Emscripten

allegro-ts-emscripten is a complete C header mapping of allegro-ts that lets you compile Allegro 4 C/C++ games to WebAssembly and run them in the browser, using allegro-ts as the backend runtime.

• GitHub
• Live Examples

How it works

allegro-ts-emscripten provides a set of C headers that declare all Allegro 4 functions. The implementations call into allegro-ts via Emscripten's JavaScript interop layer. This means your existing Allegro 4 C code compiles with emcc just as it would with GCC, and allegro-ts handles all the actual rendering, input, and audio in the browser.

C source ──emcc──▶ WebAssembly ──Emscripten──▶ allegro-ts ──▶ HTML5 Canvas

Prerequisites

• Emscripten SDK installed and activated (emsdk activate latest)
• CMake ≥ 3.10
• Make (or Ninja)
• Node.js (for serving the output)

Setup

Clone the repository and initialise the allegro-ts submodule:

git clone https://github.com/alegemaate/allegro-ts-emscripten.git
cd allegro-ts-emscripten

Run the setup script to produce a flattened copy of the allegro-ts library that Emscripten can consume:

./setup.sh

This generates the C headers and JS glue into a lib/ directory that the CMake build picks up automatically.

Building the examples

cd examples
emcmake cmake -G "Unix Makefiles" .
make

Replace "Unix Makefiles" with "Ninja" if you prefer Ninja.

The compiled output (.html, .js, .wasm) lands in examples/build/.

Running locally

WebAssembly files must be served over HTTP — opening them via file:// will not work. Use any static file server:

npm i -g serve
cd examples/build
serve

Then open http://localhost:3000 in your browser and navigate to any example.

Examples

Seven demos are included and hosted live:

Example	Description
colortest	Color palette and makecol
exaccel	Bitmap acceleration
exbmp	Bitmap loading and drawing
exbounce	Sprite movement and collision
exflip	Page flipping / double buffering
exprimitives	Lines, rects, circles
exstress	Stress test / performance

Writing your own game

Create a .c file that includes the Allegro 4 headers and add it to the CMakeLists. The setup script places the flattened headers in lib/, so your include path just needs to point there:

#include "allegro.h"

int main(void) {
    allegro_init();
    set_gfx_mode(GFX_AUTODETECT_WINDOWED, 640, 480, 0, 0);
    install_keyboard();

    while (!key[KEY_ESC]) {
        clear_to_color(screen, makecol(0, 0, 0));
        textout_ex(screen, font, "Hello, browser!", 10, 10, makecol(255, 255, 255), -1);
        rest(16);
    }

    return 0;
}

Compile with:

emcc main.c -I../lib -o build/main.html

TIP

Use rest(16) instead of a busy loop to yield control back to the browser event loop. The Emscripten runtime maps rest to a non-blocking async sleep.

Limitations

• Allegro 4 functions that have no browser equivalent (e.g. set_window_title) are stubs that do nothing.
• File I/O uses Emscripten's virtual filesystem — bundle assets using --preload-file or --embed-file at compile time.
• MIDI playback relies on allegro-ts's built-in General MIDI player, which may differ from native MIDI output.