else None
+for f in sorted(os.listdir(os.path.join(HERE, "upstream"))):
+    if not f.endswith(".cpp") or f == "imgui_demo.cpp": continue
+    if filt and filt not in f: continue
+    src = open(os.path.join(HERE, "upstream", f)).read()
+    names = sorted(set(re.findall(r"^[\w:<>*& ]+?\bImGui::(\w+)\(", src, re.M)))
+    miss = [n for n in names if n not in port]
+    print("%-20s %4d/%4d ported, missing %d" % (f, len(names) - len(miss), len(names), len(miss)))
+    if filt: print("  " + "\n  ".join(miss))

tools/test/roblox_mock.luau

@@ -0,0 +1,245 @@
+-- Minimal Roblox mock for running the imgui Roblox backend + the real CanvasDraw module in the Luau CLI.
+local realG = {} -- (no getfenv: it would mark the global env unsafe and deoptimize everything)
+FAKE_TIME = 0
+local SCREEN_W, SCREEN_H = 1920, 1080
+local NFRAMES = tonumber(ARG_FRAMES) or 400
+local FORCE = ARG_FORCE == true
+local DUMP_FRAMES = { [60] = true, [200] = true, [NFRAMES] = true }
+
+local function Signal()
+    local s = { conns = {} }
+    function s:Connect(fn)
+        local c = { fn = fn, Connected = true }
+        function c:Disconnect() c.Connected = false end
+        table.insert(s.conns, c)
+        return c
+    end
+    function s:Fire(...) for _, c in ipairs(s.conns) do if c.Connected then c.fn(...) end end end
+    return s
+end
+
+local V2 = {}
+V2.__index = V2
+local function v2(x, y) return setmetatable({ X = x or 0, Y = y or 0 }, V2) end
+V2.__add = function(a, b) return v2(a.X + b.X, a.Y + b.Y) end
+V2.__sub = function(a, b) return v2(a.X - b.X, a.Y - b.Y) end
+V2.__mul = function(a, b) if type(b) == "number" then return v2(a.X * b, a.Y * b) end return v2(a.X * b.X, a.Y * b.Y) end
+V2.__div = function(a, b) if type(b) == "number" then return v2(a.X / b, a.Y / b) end return v2(a.X / b.X, a.Y / b.Y) end
+V2.__eq = function(a, b) return a.X == b.X and a.Y == b.Y end
+local Vector2 = { new = v2, zero = v2(0, 0), one = v2(1, 1) }
+
+-- Enums: KeyCode values as in Roblox; unknown KeyCode names error (catches typos in the backend)
+local KEYCODES = {
+    Unknown = 0, Backspace = 8, Tab = 9, Return = 13, Escape = 27, Space = 32, Quote = 39, Comma = 44, Minus = 45, Period = 46, Slash = 47,
+    Semicolon = 59, Equals = 61, LeftBracket = 91, BackSlash = 92, RightBracket = 93, Backquote = 96, Delete = 127,
+    KeypadPeriod = 266, KeypadDivide = 267, KeypadMultiply = 268, KeypadMinus = 269, KeypadPlus = 270, KeypadEnter = 271, KeypadEquals = 272,
+    Up = 273, Down = 274, Right = 275, Left = 276, Insert = 277, Home = 278, End = 279, PageUp = 280, PageDown = 281,
+    CapsLock = 301, RightShift = 303, LeftShift = 304, RightControl = 305, LeftControl = 306, RightAlt = 307, LeftAlt = 308,
+    LeftSuper = 311, RightSuper = 312,
+}
+local digits = { "Zero", "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine" }
+for i = 0, 9 do KEYCODES[digits[i + 1]] = 48 + i; KEYCODES["Keypad" .. digits[i + 1]] = 256 + i end
+for i = 0, 25 do KEYCODES[string.char(65 + i)] = 97 + i end
+for i = 1, 15 do KEYCODES["F" .. i] = 281 + i end
+
+local Enum = setmetatable({}, { __index = function(t, enum_name)
+    local e = setmetatable({}, { __index = function(e, item)
+        local value = 0
+        if enum_name == "KeyCode" then value = KEYCODES[item]; assert(value, "invalid KeyCode " .. item) end
+        local it = { Name = item, Value = value, EnumType = enum_name }
+        rawset(e, item, it)
+        return it
+    end })
+    rawset(t, enum_name, e)
+    return e
+end })
+
+-- Instances
+local InstMethods = {}
+local InstMT = {}
+InstMT.__index = function(t, k)
+    if k == "Parent" then return rawget(t, "_parent") end
+    local m = InstMethods[k]; if m then return m end
