[Webkit-unassigned] [Bug 72965] [chromium] Use blending on opaque non-axis-aligned layers.

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=72965





--- Comment #4 from David Reveman <reveman at chromium.org>  2011-11-23 11:05:36 PST ---
(In reply to comment #3)
> (In reply to comment #2)
> > (In reply to comment #1)
> > > Created an attachment (id=116239)
 --> (https://bugs.webkit.org/attachment.cgi?id=116239&action=review) [details] [details] [details]
> > > Patch
> > 
> > You might want to take a look at Dave Reveman's comment on https://bugs.webkit.org/show_bug.cgi?id=70533 about making the axis-align (and pixel-aligned) test more consistent with what is used elsewhere in the compositor.
> > 
> > He recommends:
> > 
> > > This also needs to snap to the pixel grid to be correct. Instead of analyzing the transform, I think we should use the same logic as the anti-aliasing code, which is: 
> > > transformedQuad.isRectilinear() && transformedQuad.boundingBox().isExpressibleAsIntRect()
> 
> If an opaque rect is half inside a pixel, but axis aligned, would it want blending?

Yes, we need blending enabled whenever an anti-aliasing shader is used.

> 
> It would be possible to apply the layer's drawTransform() to its visibleLayerRect() and see if the resulting quad passes the above test.
> 
> @reveman would this be preferable?

Yes, have a look at:

http://trac.webkit.org/browser/trunk/Source/WebCore/platform/graphics/chromium/cc/CCTiledLayerImpl.cpp#L115

this is exactly what we're doing there.

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