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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/168882">168882</a></dd>
<dt>Author</dt> <dd>simon.fraser@apple.com</dd>
<dt>Date</dt> <dd>2014-05-14 19:33:08 -0700 (Wed, 14 May 2014)</dd>
</dl>
<h3>Log Message</h3>
<pre>[New multicolumn] Spin in RenderMultiColumnSet::repaintFlowThreadContent()
https://bugs.webkit.org/show_bug.cgi?id=132884
Reviewed by Beth Dakin.
On iOS, wikipedia pages can hang under RenderMultiColumnSet::repaintFlowThreadContent().
It appears that computedColumnHeight is set to 0 in prepareForLayout, but layout never happens
on the RenderMultiColumnSet in some cases, leaving the column height set to zero.
This caused columnIndexAtOffset() to return bad values, which resulted in very long loops
in repaintFlowThreadContent().
This fix is a stop-gap.
* rendering/RenderMultiColumnSet.cpp:
(WebCore::RenderMultiColumnSet::columnIndexAtOffset):</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceWebCoreChangeLog">trunk/Source/WebCore/ChangeLog</a></li>
<li><a href="#trunkSourceWebCorerenderingRenderMultiColumnSetcpp">trunk/Source/WebCore/rendering/RenderMultiColumnSet.cpp</a></li>
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<h3>Diff</h3>
<a id="trunkSourceWebCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/ChangeLog (168881 => 168882)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/ChangeLog 2014-05-15 00:59:26 UTC (rev 168881)
+++ trunk/Source/WebCore/ChangeLog 2014-05-15 02:33:08 UTC (rev 168882)
</span><span class="lines">@@ -1,3 +1,21 @@
</span><ins>+2014-05-14 Simon Fraser <simon.fraser@apple.com>
+
+ [New multicolumn] Spin in RenderMultiColumnSet::repaintFlowThreadContent()
+ https://bugs.webkit.org/show_bug.cgi?id=132884
+
+ Reviewed by Beth Dakin.
+
+ On iOS, wikipedia pages can hang under RenderMultiColumnSet::repaintFlowThreadContent().
+ It appears that computedColumnHeight is set to 0 in prepareForLayout, but layout never happens
+ on the RenderMultiColumnSet in some cases, leaving the column height set to zero.
+ This caused columnIndexAtOffset() to return bad values, which resulted in very long loops
+ in repaintFlowThreadContent().
+
+ This fix is a stop-gap.
+
+ * rendering/RenderMultiColumnSet.cpp:
+ (WebCore::RenderMultiColumnSet::columnIndexAtOffset):
+
</ins><span class="cx"> 2014-05-14 Benjamin Poulain <bpoulain@apple.com>
</span><span class="cx">
</span><span class="cx"> Remove FrameView::viewportConstrainedExtentRect, it is unused
</span></span></pre></div>
<a id="trunkSourceWebCorerenderingRenderMultiColumnSetcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/rendering/RenderMultiColumnSet.cpp (168881 => 168882)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/rendering/RenderMultiColumnSet.cpp 2014-05-15 00:59:26 UTC (rev 168881)
+++ trunk/Source/WebCore/rendering/RenderMultiColumnSet.cpp 2014-05-15 02:33:08 UTC (rev 168882)
</span><span class="lines">@@ -488,6 +488,10 @@
</span><span class="cx"> return columnCount() - 1;
</span><span class="cx"> }
</span><span class="cx">
</span><ins>+ // Sometimes computedColumnHeight() is 0 here: see https://bugs.webkit.org/show_bug.cgi?id=132884
+ if (!computedColumnHeight())
+ return 0;
+
</ins><span class="cx"> // Just divide by the column height to determine the correct column.
</span><span class="cx"> return static_cast<float>(offset - flowThreadLogicalTop) / computedColumnHeight();
</span><span class="cx"> }
</span></span></pre>
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