Bug 79949

Summary: Semi-transparent image translated over a negative-scaled image produces painting artifacts
Product: WebKit Reporter: Tab Atkins <tabatkins>
Component: CSSAssignee: Nobody <webkit-unassigned>
Status: NEW    
Severity: Normal CC: bfulgham
Priority: P2 Keywords: DoNotImportToRadar
Version: 528+ (Nightly build)   
Hardware: Unspecified   
OS: Unspecified   
URL: http://code.google.com/p/chromium/issues/detail?id=109067

Tab Atkins
Reported 2012-02-29 14:38:28 PST
Steps to reproduce: 1. Create a page with two images overlaid atop each other. The upper image must be semi-transparent; the lower image doesn't matter. 2. Transform the lower image with a negative-scale transform, like "scale(-1)". 3. Translate the upper image across the lower image, with an animation or manually. Effect: As the upper image is translated across the lower image, it leaves behind "trails" of pixels on the lower image. This bug only appears to happen when the lower image is transformed as described. Any other transform doesn't trigger the issue. Reduced testcase and screenshot of problem located at the original bug in the Chromium bug tracker: <http://code.google.com/p/chromium/issues/detail?id=109067> The Chromium bug states that this bug happens on Windows, but not Mac. I can confirm that it also occurs on Linux.
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