[Webkit-unassigned] [Bug 39177] New: Canvas 2d globalCompositeOperation source-in, source-out, destination-in, destination-atop, darker and copy are broken

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=39177

           Summary: Canvas 2d globalCompositeOperation source-in,
                    source-out, destination-in, destination-atop, darker
                    and copy are broken
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: All
               URL: https://developer.mozilla.org/samples/canvas-tutorial/
                    6_1_canvas_composite.html
        OS/Version: All
            Status: UNCONFIRMED
          Severity: Normal
          Priority: P2
         Component: Layout and Rendering
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: stefanwehrmeyer at gmail.com


Created an attachment (id=56188)
 --> (https://bugs.webkit.org/attachment.cgi?id=56188)
reference rendering with wrong renderings marked red 

What steps will reproduce the problem?
1. Compare the canvas rendering of
https://developer.mozilla.org/samples/canvas-tutorial/6_1_canvas_composite.html 
to the reference images at 
https://developer.mozilla.org/en/Canvas_tutorial/Compositing

What goes wrong?
The following composite operations do not render as they should, but as the following:
"source-in" renders like "source-atop"
"source-out" renders like "xor"
"destination-in" renders like there was no second drawing (no red circle)
"destination-atop" renders like "destination-over"
"darker" doesn't look like the reference (not sure though if the reference gets the darker color right)
"copy" renders like "source-over"

A reference rendering is attached with buggy compositing operations marked red.

This bug is related to
https://bugs.webkit.org/show_bug.cgi?id=34027
but this is a more complete version of the current canvas compositing bugs.

This bug has also been filed downstream at
http://code.google.com/p/chromium/issues/detail?id=37799

Firefox and Opera currently get most composite operations right. This should be fixed as soon as possible, so developers don't have to write custom code for webkit.

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