+    for _, c in ipairs(rawget(t, "_children")) do if c.Name == k then return c end end
+    return nil
+end
+InstMT.__newindex = function(t, k, v)
+    if k == "Parent" then
+        local old = rawget(t, "_parent")
+        if old then local ch = rawget(old, "_children"); for i, c in ipairs(ch) do if c == t then table.remove(ch, i) break end end end
+        rawset(t, "_parent", v)
+        if v then table.insert(rawget(v, "_children"), t) end
+    else
+        rawset(t, k, v)
+    end
+end
+local function newInst(class, name, parent)
+    local o = setmetatable({ ClassName = class, Name = name or class, _children = {} }, InstMT)
+    if class == "ScreenGui" or class == "Frame" or class == "ImageLabel" then o.AbsoluteSize = v2(SCREEN_W, SCREEN_H) end
+    o.Visible = true
+    if class == "BindableEvent" then local sig = Signal(); rawset(o, "Event", sig); rawset(o, "Fire", function(_, ...) sig:Fire(...) end) end
+    if parent then o.Parent = parent end
+    return o
+end
+function InstMethods:FindFirstChild(name, recursive)
+    for _, c in ipairs(rawget(self, "_children")) do if c.Name == name then return c end end
+    if recursive then for _, c in ipairs(rawget(self, "_children")) do local r = c:FindFirstChild(name, true); if r then return r end end end
+    return nil
+end
+function InstMethods:WaitForChild(name) return assert(self:FindFirstChild(name), "WaitForChild would hang: " .. name) end
+function InstMethods:FindFirstChildOfClass(class) for _, c in ipairs(rawget(self, "_children")) do if c.ClassName == class then return c end end end
+function InstMethods:GetChildren() return table.clone(rawget(self, "_children")) end
+function InstMethods:IsA(class)
+    if class == "GuiObject" then return self.ClassName == "Frame" or self.ClassName == "ImageLabel" end
+    return self.ClassName == class
+end
+function InstMethods:Destroy() self.Parent = nil end
+
+-- Services
+local mouse = v2(0, 0)
+local keys_down = {}
+local UIS = {
+    InputBegan = Signal(), InputEnded = Signal(), InputChanged = Signal(), WindowFocused = Signal(), WindowFocusReleased = Signal(),
+}
+function UIS:GetMouseLocation() return mouse end
+function UIS:IsKeyDown(kc) return keys_down[kc] == true end
+
+local RunService = { Heartbeat = Signal(), Stepped = Signal(), PreAnimation = Signal(), RenderStepped = Signal() }
+local last_pixels -- last buffer written to an EditableImage
+local AssetService = {}
+function AssetService:CreateEditableImage(opts)
+    local img = { Size = opts.Size, Pixels = buffer.create(opts.Size.X * opts.Size.Y * 4) }
+    UPLOADS = 0
+    function img:WritePixelsBuffer(origin, size, buf) buffer.copy(img.Pixels, 0, buf); _G_UPLOADS = (_G_UPLOADS or 0) + 1 end
+    function img:Destroy() end
+    return img
+end
+local ReplicatedStorage = newInst("ReplicatedStorage")
+local PlayerGui = newInst("PlayerGui")
+local LocalPlayer = newInst("Player"); PlayerGui.Parent = LocalPlayer
+local services = {
+    UserInputService = UIS, RunService = RunService, AssetService = AssetService, ReplicatedStorage = ReplicatedStorage,
+    Players = { LocalPlayer = LocalPlayer }, HttpService = {}, GuiService = { GetGuiInset = function() return v2(0, 0), v2(0, 0) end },
+}
+local game = {}
+function game:GetService(name) services[name] = services[name] or {}; return services[name] end
+
+local fakeG = {} -- Roblox's shared _G
+local cache = {}
+local ROBLOX
+local function makeEnv(inst) return setmetatable({ script = inst }, { __index = ROBLOX }) end
+local GLOBAL_NAMES = { "game", "workspace", "Instance", "Enum", "Vector2", "Vector3", "UDim2", "Color3", "Content", "warn", "require", "script", "os" }
+-- Load like Roblox does but WITHOUT setfenv (which would disable Luau optimizations): Roblox globals become chunk locals.
