[Webkit-unassigned] [Bug 48291] Fix LayoutTests/canvas/philip/tests/2d.composite.uncovered.fill.copy.html

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Fri Jun 24 14:09:23 PDT 2011


https://bugs.webkit.org/show_bug.cgi?id=48291


James Robinson <jamesr at chromium.org> changed:

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--- Comment #32 from James Robinson <jamesr at chromium.org>  2011-06-24 14:09:23 PST ---
(From update of attachment 97332)
View in context: https://bugs.webkit.org/attachment.cgi?id=97332&action=review

I'd be interesting in seeing perf comparisons that do not cover the entire canvas.  If the entire canvas is being copied then the clipOut() will exclude the whole canvas so that fill will be a no-op, so it's not surprising that performance is unaffected.  I'm also not sure about using clipOut for copy - it seems that for a path that isn't exactly on pixel boundaries this will cause issues with antialiasing.

If the clip region is small relative to the canvas, would it be more efficient to just clear the whole canvas without setting a clipOut at all before the actual draw?  On GPU implementations I could imagine this doing quite well.

This will change the pixel output for fast/canvas/canvas-composite.html, at least.  Could you update the pixel expectations for at least one platform so we can see that it's correct?

> Source/WebCore/html/canvas/CanvasRenderingContext2D.cpp:1514
> +    // As per the drawing model mentioned in http://www.whatwg.org/specs/web-apps/current-work/complete/the-canvas-element.html#drawing-model
> +    // We should display transparency for everywhere else for CompositeCopy, too

This comment does not seem useful, the comment on 1510 explains why we are displaying transparency elsewhere

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