Bug 51435 – Issues with ContextShadow

• Status: NEW
• Component: Platform

[Simon Fraser (smfr)]

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.