+local function loadAsScript(src_name, inst)
+    local fn = SOURCE_FNS[src_name]
+    local vals = {}
+    for i, n in ipairs(GLOBAL_NAMES) do vals[i] = (n == "script") and inst or ROBLOX[n] end
+    return function() return fn(table.unpack(vals, 1, #GLOBAL_NAMES)) end
+end
+local function rbxrequire(inst)
+    assert(type(inst) == "table" and inst.ClassName == "ModuleScript", "require() expects a ModuleScript")
+    if cache[inst] then return cache[inst].v end
+    local r = table.pack(loadAsScript(rawget(inst, "_src"), inst)())
+    assert(r.n == 1, "Module code did not return exactly one value")
+    cache[inst] = { v = r[1] }
+    return r[1]
+end
+
+ROBLOX = setmetatable({
+    game = game, workspace = { CurrentCamera = { ViewportSize = v2(SCREEN_W, SCREEN_H) } }, require = rbxrequire, _G = fakeG,
+    Instance = { new = function(class) return newInst(class) end },
+    Enum = Enum, Vector2 = Vector2,
+    Vector3 = { new = function(x, y, z) return { X = x, Y = y, Z = z } end },
+    UDim2 = { new = function(...) return { ... } end, fromScale = function(...) return { ... } end, fromOffset = function(x, y) return { X = x, Y = y } end },
+    Color3 = { new = function(r, g, b) return { R = r or 0, G = g or 0, B = b or 0 } end },
+    Content = { fromObject = function(o) return { Object = o } end },
+    warn = function(...) print("WARN", ...) end,
+    os = { clock = function() return FAKE_TIME end, time = os.time },
+}, { __index = realG })
+
+local mod = newInst("ModuleScript", "ImGui", ReplicatedStorage); rawset(mod, "_src", "ImGui.luau")
+-- Run main.lua as a LocalScript
+local main = loadAsScript("main.client.luau", newInst("LocalScript", "main"))
+main()
+local G = cache[mod].v
+local render_time = 0
+local realDemo = G.ImGui.ShowDemoWindow
+local realCH = G.ImGui.CollapsingHeader
+G.ImGui.CollapsingHeader = function(...)
+    if ARG_OPEN then G.ImGui.SetNextItemOpen(true, G.ImGuiCond.Always) end
+    return realCH(...)
+end
+local realTN = G.ImGui.TreeNode
+G.ImGui.TreeNode = function(...)
+    if ARG_OPEN then G.ImGui.SetNextItemOpen(true, G.ImGuiCond.Always) end
+    return realTN(...)
+end
+G.ImGui.ShowDemoWindow = function(...)
+    if ARG_BIG then G.ImGui.SetNextWindowSize(G.ImVec2(900, 1000), G.ImGuiCond.Always) end
+    return realDemo(...)
