[Webkit-unassigned] [Bug 48294] Fix LayoutTests/canvas/philip/tests/2d.composite.uncovered.fill.source-in.html

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=48294


Carol Szabo <carol.szabo at nokia.com> changed:

           What    |Removed                     |Added
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             Status|UNCONFIRMED                 |ASSIGNED
         AssignedTo|webkit-unassigned at lists.web |carol.szabo at nokia.com
                   |kit.org                     |
                 CC|                            |carol.szabo at nokia.com
     Ever Confirmed|0                           |1




--- Comment #1 from Carol Szabo <carol.szabo at nokia.com>  2010-12-20 16:19:03 PST ---
I will try to resolve this bug.
But fist I want to make sure that I am on the right track.
I believe that either Philip made an error when setting up this test or may not have a correct interpretation of the standard.
The test verifies that when the globalCompositingOperation is source-in, a fillRect operation clears all the canvas except for the area being filled.
After talking to several people, my belief is that this test is not correct. The compositing operation applies only to pixels that are being composited, that is the pixels that are covered by the fill in this case, thus pixels not covered by the fill should not be touched. I see a difference between one of the pixels being composited to generate a result being transparent and yielding a transparent result and a pixel not being the result of a compositing operation as there is no corresponding source or destination pixel.

By my interpretation the current WebKit behavior is correct. It is the expected result that is not.
By extending the interpretation that is consistent with the current expected result of the test, to source-out or copy, it would mean that if one fills an area outside the bounds of a canvas with a color, the canvas should be extended to show the color in that area, which I again find not to be what the standard designer intended.

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