Dear ImGui for Roblox - not yet ported / known gaps
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Upstream reference: tools/test/upstream/ (ocornut/imgui docking branch, 1.93 WIP).
Re-check with: python3 tools/test/missing.py [imgui|widgets|tables|draw]  and  python3 tools/test/undefined.py --no-demo
(missing.py also lists names the port defines differently, e.g. the *V printf variants and DragFloat2..4 / DragInt2..4,
which exist as ImGui.DragFloat2 = DragFloatN(2) etc. Those are NOT gaps.)


FEATURES NOT PORTED
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- Multi-select / box-select: BeginMultiSelect, EndMultiSelect, MultiSelectItemHeader/Footer, MultiSelectAddSetAll,
  MultiSelectAddSetRange, SetNextItemSelectionUserData, BeginBoxSelect/EndBoxSelect, DebugNodeMultiSelectState.
  (Selectable/TreeNode call sites are stubbed with TODOs; the demo "Selection State & Multi-Select" section is not ported.)
- Typing-select (type to jump in lists): GetTypingSelectRequest, TypingSelectFind*, DebugNodeTypingSelectState.
- Examples > Assets Browser (needs multi-select + box-select).
- Metrics > Tools > Item Picker (UpdateDebugToolItemPicker).
- DebugFlashStyleColor / UpdateDebugToolFlashStyleColor (Style Editor "?" flash button).
- DebugNodeInputTextState (Metrics > Internal state > InputText).
- BringWindowToDisplayBehind: stub, does nothing.
- ColorEdit4 / ColorPicker4: drag & drop target (dropping a color onto a color widget).
- ImFontAtlas:AddFontFromMemoryCompressedTTF: stub (binary_to_compressed_c fonts can't be loaded).
- ImGuiSizeCallbackData: SetNextWindowSizeConstraints custom callbacks only partially supported
  (Examples > Constrained Resize).
- LogSetNextTextDecoration (Selectable "[ ]" decoration in log/clipboard output).
- stb_truetype: cmap high-byte mapping (some CJK fonts assert).
- Context hooks removal (RemoveContextHook), SetContextName.
- RegisterUserTexture / UnregisterUserTexture.
- ErrorCheckNewFrameSanityChecks / ErrorCheckEndFrameSanityChecks (fewer usage-error asserts than upstream).
- GetAllocatorFunctions (n/a in Luau).

WON'T DO (platform)
-------------------
- Multi-viewports / platform windows: Roblox has one window. Viewport API exists for the main viewport only.
- Gamepad navigation via a real gamepad backend (keyboard navigation works).
- IME / non-ASCII keyboard text input (backend sends printable ASCII only).

NOT VERIFIED LINE BY LINE AGAINST UPSTREAM
------------------------------------------
- Demo: Layout & Scrolling, Popups & Modal windows, Inputs & Focus.

KNOWN ISSUES
------------
- Tables > "Columns flags": disabling every column asserts in TableUpdateLayout (upstream asserts too).
- Style Editor > Colors uses a ListClipper (port-only change, upstream submits every row).

PERFORMANCE IDEAS (not done)
----------------------------
- Opt-in cached windows (skip user code for idle windows).
- Cheaper visible ColorEdit4 rows; cheaper Begin() for child windows.

PLANNED EXTENSIONS
------------------
- ImGuizmo, ImNodes, ImGuiColorTextEdit, ImPlot, ImPlot3D (as separate extensions/, built with a --with flag).