+end
+local realRender = G.ImGui_ImplRoblox.RenderDrawData
+G.ImGui_ImplRoblox.RenderDrawData = function(dd)
+    if FORCE then G.ImGui.GetIO().BackendPlatformUserData.ForceRedraw = true end
+    local t0 = os.clock(); realRender(dd); render_time = render_time + os.clock() - t0
+end
+
+-- Drive frames with scripted (deterministic) input
+local seed = 12345
+local function rnd(n) seed = (seed * 1103515245 + 12345) % 2147483648; return seed % n end
+local function input(t, kc, pos) return { UserInputType = Enum.UserInputType[t], KeyCode = Enum.KeyCode[kc or "Unknown"], Position = pos or { X = 0, Y = 0, Z = 0 } } end
+local held = false
+local typing = { "H", "E", "L", "L", "O", "Space", "One", "Two", "Minus", "Backspace", "Left", "Return" }
+local hex = {}
+for i = 0, 255 do hex[i] = string.format("%02x", i) end
+
+local total = 0
+for frame = 1, NFRAMES do
+    local r = rnd(100)
+    if r < 40 then
+        mouse = v2(math.clamp(mouse.X + rnd(81) - 40, 0, SCREEN_W - 1), math.clamp(mouse.Y + rnd(81) - 40, 0, SCREEN_H - 1))
+    elseif r < 55 then
+        held = not held
+        if held then UIS.InputBegan:Fire(input("MouseButton1"), false) else UIS.InputEnded:Fire(input("MouseButton1"), false) end
+    elseif r < 60 then
+        UIS.InputChanged:Fire(input("MouseWheel", nil, { X = 0, Y = 0, Z = rnd(3) - 1 }), false)
+    elseif r < 75 then
+        local k = typing[rnd(#typing) + 1]
+        local shift = rnd(4) == 0
+        if shift then keys_down[Enum.KeyCode.LeftShift] = true; UIS.InputBegan:Fire(input("Keyboard", "LeftShift"), false) end
+        UIS.InputBegan:Fire(input("Keyboard", k), false)
+        UIS.InputEnded:Fire(input("Keyboard", k), false)
+        if shift then keys_down[Enum.KeyCode.LeftShift] = nil; UIS.InputEnded:Fire(input("Keyboard", "LeftShift"), false) end
+    elseif r < 90 then
+        mouse = v2(rnd(700), rnd(500))
+    end
+
+    FAKE_TIME = frame / 60
+    local t0 = os.clock()
+    RunService.Stepped:Fire(frame / 60, 1 / 60)
+    local dt = os.clock() - t0
+    if frame > 10 then total = total + dt end
+
+    if frame == 10 then render_time = 0; _G_UPLOADS = 0 end
+    if DUMP_FRAMES[frame] and ARG_DUMP then
+        local W, H = SCREEN_W, SCREEN_H
+        local screen = buffer.create(W * H * 4)
+        local gui = PlayerGui:FindFirstChild("ImGui")
+        for _, label in ipairs(gui:GetChildren()) do
+            if label.Visible then
+                local img, px, py = label.ImageContent.Object, label.Position.X, label.Position.Y
+                local tw, th = img.Size.X, img.Size.Y
+                for y = 0, th - 1 do
+                    if py + y < H then
+                        local n = math.min(tw, W - px)
+                        buffer.copy(screen, ((py + y) * W + px) * 4, img.Pixels, y * tw * 4, n * 4)
+                    end
+                end
+            end
+        end
+        local parts = {}
+        for i = 0, W * H * 4 - 1 do parts[#parts + 1] = hex[buffer.readu8(screen, i)] end
+        print(string.format("IMG %d %d %d %s", frame, W, H, table.concat(parts)))
+    end
+end
+print(string.format("avg frame total %.2f ms, of which render %.2f ms, uploads/frame %.2f", total / (NFRAMES - 10) * 1000, render_time / (NFRAMES - 10) * 1000, _G_UPLOADS / (NFRAMES - 10)))

tools/test/run.py

@@ -0,0 +1,115 @@
+#!/usr/bin/env python3
+"""Headless test harness: runs build/ImGui.luau + a main script in the Luau CLI against a mocked Roblox
+(roblox_mock.luau). Rebuilds the bundle first.
+
+  python3 tools/test/run.py                      # 400 frames of main.client.luau, scripted random input
+  python3 tools/test/run.py --open               # force every CollapsingHeader/TreeNode open (exercises whole demo)
+  python3 tools/test/run.py --big --open --bench # timing, best of 5
+  python3 tools/test/run.py --check              # incremental vs forced redraw must be pixel identical
+  python3 tools/test/run.py --png out.png        # screenshot of the last frame
+  python3 tools/test/run.py --main my_test.luau  # different LocalScript
+"""
+import argparse, os, shutil, subprocess, sys, zlib, struct, tempfile
+TMP = tempfile.mkdtemp(prefix="imgui_test_")  # per process: parallel runs must not share files
+
+HERE = os.path.dirname(os.path.abspath(__file__))
+ROOT = os.path.dirname(os.path.dirname(HERE))
+LUAU = shutil.which("luau") or "/nix/store/2m2ja613nndihc8qm10f2rhq6znp1nh4-luau-0.734/bin/luau"
+G = "game, workspace, Instance, Enum, Vector2, Vector3, UDim2, Color3, Content, warn, require, script, os"
+
+def build_run(args, flags):
+    subprocess.run([sys.executable, os.path.join(ROOT, "tools", "bundle.py"), TMP], check=True, stdout=subprocess.DEVNULL)
+    out = ["--!native", "--!optimize 2", flags, "local SOURCE_FNS = {}"]
+    def add(key, path):
+        s = "\n".join(l for l in open(path).read().split("\n") if not l.startswith("--!"))
