[Webkit-unassigned] [Bug 178705] [WPE] Two WebGL layout tests are failing

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Mon Apr 9 21:29:25 PDT 2018


https://bugs.webkit.org/show_bug.cgi?id=178705

--- Comment #1 from Carlos Eduardo Ramalho <cadubentzen at gmail.com> ---
fast/canvas/webgl/tex-image-and-sub-image-2d-with-video.html is passing since r225060 (see bug 180000).

About webgl/1.0.2/conformance/rendering/multisample-corruption.html, the bug happens because antialiasing is disabled for GLES2 (check GraphicsContext3D::validateAttributes() in GraphicsContext3DOpenGLES.cpp)

In order to enable it, one of these extensions would be required, since according to the specification GLES2 does not support multisampling in framebuffer objects:
- APPLE_framebuffer_multisample, which is what Apple used enclosed in #if's, or
- ANGLE_framebuffer_multisample, which is implemented in ANGLE translating it OpenGL extensions calls or
- other vendor-specific extensions

So right now GraphicsContext3D::resolveMultisamplingIfNecessary() for GLES is empty and I don't know how exactly to implement it without non vendor-specific GLES2 extensions. GLES3 on the other hand does support multisampling in framebuffer objects.

The test can be run manually from here: https://www.khronos.org/registry/webgl/sdk/tests/conformance/rendering/multisample-corruption.html

By the way, WebKit-based browsers (GTK and Safari) seem to make the red canvas in the test disappear or turn black, which does not seem like a correct behavior although the pixel reading values still returns correct. I could not trace to exactly why it happens but Chrome and Firefox display correctly. Disabling accelerated compositing make WebKitGTK+ to work OK.

Please correct me if I made wrong conclusions in the above investigation.

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