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<dl class="meta">
<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/191915">191915</a></dd>
<dt>Author</dt> <dd>zalan@apple.com</dd>
<dt>Date</dt> <dd>2015-11-02 15:16:51 -0800 (Mon, 02 Nov 2015)</dd>
</dl>

<h3>Log Message</h3>
<pre>hasOverflowClip() does not necessarily mean valid layer().
https://bugs.webkit.org/show_bug.cgi?id=150814

Reviewed by Simon Fraser.

Certain RenderLayerModelObject derived classes simply return false for ::requiresLayer(), which means
that we end up not creating a layer for the overflow clipped content.

No change in functionality.

* rendering/RenderBlock.cpp:
(WebCore::RenderBlock::updateScrollInfoAfterLayout):
(WebCore::RenderBlock::paint):
* rendering/RenderBox.cpp:
(WebCore::RenderBox::styleDidChange):
(WebCore::RenderBox::scrollWidth):
(WebCore::RenderBox::scrollHeight):
(WebCore::RenderBox::scrollLeft):
(WebCore::RenderBox::scrollTop):
(WebCore::RenderBox::setScrollLeft):
(WebCore::RenderBox::setScrollTop):
(WebCore::RenderBox::includeVerticalScrollbarSize):
(WebCore::RenderBox::includeHorizontalScrollbarSize):
(WebCore::RenderBox::intrinsicScrollbarLogicalWidth):
(WebCore::RenderBox::usesCompositedScrolling):</pre>

<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceWebCoreChangeLog">trunk/Source/WebCore/ChangeLog</a></li>
<li><a href="#trunkSourceWebCorerenderingRenderBlockcpp">trunk/Source/WebCore/rendering/RenderBlock.cpp</a></li>
<li><a href="#trunkSourceWebCorerenderingRenderBoxcpp">trunk/Source/WebCore/rendering/RenderBox.cpp</a></li>
</ul>