+        out.append("SOURCE_FNS[%r] = function(%s)\n%s\nend" % (key, G, s))
+    add("ImGui.luau", os.path.join(TMP, "ImGui.luau"))
+    add("main.client.luau", args.main)
+    out.append(open(os.path.join(HERE, "roblox_mock.luau")).read())
+    global OFFSET, LAST_LINE
+    LAST_LINE = open(os.path.join(TMP, "ImGui.luau")).read().count("\n")
+    OFFSET = 5  # lines before the ImGui function body in run.luau (flags/header lines + "function(...)" line)
+    path = os.path.join(TMP, "run.luau")
+    open(path, "w").write("\n".join(out))
+    return path
+
+def run(args, extra=""):
+    flags = "ARG_FRAMES=%d; ARG_BIG=%s; ARG_OPEN=%s; %s" % (args.frames, str(args.big).lower(), str(args.open).lower(), extra)
+    try:
+        p = subprocess.run([LUAU, "-O2", "--codegen", build_run(args, flags)], capture_output=True, text=True, timeout=args.timeout)
+    except subprocess.TimeoutExpired as e:
+        return 124, "TIMEOUT (infinite loop?)\n" + remap((e.stdout or b"").decode(errors="replace"))
+    return p.returncode, remap(p.stdout + p.stderr)
+
+def remap(text):
+    """run.luau:N -> imgui/<file>.lua:M"""
+    import json, re
+    lm = json.load(open(os.path.join(TMP, "ImGui.linemap.json")))
+    def sub(m):
+        n = int(m.group(1)) - OFFSET  # line inside build/ImGui.luau (minus its 2 stripped --! lines)
+        n += 2
+        best = None
+        if n > LAST_LINE: return "<harness>:%d" % n
+        for start, name in lm:
+            if start <= n: best = (start, name)
+        if not best: return m.group(0)
+        return "%s:%d" % (best[1], n - best[0] + 1)
+    return re.sub(r"\S*run\.luau:(\d+)", sub, text)
+
+def images(out):
+    return [l.split() for l in out.split("\n") if l.startswith("IMG ")]
+
+def write_png(img, path, crop=None):
+    _, fr, w, h, hx = img; w, h = int(w), int(h); px = bytes.fromhex(hx)
+    W, H = crop or (w, h)
+    raw = bytearray()
+    for y in range(H):
+        raw.append(0)
+        for x in range(W):
+            o = (y * w + x) * 4; r, g, b, a = px[o:o + 4]; k = a / 255
+            raw += bytes([int(r * k + 90 * (1 - k)), int(g * k + 90 * (1 - k)), int(b * k + 90 * (1 - k))])
+    def chunk(t, d): return struct.pack('>I', len(d)) + t + d + struct.pack('>I', zlib.crc32(t + d) & 0xffffffff)
+    open(path, 'wb').write(b'\x89PNG\r\n\x1a\n' + chunk(b'IHDR', struct.pack('>IIBBBBB', W, H, 8, 2, 0, 0, 0))
+                           + chunk(b'IDAT', zlib.compress(bytes(raw))) + chunk(b'IEND', b''))
+
+def main():
+    ap = argparse.ArgumentParser()
+    ap.add_argument("--frames", type=int, default=400)
+    ap.add_argument("--main", default=os.path.join(ROOT, "main.client.luau"))
+    ap.add_argument("--big", action="store_true", help="demo window forced to 900x1000")
+    ap.add_argument("--open", action="store_true", help="force all CollapsingHeader/TreeNode open")
+    ap.add_argument("--bench", action="store_true")
+    ap.add_argument("--check", action="store_true")
+    ap.add_argument("--png")
+    ap.add_argument("--crop", default="1100x1080")
+    ap.add_argument("--timeout", type=int, default=120)
+    args = ap.parse_args()
+
+    if args.bench:
+        for mode in ["", "ARG_FORCE=true"]:
+            best = None
+            for _ in range(5):
+                code, out = run(args, mode)
