in RenderObject::drawLineForBoxSide() we check whether the border thickness and length are > 0. Flooring is used to avoid painting empty lines. In certain cases, when we lose precession while converting float <-> LayoutUnit back and forth, flooring a border width value of 0.5px (before conversions and 0.49999 after conversions) becomes 0 and we early return from painting.
Created attachment 236169 [details] Patch
Comment on attachment 236169 [details] Patch View in context: https://bugs.webkit.org/attachment.cgi?id=236169&action=review > Source/WebCore/ChangeLog:10 > + empty border rect drawing can lead to false positives. false positives of what?
Created attachment 236256 [details] Patch
Comment on attachment 236256 [details] Patch Clearing flags on attachment: 236256 Committed r172326: <http://trac.webkit.org/changeset/172326>
All reviewed patches have been landed. Closing bug.
(In reply to comment #4) > Comment on attachment 236256 [details] > Patch > > Clearing flags on attachment: 236256 > > Committed r172326: <http://trac.webkit.org/changeset/172326> Note that this change caused: Bug 135898: Dashed/dotted borders do not paint. <https://bugs.webkit.org/show_bug.cgi?id=135898>