ImGuiGML

A GameMaker demo project for the GMRT ImGUI compatibility module — a binding of Dear ImGui exposed to GML as a single global static class, ImGui.

The project is a live playground: one object, one room, and a Step event that exercises most of the API surface — windows, docking, tables, plots, drag & drop, draw lists, multi-select, custom TTF fonts and Unicode glyph ranges. It also ships a full API reference and the GML enum definitions you need to call the module.

Everything in this module is experimental and may change in future GMRT releases.

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Requirements

• GameMaker with the GMRT runtime (project built against IDE 2026.0.0.16).
• The ImGUI compatibility module available to the runtime. This repo contains no extension — ImGui is resolved by GMRT itself, not by an asset in the project tree.

Running it

1. Open ImGuiGML.yyp in the GameMaker IDE.
2. Select a GMRT target and run.
3. Room1 spawns a single Object1, which draws the whole demo from its Step event.

There is nothing to configure. The window is 1366×768 with docking enabled by default (global.enable_docking in Object1's Create event).

Project layout

Path	What it is
objects/Object1/Create_0.gml	Demo state, font loading, glyph ranges, and all ImGui* enum definitions
objects/Object1/Step_0.gml	The demo UI itself — every widget call lives here
scripts/Script1/Script1.gml	GM-side helper constructors: ImColor, ImGuiWindowClass, ImGuiSelectionBasicStorage
notes/ImGui_API.md/ImGui_API.md.txt	Full API reference — ~2400 lines of signatures, per-argument notes, and the enums
datafiles/fonts/	Noto Sans (Main + Hiragana Bold) and Roboto, plus their Apache-2.0 licence
sprites/	spr_example, spr_example2 — used for Image, ImageButton, and draw-list image calls

Quick start

Every function is static on the ImGui class, so you call it directly. UI is built imperatively each frame from a Step event:

/// Step Event
if (ImGui.Begin("Hello", { open: true })) {
    ImGui.Text("ImGui version: " + ImGui.GetVersion());

    if (ImGui.Button("Click me")) {
        show_message_async("clicked");
    }

    my_slider = ImGui.SliderInt("Amount", my_slider, 0, 10);
}
ImGui.End();

Two conventions are worth knowing up front:

• State structs. Widgets that need to write state back to you take a struct, e.g. ImGui.Begin("Name", { open: true }) — ImGui flips open to false when the user clicks the close button.
• Value returns. Sliders and inputs return their new value rather than mutating in place: val = ImGui.SliderFloat("x", val, 0, 1). Array variants (SliderInt4, InputFloat4, …) write into the array you pass.

British and American spellings (Colour / Color) are aliases for the same native function.

Enums

The GML enum definitions live in the #region Enums block at the bottom of Object1's Create event, and again at the end of the API reference. Copy that block into your own project — ImGuiWindowFlags, ImGuiTableFlags, ImGuiCol, ImGuiStyleVar, ImDrawFlags, and the rest are plain GML enums, not something the module provides.

Helper constructors

scripts/Script1/Script1.gml supplies the GM-side structs the module expects:

// Colours for the *4 colour editors and pickers
var c = new ImColor(c_aqua, 0.5);      // GM colour + alpha
var d = new ImColor(128, 255, 255);    // r, g, b
ImGui.ColorPicker4s("Pick", c);
c.Color();  // BGR int, for GM drawing functions
c.Alpha();

// Multi-select storage — remember to Destroy() it
var sel = new ImGuiSelectionBasicStorage();
sel.ApplyRequests(ImGui.BeginMultiSelect(flags, sel.GetSize(), count));
sel.Contains(index);
sel.Destroy();

ImGuiWindowClass is also defined here for the window-class/viewport calls.

What the demo covers

Text and layout · buttons (regular, small, invisible, arrow, colour) · images, image buttons and GameMaker surfaces rendered into ImGui · tree nodes and collapsing headers · sliders and drag widgets · text/int/float inputs, multiline and hint variants · colour pickers and editors · tables with per-cell background colours · tab bars · line and histogram plots · dock spaces and the DockBuilder API (programmatic split layout) · drag & drop with copy/move/swap modes · TTF font loading with Cyrillic and Japanese glyph ranges · draw lists (text, circles, béziers, rounded images, n-gons) · the multi-select system with box-select and keyboard navigation · the built-in ShowDemoWindow.

Notes and caveats

• Fonts are included files under datafiles/fonts/ and are loaded at runtime from assets/fonts/…. Only NotoSans-Main.ttf is loaded by the demo; Roboto and the Hiragana Bold face are there for you to experiment with.
• Arabic text renders, but BIDI ordering and letter joining are not handled — see str_marhaba in the Create event.
• static_get(ImGui) is used to peek at module internals and is guarded in a try/catch; older runtimes without it show a disabled field and a warning tooltip instead.
• *.resource_order and the GMRT Build directory are gitignored; .yy files are marked linguist-generated and forced to LF.

Credits

• Dear ImGui by Omar Cornut.
• The demo layout is adapted from knno/ImGM which was heavily inspired and based on Nommiin's ImGui_GM;
• The DockBuilder setup follows this gist by Aidan Sun.
• Bundled fonts (Noto Sans, Roboto) are licensed under Apache-2.0 — see datafiles/fonts/LICENSE.txt.