[Webkit-unassigned] [Bug 51435] New: Issues with ContextShadow

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=51435

           Summary: Issues with ContextShadow
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: PC
        OS/Version: Mac OS X 10.5
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Platform
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: simon.fraser at apple.com
                CC: alex at igalia.com, mrobinson at webkit.org


I see some issues with ContextShadow:

1. Code cleanup:
 * Rename drawRectShadowWithoutTiling to drawUntiledRectShadow
 * Move tiled drawing code into drawRectShadowWithTiling
 * drawRectShadow() just calls one or the other

2. layer area calculation
  * the code that inflates the shadow rect by the radius happens in both drawRectShadow, and again down in calculateLayerBoundingRect. 
  * when drawRectShadow() calls calculateLayerBoundingRect, it passes the already-inflated rect, leading to double inflation, I think. This does not happen in the drawRectShadowWithoutTiling code path.

3. Clipping causes double inflation
  * the "intersect with the clip" code in calculateLayerBoundingRect can cause double inflation on sides of the shadow that are not clipped. I think you want to intersect with an inflated clip.

4. The comment for m_sourceRect is wrong. m_sourceRect can end up larger than the layer buffer when clipped. There is no member var that tracks the rect in the layer buffer to which blurring should be applied.

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