Bug 126653

Summary: Subpixel layout: RenderMultiColumnBlock::computeColumnCountAndWidth() needs flooring.
Product: WebKit Reporter: zalan <zalan>
Component: Layout and RenderingAssignee: zalan <zalan>
Severity: Normal CC: jonlee, simon.fraser, webkit-bug-importer
Priority: P2 Keywords: InRadar
Version: 528+ (Nightly build)   
Hardware: Unspecified   
OS: Unspecified   
Bug Depends on:    
Bug Blocks: 126283    
Description Flags
rendering snapshots none

Description zalan 2014-01-08 11:59:43 PST
This is rather similar to bug 126646. We produce an off by one pixel rendering when subpixel is on, though flooring it to CSS pixel would defeat the purpose of subpixel positioning the column content.

m_columnWidth = std::max<LayoutUnit>(0, (availWidth - ((m_columnCount - 1) * colGap)) / m_columnCount);

failed cases:
Comment 1 Simon Fraser (smfr) 2014-01-08 15:26:08 PST
Talk to Hyatt.
Comment 2 zalan 2014-01-15 13:07:43 PST
Created attachment 221301 [details]
rendering snapshots
Comment 3 Radar WebKit Bug Importer 2014-01-15 13:08:31 PST
Comment 4 zalan 2014-01-15 13:09:25 PST
FF(v26) rendering is in-between subpixel off and subpixel on. Prefer current subpixel rendering.