Roblox backend: one layer (Frame + tiles) per draw list so moving windows costs no redraw; gradient rect fast path; t_drag/t_composite checks

2026-10-08 11:10:53 -05:00
parent 71843392f1
commit ceb66d3067
7 changed files with 564 additions and 190 deletions
@@ -0,0 +1,77 @@
+-- Composites every visible tile ImageLabel (walking the ScreenGui like Roblox: ZIndex order, nested offsets) onto a
+-- black screen and prints the RGB of a region as hex rows ("ROW y hex"). Compare two backend versions with
+-- tools/test/compare_composite.py to prove a backend change renders the same pixels.
+local G = require(game:GetService("ReplicatedStorage"):WaitForChild("ImGui"))
+local ImGui, ImVec2, ImVec4 = G.ImGui, G.ImVec2, G.ImVec4
+ImGui.CreateContext()
+G.ImGui_ImplRoblox.Init()
+G.ImGui_ImplRoblox.SetRenderRate(0)
+local io = ImGui.GetIO()
+local col = ImVec4(0.4, 0.7, 0.2, 0.5)
+local W, H = 1280, 760
+local frame = 0
+
+local function composite(gui)
+    local screen = buffer.create(W * H * 3)
+    local function walk(inst, ox, oy)
+        local kids = inst:GetChildren()
+        table.sort(kids, function(a, b) return (a.ZIndex or 1) < (b.ZIndex or 1) end) -- table.sort isn't stable, but siblings with equal ZIndex never overlap here
+        for _, c in ipairs(kids) do
+            if c.Visible ~= false then
+                local x, y = ox + (c.Position and c.Position.X or 0), oy + (c.Position and c.Position.Y or 0)
+                if c.ClassName == "ImageLabel" then
+                    local img = c.ImageContent.Object
+                    local px, sz = img.Pixels, img.Size.X
+                    for ty = 0, sz - 1 do
+                        local sy = y + ty
+                        if sy >= 0 and sy < H then
+                            for tx = 0, sz - 1 do
+                                local sx = x + tx
+                                if sx >= 0 and sx < W then
+                                    local o = (ty * sz + tx) * 4
+                                    local a = buffer.readu8(px, o + 3)
+                                    if a > 0 then
+                                        local d = (sy * W + sx) * 3
+                                        local fa = a / 255
+                                        for ch = 0, 2 do
+                                            local v = buffer.readu8(px, o + ch) * fa + buffer.readu8(screen, d + ch) * (1 - fa)
+                                            buffer.writeu8(screen, d + ch, math.floor(v + 0.5))
+                                        end
+                                    end
+                                end
+                            end
+                        end
+                    end
+                end
+                walk(c, x, y)
+            end
+        end
+    end
+    walk(gui, 0, 0)
+    return screen
+end
+
+game:GetService("RunService").Stepped:Connect(function()
+    frame += 1
+    G.ImGui_ImplRoblox.NewFrame()
+    io.DeltaTime = 1 / 60
+    io:AddMousePosEvent(300 + (frame * 37) % 300, 100 + (frame * 53) % 500)
+    ImGui.NewFrame()
+    ImGui.ShowDemoWindow(true)
+    ImGui.SetNextWindowPos(ImVec2(20, 20)); ImGui.SetNextWindowSize(ImVec2(600, 700))
+    ImGui.Begin("Pickers")
+    ImGui.ColorPicker4("bar", col, G.ImGuiColorEditFlags.PickerHueBar)
+    ImGui.ColorPicker4("wheel", col, G.ImGuiColorEditFlags.PickerHueWheel)
+    ImGui.End()
+    ImGui.Render()
+    G.ImGui_ImplRoblox.RenderDrawData(ImGui.GetDrawData())
+    if frame == ARG_FRAMES - 1 then
+        local gui = game:GetService("Players").LocalPlayer.PlayerGui:FindFirstChild("ImGui")
+        local screen = composite(gui)
+        for y = 0, H - 1 do
+            local t = table.create(W * 3)
+            for i = 0, W * 3 - 1 do t[i + 1] = string.format("%02x", buffer.readu8(screen, y * W * 3 + i)) end
+            print("ROW", y, table.concat(t))
+        end
+    end
+end)
@@ -0,0 +1,43 @@
+-- Benchmark: drags the demo window (real mouse drag on its title bar) and keeps a color picker window open.
+-- Watch "render" ms and uploads/frame: with per-window layers, dragging should upload ~nothing.
+local G = require(game:GetService("ReplicatedStorage"):WaitForChild("ImGui"))
+local ImGui, ImVec2, ImVec4 = G.ImGui, G.ImVec2, G.ImVec4
+ImGui.CreateContext()
+G.ImGui_ImplRoblox.Init()
+G.ImGui_ImplRoblox.SetRenderRate(0)
+local io = ImGui.GetIO()
+local col = ImVec4(0.4, 0.7, 0.2, 0.5)
+local frame = 0
+local bx, by = 0, 0
+local MODE = ARG_OPEN == true and "picker" or "drag"
+game:GetService("RunService").Stepped:Connect(function()
+    frame += 1
+    G.ImGui_ImplRoblox.NewFrame()
+    io.DeltaTime = 1 / 60
+    if MODE == "drag" then
+        local t = math.abs((frame % 200) - 100) -- triangle wave, smooth back and forth
+        if frame == 5 then local w = ImGui.FindWindowByName("ImGui Sincerely Demo"); bx, by = w.Pos.x + 80, w.Pos.y + 8; io:AddMousePosEvent(bx, by) elseif frame == 6 then io:AddMouseButtonEvent(0, true)
+        elseif frame > 6 then io:AddMousePosEvent(bx - t * 5, by + t * 2) end
+    else
+        io:AddMousePosEvent(60 + (frame * 7) % 200, 80 + (frame * 5) % 200)
+        if frame == 6 then io:AddMouseButtonEvent(0, true) end
+    end
+    ImGui.NewFrame()
+    if MODE == "drag" then
+        if frame < 3 then ImGui.SetNextWindowPos(ImVec2(20, 20)); ImGui.SetNextWindowSize(ImVec2(500, 650)) end
+        ImGui.ShowDemoWindow(true)
+    else
+        ImGui.SetNextWindowPos(ImVec2(20, 20)); ImGui.SetNextWindowSize(ImVec2(700, 700))
+        ImGui.Begin("Pickers")
+        ImGui.ColorPicker4("bar", col, G.ImGuiColorEditFlags.PickerHueBar)
+        ImGui.ColorPicker4("wheel", col, G.ImGuiColorEditFlags.PickerHueWheel)
+        ImGui.End()
+    end
+    ImGui.Render()
+    G.ImGui_ImplRoblox.RenderDrawData(ImGui.GetDrawData())
+    if frame == ARG_FRAMES - 1 and MODE == "drag" then
+        local w = ImGui.FindWindowByName("ImGui Sincerely Demo")
+        assert(w.Pos.y > 25, "window was not dragged")
+        print("DRAG OK", w.Pos.x, w.Pos.y, w.Collapsed, ImGui.GetDrawData().TotalVtxCount)
+    end
+end)