feat(emscripten): Add SDL_SetWindowIcon implementation.

[ej-sanmartin]

Description

Implements SDL_SetWindowIcon for Emscripten by converting the icon surface to a PNG data URL using the Canvas API. Chose PNG for universal browser support and smaller file sizes, and used Canvas for the conversion since it's the standard browser API for handling pixel data with built-in format conversion and encoding.

Existing Issue(s)

Fixes #14478

Testing

• Builds successfully on MacOS 12.7.6
• Test with a simple script, which uses this method and updates the favicon on the browser to a red square.

Screenshot:

Script:

#include <SDL3/SDL.h>
#include <emscripten.h>

int main(int argc, char* argv[])
{
    if (!SDL_Init(SDL_INIT_VIDEO)) {
        SDL_Log("SDL_Init failed: %s", SDL_GetError());
        return 1;
    }

    SDL_Window* window = SDL_CreateWindow("Icon Test", 640, 480, 0);
    if (!window) {
        SDL_Log("SDL_CreateWindow failed: %s", SDL_GetError());
        SDL_Quit();
        return 1;
    }

    // Create a 32x32 red surface
    SDL_Surface* icon = SDL_CreateSurface(32, 32, SDL_PIXELFORMAT_RGBA32);
    if (!icon) {
        SDL_Log("SDL_CreateSurface failed: %s", SDL_GetError());
        SDL_DestroyWindow(window);
        SDL_Quit();
        return 1;
    }

    // Fill with bright red
    SDL_FillSurfaceRect(icon, NULL, SDL_MapSurfaceRGBA(icon, 255, 0, 0, 255));

    // Test SDL_SetWindowIcon - should change favicon to red square
    SDL_Log("Setting window icon...");
    if (SDL_SetWindowIcon(window, icon)) {
        SDL_Log("SUCCESS!");
    } else {
        SDL_Log("FAILED!",
                SDL_GetError());
    }

    SDL_DestroySurface(icon);
    SDL_DestroyWindow(window);
    SDL_Quit();
    return 0;
}

[ej-sanmartin]

OpenBSD Build Failure seems unrelated to my change:

Error Log shows this:

Can't install python-3.12.11 because of libraries
|library c.102.0 not found
| /usr/lib/libc.so.100.3 (system): bad major

[slouken]

Does it help that SDL supports PNG natively now? You can use SDL_SavePNG_IO() with a dynamic memory stream to encode it if you want.

[ej-sanmartin]

I'll check out that approach, I'll send out another commit later today.

[ej-sanmartin]

Looking into this, yes SDL_SavePNG_IO() is a lot more robust and I see I can use SDL_IOFromDynamicMem() as dynamic memory stream for PNG encoding. I'll work on this and test/build locally.

[ej-sanmartin]

Updated, builds successfully! SDL_SavePNG_IO() is a lot better.

[slouken]

Looks good! Merged, thanks!

[icculus]

Thanks for jumping on this one, @ej-sanmartin! Looks great!

[ej-sanmartin]

You're welcome, happy to help!