Bug 314719 – [WPE][GTK] Atlas textures use spec-violating glTexImage2D(internal=GL_RGBA, format=GL_BGRA), render black on strict GLES drivers

• Status: RESOLVED
• Resolution: FIXED
• Component: New Bugs

[Alejandro G. Castro]

SkiaGPUAtlas allocates BitmapTextures with the UseBGRALayout flag, which is meant to give them BGRA storage. BitmapTexture::allocateTexture() and BitmapTexture::reset() currently call:

      glTexImage2D(target, 0, GL_RGBA, w, h, 0, textureFormat(), UNSIGNED_BYTE, nullptr);

where textureFormat() returns GL_BGRA for UseBGRALayout textures. So the actual call for atlas textures is:

      glTexImage2D(target, 0, GL_RGBA, w, h, 0, GL_BGRA, UNSIGNED_BYTE, nullptr);

This combination is undefined per the EXT_texture_format_BGRA8888 spec, which mandates internalFormat == format == GL_BGRA_EXT:

      https://registry.khronos.org/OpenGL/extensions/EXT/EXT_texture_format_BGRA8888.txt

Driver behaviour observed:

    * Mesa (Intel/AMD/llvmpipe): permissive — accepts the call. Downstream rendering happens to come out correct because TextureMapper's shaders swizzle BGRA→RGBA at sample time.

    * Adreno (Pixel 7, Android arm64): strict — rejects every upload with GL_INVALID_OPERATION (0x502). Confirmed by glGetError() instrumentation: 100% of atlas uploads fail. The texture is left in undefined state, and SkImages::BorrowTextureFrom(..., kRGBA_8888_SkColorType, ...) reading from undefined storage renders solid black on subsequent FALLBACK direct-draws.

[Alejandro G. Castro]

Pull request: https://github.com/WebKit/WebKit/pull/64834

[EWS]

Committed 313395@main (b47541a2e001): <https://commits.webkit.org/313395@main>

Reviewed commits have been landed. Closing PR #64834 and removing active labels.

[Radar WebKit Bug Importer]

<rdar://problem/177318630>

[WebKit Commit Bot]

Re-opened since this is blocked by bug 315035

[Alejandro G. Castro]

Pull request: https://github.com/WebKit/WebKit/pull/65193

[EWS]

Committed 313653@main (1f31db09ec64): <https://commits.webkit.org/313653@main>

Reviewed commits have been landed. Closing PR #65193 and removing active labels.