Bug 126262

Summary: Graphics buffer issue with clip-path and fixed positioned element
Product: WebKit Reporter: Dirk Schulze <krit>
Component: CSSAssignee: Simon Fraser (smfr) <simon.fraser>
Severity: Normal CC: commit-queue, dino, esprehn+autocc, glenn, kondapallykalyan, rniwa, simon.fraser, webkit-bug-importer
Priority: P2 Keywords: InRadar
Version: 528+ (Nightly build)   
Hardware: Unspecified   
OS: Unspecified   
Bug Depends on:    
Bug Blocks: 126207    
Description Flags
Patch thorton: review+

Description Dirk Schulze 2013-12-27 07:07:58 PST
Created attachment 220059 [details]

In the attached example there is a small example where a fixed positioned element is clipped with the clip-path property. It seems like the fixed positioned element is drawn on a graphics buffer and this buffer is not cleared. This leads to artifacts on areas that are clipped away.

Reload the example multiple times to see the issue. In Safari stable the background is always black. In nightlies the background is not stable. It even happened that a video playing in another application show through.

This just happens with "position: fixed".
Comment 1 Simon Fraser (smfr) 2013-12-30 11:15:43 PST
Hmm, we probably think it's opaque when it isn't.
Comment 2 Radar WebKit Bug Importer 2013-12-30 11:16:26 PST
Comment 3 Simon Fraser (smfr) 2014-02-17 11:02:48 PST
Created attachment 224397 [details]
Comment 4 Simon Fraser (smfr) 2014-02-17 11:08:29 PST