</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceWebCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/ChangeLog (191914 => 191915)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/ChangeLog        2015-11-02 23:03:29 UTC (rev 191914)
+++ trunk/Source/WebCore/ChangeLog        2015-11-02 23:16:51 UTC (rev 191915)
</span><span class="lines">@@ -1,3 +1,31 @@
</span><ins>+2015-11-02  Zalan Bujtas  &lt;zalan@apple.com&gt;
+
+        hasOverflowClip() does not necessarily mean valid layer().
+        https://bugs.webkit.org/show_bug.cgi?id=150814
+
+        Reviewed by Simon Fraser.
+
+        Certain RenderLayerModelObject derived classes simply return false for ::requiresLayer(), which means
+        that we end up not creating a layer for the overflow clipped content.   
+
+        No change in functionality.
+
+        * rendering/RenderBlock.cpp:
+        (WebCore::RenderBlock::updateScrollInfoAfterLayout):
+        (WebCore::RenderBlock::paint):
+        * rendering/RenderBox.cpp:
+        (WebCore::RenderBox::styleDidChange):
+        (WebCore::RenderBox::scrollWidth):
+        (WebCore::RenderBox::scrollHeight):
+        (WebCore::RenderBox::scrollLeft):
+        (WebCore::RenderBox::scrollTop):
+        (WebCore::RenderBox::setScrollLeft):
+        (WebCore::RenderBox::setScrollTop):
+        (WebCore::RenderBox::includeVerticalScrollbarSize):
+        (WebCore::RenderBox::includeHorizontalScrollbarSize):
+        (WebCore::RenderBox::intrinsicScrollbarLogicalWidth):
+        (WebCore::RenderBox::usesCompositedScrolling):
+
</ins><span class="cx"> 2015-11-02  Alex Christensen  &lt;achristensen@webkit.org&gt;
</span><span class="cx"> 
</span><span class="cx">         Fix Mac CMake build after r191904.
</span></span></pre></div>
<a id="trunkSourceWebCorerenderingRenderBlockcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/rendering/RenderBlock.cpp (191914 => 191915)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/rendering/RenderBlock.cpp        2015-11-02 23:03:29 UTC (rev 191914)
+++ trunk/Source/WebCore/rendering/RenderBlock.cpp        2015-11-02 23:16:51 UTC (rev 191915)
</span><span class="lines">@@ -900,23 +900,22 @@
</span><span class="cx"> 
</span><span class="cx"> void RenderBlock::updateScrollInfoAfterLayout()
</span><span class="cx"> {
</span><del>-    if (hasOverflowClip()) {
-        if (style().isFlippedBlocksWritingMode()) {
-            // FIXME: https://bugs.webkit.org/show_bug.cgi?id=97937
-            // Workaround for now. We cannot delay the scroll info for overflow
-            // for items with opposite writing directions, as the contents needs
-            // to overflow in that direction
-            layer()-&gt;updateScrollInfoAfterLayout();
-            return;
-        }
-
</del><ins>+    if (!hasOverflowClip())
+        return;
+    
+    // FIXME: https://bugs.webkit.org/show_bug.cgi?id=97937
+    // Workaround for now. We cannot delay the scroll info for overflow
+    // for items with opposite writing directions, as the contents needs
+    // to overflow in that direction
+    if (!style().isFlippedBlocksWritingMode()) {
</ins><span class="cx">         UpdateScrollInfoAfterLayoutTransaction* transaction = currentUpdateScrollInfoAfterLayoutTransaction();
</span><span class="cx">         if (transaction &amp;&amp; transaction-&gt;view == &amp;view()) {
</span><span class="cx">             transaction-&gt;blocks.add(this);
</span><span class="cx">             return;
</span><span class="cx">         }
</span><ins>+    }
+    if (layer())
</ins><span class="cx">         layer()-&gt;updateScrollInfoAfterLayout();
</span><del>-    }
</del><span class="cx"> }
</span><span class="cx"> 
</span><span class="cx"> void RenderBlock::layout()
</span><span class="lines">@@ -1423,9 +1422,10 @@
</span><span class="cx">         popContentsClip(paintInfo, phase, adjustedPaintOffset);
</span><span class="cx"> 
</span><span class="cx">     // Our scrollbar widgets paint exactly when we tell them to, so that they work properly with
</span><del>-    // z-index.  We paint after we painted the background/border, so that the scrollbars will
</del><ins>+    // z-index. We paint after we painted the background/border, so that the scrollbars will
</ins><span class="cx">     // sit above the background/border.
</span><del>-    if ((phase == PaintPhaseBlockBackground || phase == PaintPhaseChildBlockBackground) &amp;&amp; hasOverflowClip() &amp;&amp; style().visibility() == VISIBLE &amp;&amp; paintInfo.shouldPaintWithinRoot(*this) &amp;&amp; !paintInfo.paintRootBackgroundOnly())
</del><ins>+    if ((phase == PaintPhaseBlockBackground || phase == PaintPhaseChildBlockBackground) &amp;&amp; hasOverflowClip() &amp;&amp; layer()
+        &amp;&amp; style().visibility() == VISIBLE &amp;&amp; paintInfo.shouldPaintWithinRoot(*this) &amp;&amp; !paintInfo.paintRootBackgroundOnly())
</ins><span class="cx">         layer()-&gt;paintOverflowControls(paintInfo.context(), roundedIntPoint(adjustedPaintOffset), snappedIntRect(paintInfo.rect));
</span><span class="cx"> }
</span><span class="cx"> 
</span></span></pre></div>
<a id="trunkSourceWebCorerenderingRenderBoxcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/rendering/RenderBox.cpp (191914 => 191915)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/rendering/RenderBox.cpp        2015-11-02 23:03:29 UTC (rev 191914)
+++ trunk/Source/WebCore/rendering/RenderBox.cpp        2015-11-02 23:16:51 UTC (rev 191915)
</span><span class="lines">@@ -352,7 +352,7 @@
</span><span class="cx"> 
</span><span class="cx">     // If our zoom factor changes and we have a defined scrollLeft/Top, we need to adjust that value into the
</span><span class="cx">     // new zoomed coordinate space.
