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Shaun Wild edited this page Sep 17, 2026 · 24 revisions

ComposeGL

These docs are for ComposeGL 0.6.0. New since 0.5.0: What's new in 0.6.0.

A UI toolkit for games, built on androidx.compose.runtime and nothing else.

Try it in your browser: the showcase — click, type or pick up a pad and go round every widget, layout, animation and effect, live.

You write Text("Score: $score"). It is drawn with OpenGL, through your engine, inside your game loop — no separate window, no web view, no second thread, no Android dependency.

Box(Modifier.fillMaxSize()) {
    Panel(Modifier.align(Alignment.BottomStart).padding(28f).width(280f)) {
        Column(verticalArrangement = Arrangement.spacedBy(10f)) {
            Text("HULL")
            Bar(hull, Modifier.fillMaxWidth())
            Row(Modifier.fillMaxWidth(), horizontalArrangement = Arrangement.SpaceBetween) {
                Text("AMMO")
                Text("$ammo")
            }
        }
    }
    Reticle(reticle, Modifier.align(Alignment.Centre))
}

a heads-up display: a hull bar and an ammo count in the corner, a crosshair in the middle

Every picture on this wiki is a photograph of the real toolkit, taken by ./gradlew :composegl-demo:docShots — never a drawing of it.

Start here
Your first screen a window, a panel and a working button, in about eighty lines
Layout Column, Row, Box, FlowRow, Grid, lazy lists and grids, weight, and what differs from Compose
Modifiers the full list, and the three rules that are ours
Widgets everything that ships in the toolkit: text, buttons, fields, collapsing headers, splitters, spinners, colour pickers, lists, tables, tooltips
Game widgets the game tier, in composegl-game: bars, reticle, hit markers, damage direction arcs, a low-health vignette, damage numbers, world markers, cooldowns, hotbar, weapon wheel, inventory grid, minimap, compass bar, dialogue, chat, objective tracker, subtitles, skill trees, item cards, particles
Animation clocks, springs, panels that animate in and out, screens that crossfade or slide, and pausing it all to look

Then
Skins one JSON file holds every colour in your game, and hot reloads
Input mouse, keyboard, pad, focus, and giving the world what the interface did not want
Saving state the tab, the scroll position and the half-typed name, still there when a screen comes back
Split-screen local co-op: a HUD per player, and each pad routed to its own player
Localisation strings by language, screens that mirror for Arabic and Hebrew, and Hebrew and English on one line
Shaders blur, outline, dissolve — and your own GLSL bound to any widget
Backends LibGDX, raw OpenGL, a browser tab, Android, and writing your own
Scene view a panel with your own 3D scene inside it: a level editor viewport, a model preview, a picture-in-picture camera
Render targets drawing into a texture instead of the window: a panel in the world, or your own 3D scene with a depth buffer
KorGE a screen on a KorGE stage: fonts, skins, input, split-screen, in-world panels, testing, and the limits
Kool a screen as a Kool scene on the desktop and Android: the mouse and touch, Kool textures, a scene view with Kool's GL state kept true, and the limits
Testing a whole interface tested with no window and no GPU, and @Preview composables drawn to PNGs
Live previews every @Preview in a window, compiled and redrawn when you save a file, from composegl-preview
Debugging floating windows that tune your own values while the game runs and dock to an edge or tab together when there are a few, overlays for layout, focus, overdraw, draw calls, redraws and text, an inspector, a browsable tree of the whole screen, live plots, and a drop-down console for typing commands, from composegl-debug
Custom layouts writing your own MeasurePolicy when the three are not enough

What it is not

  • Not Material. No theme to fight, no component library to override. Widgets take their look from a skin file.
  • Not androidx.compose.ui. No dp, no Modifier.Node, no density. Sizes are floats against a design resolution; the viewport does the rest.
  • Not tied to an engine. LibGDX and KorGE are optional modules. The core names no engine anywhere, and the build fails if anybody adds one.

What it is for

Games. A HUD that costs nothing while it is standing still, bars with a damage trail, a crosshair with spread and hit markers, damage numbers and nameplates anchored in the world, pad navigation that works without being wired up, prompts that change the moment somebody picks up a controller, and a text size setting that makes the words bigger without making the whole interface bigger.

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