Bug 44573 – [chromium] Implement clipping for composited layers

• Component: WebCore Misc.
• Status: RESOLVED FIXED

[Vangelis Kokkevis]

The accelerated compositor in chromium doesn't yet handle layers that clip their descendants.

[Vangelis Kokkevis]

Created attachment 65359 [details]
Proposed patch

[Vangelis Kokkevis]

Created attachment 65436 [details]
Proposed patch - removed temporary stencil clipping debug code

[Kenneth Russell]

Comment on attachment 65436 [details]
Proposed patch - removed temporary stencil clipping debug code

Generally looks good. There's one piece of complexity below I'd ask you to rethink, but you can fix the issues below before commit.

WebCore/platform/graphics/chromium/LayerChromium.cpp:456
 +      GLC(glUniform4f(sv->borderShaderColorLocation(), 0, 1 , 0, 0.7));
It's probably worth a comment that the color values don't matter here since the color mask is set to all false at this point.

WebCore/platform/graphics/chromium/LayerRendererChromium.cpp:506
 +              // will allow us up to 255 nested clipping layers which is hopefuly enough.
hopefully

WebCore/platform/graphics/chromium/LayerRendererChromium.cpp:554
 +              ASSERT(!currentStencilValue);
Because of this ASSERT, it feels to me like there must be some simpler logic just involving a test of "--currentStencilValue == 0" or similar, and getting rid of mustDisableStencil and stencilTestEnabledForSubtree. I'm not 100% sure of this though and don't want you to risk breaking your current logic if it's well tested, so feel free to just consider this for the future.

[Vangelis Kokkevis]

Committed r66114: <http://trac.webkit.org/changeset/66114>