</span><del>-    if (hasOverflowClip() &amp;&amp; oldStyle &amp;&amp; oldStyle-&gt;effectiveZoom() != newStyle.effectiveZoom() &amp;&amp; layer()) {
</del><ins>+    if (hasOverflowClip() &amp;&amp; layer() &amp;&amp; oldStyle &amp;&amp; oldStyle-&gt;effectiveZoom() != newStyle.effectiveZoom()) {
</ins><span class="cx">         if (int left = layer()-&gt;scrollXOffset()) {
</span><span class="cx">             left = (left / oldStyle-&gt;effectiveZoom()) * newStyle.effectiveZoom();
</span><span class="cx">             layer()-&gt;scrollToXOffset(left);
</span><span class="lines">@@ -552,7 +552,7 @@
</span><span class="cx"> 
</span><span class="cx"> int RenderBox::scrollWidth() const
</span><span class="cx"> {
</span><del>-    if (hasOverflowClip())
</del><ins>+    if (hasOverflowClip() &amp;&amp; layer())
</ins><span class="cx">         return layer()-&gt;scrollWidth();
</span><span class="cx">     // For objects with visible overflow, this matches IE.
</span><span class="cx">     // FIXME: Need to work right with writing modes.
</span><span class="lines">@@ -565,7 +565,7 @@
</span><span class="cx"> 
</span><span class="cx"> int RenderBox::scrollHeight() const
</span><span class="cx"> {
</span><del>-    if (hasOverflowClip())
</del><ins>+    if (hasOverflowClip() &amp;&amp; layer())
</ins><span class="cx">         return layer()-&gt;scrollHeight();
</span><span class="cx">     // For objects with visible overflow, this matches IE.
</span><span class="cx">     // FIXME: Need to work right with writing modes.
</span><span class="lines">@@ -575,12 +575,12 @@
</span><span class="cx"> 
</span><span class="cx"> int RenderBox::scrollLeft() const
</span><span class="cx"> {
</span><del>-    return hasOverflowClip() ? layer()-&gt;scrollXOffset() : 0;
</del><ins>+    return hasOverflowClip() &amp;&amp; layer() ? layer()-&gt;scrollXOffset() : 0;
</ins><span class="cx"> }
</span><span class="cx"> 
</span><span class="cx"> int RenderBox::scrollTop() const
</span><span class="cx"> {
</span><del>-    return hasOverflowClip() ? layer()-&gt;scrollYOffset() : 0;
</del><ins>+    return hasOverflowClip() &amp;&amp; layer() ? layer()-&gt;scrollYOffset() : 0;
</ins><span class="cx"> }
</span><span class="cx"> 
</span><span class="cx"> static void setupWheelEventTestTrigger(RenderLayer&amp; layer, Frame* frame)
</span><span class="lines">@@ -597,18 +597,18 @@
</span><span class="cx"> 
</span><span class="cx"> void RenderBox::setScrollLeft(int newLeft)
</span><span class="cx"> {
</span><del>-    if (hasOverflowClip()) {
-        setupWheelEventTestTrigger(*layer(), document().frame());
-        layer()-&gt;scrollToXOffset(newLeft, RenderLayer::ScrollOffsetClamped);
-    }
</del><ins>+    if (!hasOverflowClip() || !layer())
+        return;
+    setupWheelEventTestTrigger(*layer(), document().frame());
+    layer()-&gt;scrollToXOffset(newLeft, RenderLayer::ScrollOffsetClamped);
</ins><span class="cx"> }
</span><span class="cx"> 
</span><span class="cx"> void RenderBox::setScrollTop(int newTop)
</span><span class="cx"> {
</span><del>-    if (hasOverflowClip()) {
-        setupWheelEventTestTrigger(*layer(), document().frame());
-        layer()-&gt;scrollToYOffset(newTop, RenderLayer::ScrollOffsetClamped);
-    }
</del><ins>+    if (!hasOverflowClip() || !layer())
+        return;
+    setupWheelEventTestTrigger(*layer(), document().frame());
+    layer()-&gt;scrollToYOffset(newTop, RenderLayer::ScrollOffsetClamped);
</ins><span class="cx"> }
</span><span class="cx"> 
</span><span class="cx"> void RenderBox::absoluteRects(Vector&lt;IntRect&gt;&amp; rects, const LayoutPoint&amp; accumulatedOffset) const
</span><span class="lines">@@ -761,13 +761,13 @@
</span><span class="cx"> 
</span><span class="cx"> bool RenderBox::includeVerticalScrollbarSize() const
</span><span class="cx"> {
</span><del>-    return hasOverflowClip() &amp;&amp; !layer()-&gt;hasOverlayScrollbars()
</del><ins>+    return hasOverflowClip() &amp;&amp; layer() &amp;&amp; !layer()-&gt;hasOverlayScrollbars()
</ins><span class="cx">         &amp;&amp; (style().overflowY() == OSCROLL || style().overflowY() == OAUTO);
</span><span class="cx"> }
</span><span class="cx"> 
</span><span class="cx"> bool RenderBox::includeHorizontalScrollbarSize() const
</span><span class="cx"> {
</span><del>-    return hasOverflowClip() &amp;&amp; !layer()-&gt;hasOverlayScrollbars()
</del><ins>+    return hasOverflowClip() &amp;&amp; layer() &amp;&amp; !layer()-&gt;hasOverlayScrollbars()
</ins><span class="cx">         &amp;&amp; (style().overflowX() == OSCROLL || style().overflowX() == OAUTO);
</span><span class="cx"> }
</span><span class="cx"> 
</span><span class="lines">@@ -787,12 +787,12 @@
</span><span class="cx">         return 0;
</span><span class="cx"> 
</span><span class="cx">     if (isHorizontalWritingMode() &amp;&amp; (style().overflowY() == OSCROLL &amp;&amp; !hasVerticalScrollbarWithAutoBehavior())) {
</span><del>-        ASSERT(layer()-&gt;hasVerticalScrollbar());
</del><ins>+        ASSERT(layer() &amp;&amp; layer()-&gt;hasVerticalScrollbar());
</ins><span class="cx">         return verticalScrollbarWidth();
</span><span class="cx">     }
</span><span class="cx"> 
</span><span class="cx">     if (!isHorizontalWritingMode() &amp;&amp; (style().overflowX() == OSCROLL &amp;&amp; !hasHorizontalScrollbarWithAutoBehavior())) {
</span><del>-        ASSERT(layer()-&gt;hasHorizontalScrollbar());
</del><ins>+        ASSERT(layer() &amp;&amp; layer()-&gt;hasHorizontalScrollbar());
</ins><span class="cx">         return horizontalScrollbarHeight();
</span><span class="cx">     }
</span><span class="cx"> 
</span></span></pre>
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