Bug 126646 - Subpixel layout: desiredColumnWidth in RenderBlock::calcColumnWidth() needs flooring.
Summary: Subpixel layout: desiredColumnWidth in RenderBlock::calcColumnWidth() needs f...
Status: RESOLVED INVALID
Alias: None
Product: WebKit
Classification: Unclassified
Component: Layout and Rendering (show other bugs)
Version: 528+ (Nightly build)
Hardware: Unspecified Unspecified
: P2 Normal
Assignee: zalan
URL:
Keywords:
Depends on:
Blocks: 126283
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Reported: 2014-01-08 10:46 PST by zalan
Modified: 2014-01-14 16:39 PST (History)
3 users (show)

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Description zalan 2014-01-08 10:46:06 PST 
LayoutUnit desiredColumnWidth = std::max<LayoutUnit>(0, ((availWidth - ((desiredColumnCount - 1) * colGap)) / desiredColumnCount)) produces different CSS pixel results when subpixel is off.

failed case:
  fast/events/document-elementFromPoint.html
  fast/multicol/break-properties.html
  fast/multicol/column-break-with-balancing.html
  fast/multicol/float-paginate-complex.html
  fast/multicol/layers-in-multicol.html
  fast/multicol/overflow-across-columns-percent-height.html
  fast/multicol/overflow-across-columns.html
  fast/multicol/overflow-unsplittable.html
  fast/multicol/scrolling-overflow.html 
  fast/multicol/span/clone-flexbox.html 
  fast/multicol/span/clone-summary.html 
  fast/multicol/table-vertical-align.html
  fast/multicol/vertical-lr/break-properties.html 
  fast/multicol/vertical-lr/column-break-with-balancing.html
  fast/multicol/vertical-lr/float-multicol.html 
  fast/multicol/vertical-rl/break-properties.html
  fast/multicol/vertical-rl/column-break-with-balancing.html 
  fast/multicol/vertical-rl/float-multicol.html 
  fast/multicol/newmulticol/column-rules-fixed-height.html 
  fast/multicol/newmulticol/columns-shorthand-parsing.html
  fast/multicol/newmulticol/layers-in-multicol.html
Comment 1 zalan 2014-01-08 11:17:28 PST 
If we start snapping columns widths to CSS pixels, we lose subpixels while layouting the columns content.
Comment 2 Simon Fraser (smfr) 2014-01-08 15:22:04 PST 
Need to talk to Dave Hyatt.
Comment 3 zalan 2014-01-14 16:39:33 PST 
Matches FF(v26) rendering.