+                if code: print(out[-3000:]); sys.exit(1)
+                line = [l for l in out.split("\n") if l.startswith("avg frame")][-1]
+                if best is None or float(line.split()[3]) < float(best.split()[3]): best = line
+            print("%-12s %s" % (mode or "incremental", best))
+        return
+    if args.check:
+        code, a = run(args, "ARG_DUMP=true")
+        code2, b = run(args, "ARG_DUMP=true; ARG_FORCE=true")
+        if code or code2: print((a if code else b)[-3000:]); sys.exit(1)
+        ok = [x[4] for x in images(a)] == [x[4] for x in images(b)]
+        print("PIXELS-IDENTICAL" if ok else "PIXELS-DIFFER"); sys.exit(0 if ok else 1)
+
+    code, out = run(args, "ARG_DUMP=true" if args.png else "")
+    print("\n".join(l if not l.startswith("IMG ") else l[:40] + "..." for l in out.split("\n"))[-4000:])
+    if args.png and images(out):
+        write_png(images(out)[-1], args.png, tuple(map(int, args.crop.split("x"))))
+        print("wrote", args.png)
+    sys.exit(code)
+
+try:
+    main()
+finally:
+    shutil.rmtree(TMP, ignore_errors=True)

tools/test/undefined.py

@@ -0,0 +1,40 @@
+#!/usr/bin/env python3
+"""Static check: ImGui.X / ImGui:X / global ImFoo() calls in imgui/*.lua that nothing defines.
+  python3 tools/test/undefined.py
+"""
+import os, re, collections
+ROOT = os.path.dirname(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+SRC = os.path.join(ROOT, "imgui")
+files = {}
+for dp, _, fn in os.walk(SRC):
+    for f in fn:
+        if f.endswith(".lua"):
+            files[os.path.relpath(os.path.join(dp, f), SRC)] = open(os.path.join(dp, f)).read()
+
+def strip(s):  # drop comments and strings (roughly) so we don't report text
+    s = re.sub(r"--\[(=*)\[.*?\]\1\]", "", s, flags=re.S)
+    s = re.sub(r"\[(=*)\[.*?\]\1\]", '""', s, flags=re.S)
+    s = re.sub(r'"(\\.|[^"\\\n])*"', '""', s)
+    s = re.sub(r"'(\\.|[^'\\\n])*'", "''", s)
+    return re.sub(r"--[^\n]*", "", s)
+
+defined_imgui, defined_global, used = set(), set(), collections.defaultdict(list)
+for name, src in files.items():
+    s = strip(src)
+    defined_imgui.update(re.findall(r"function\s+ImGui[.:](\w+)", s))
+    defined_imgui.update(re.findall(r"\bImGui\.(\w+)\s*=[^=]", s))
+    defined_global.update(re.findall(r"^\s*function\s+([A-Za-z_]\w*)\s*\(", s, re.M))
+    defined_global.update(re.findall(r"^\s*([A-Za-z_]\w*)\s*=[^=]", s, re.M))
+    defined_global.update(re.findall(r"^\s*local\s+function\s+([A-Za-z_]\w*)", s, re.M))
+    defined_global.update(re.findall(r"^\s*local\s+([A-Za-z_][\w, ]*)", s, re.M) and
+                          [x.strip() for l in re.findall(r"^\s*local\s+([A-Za-z_][\w, ]*)", s, re.M) for x in l.split(",")])
+    for i, line in enumerate(s.split("\n"), 1):
+        for m in re.findall(r"\bImGui\.(\w+)\s*\(", line):
+            used[("ImGui." + m, m, True)].append("%s:%d" % (name, i))
+        for m in re.findall(r"(?<![.:\w])(Im[A-Z]\w*)\s*\(", line):
+            used[(m, m, False)].append("%s:%d" % (name, i))
+
+missing = [(k, v) for k, v in used.items() if (k[1] not in defined_imgui if k[2] else k[1] not in defined_global)]
+for (full, _, _), locs in sorted(missing):
+    print("%-45s %d uses, e.g. %s" % (full, len(locs), ", ".join(locs[:3])))
+print("total undefined:", len(missing))