emscripten: testsprite rendering incorrectly in Chrome:

[icculus]

testsprite should look something like this (screenshot from Firefox, but desktops, phones, etc match this)...

...but on Chrome, it looks like this...

SDL_RenderClear() busted?

I can see from screenshots in #11949 that this has been broken for awhile. I'll try to bisect it.

[icculus]

release-3.2.0 has a black background. Maybe it's Emscripten 4.0 doing it? I'll try the older compiler.

[icculus]

It's not the clear color in general, because https://examples.libsdl.org/SDL3/renderer/01-clear/ works on Chrome.

[icculus]

SDL2's version of testsprite2 works in Chrome.

[icculus]

Okay, what the heck, SDL_RENDER_DRIVER=software is wrong on Chrome, too.

[icculus]

Okay, what the heck, software is wrong on Firefox, too!

[icculus]

Oh, we clear to alpha 0 in testsprite...

    /* Draw a gray background */
    SDL_SetRenderDrawColor(renderer, 0xA0, 0xA0, 0xA0, 0x00 /* used with --transparent */);
    SDL_RenderClear(renderer);

This produces different results than expected, but it might not be wrong...I assume most places are throwing the window framebuffer's alpha channel away.

[slouken]

Oh, this is probably related to bd680bd. We probably need to back at least part of it out. @ccawley2011 for visibility.

The right behavior would be to use RGBA for transparent windows and RGBX (and initialize the framebuffer) for normal windows.

[slouken]

Do you want me to throw together a quick proposed patch?

[icculus]

Sure, go for it. But bd680bd was 3 weeks ago, and 3.2.0 does this, so it predates that work.

[slouken]

Okay, I'll hold off until we better understand the issue here.