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<div id="msg">
<dl class="meta">
<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/151622">151622</a></dd>
<dt>Author</dt> <dd>simon.fraser@apple.com</dd>
<dt>Date</dt> <dd>2013-06-16 09:57:14 -0700 (Sun, 16 Jun 2013)</dd>
</dl>

<h3>Log Message</h3>
<pre>webkit-backface-visibility on a parent element stops background-position from updating
https://bugs.webkit.org/show_bug.cgi?id=116319

Source/WebCore:

Reviewed by Darin Adler.

The optimization added in <a href="http://trac.webkit.org/projects/webkit/changeset/102952">r102952</a> was incorrect in the case where a style change
resulted in a positioned-movement-only layout but also required a repaint; it assumed
that a composited layer did not need to be repainted for a a positioned-movement-only layout.

Fix by making RenderObject::setNeedsLayoutForPositionedMovement() check whether the
style change requires a repaint, and calling setLayerNeedsFullRepaint() in that situation.

Test: compositing/repaint/positioned-movement.html

* rendering/RenderLayer.h: RepaintStatus values do not need to be bit flags.
* rendering/RenderObject.cpp:
(WebCore::RenderObject::setStyle): Pass the old style to setNeedsPositionedMovementLayout().
(WebCore::RenderObject::styleDidChange): Ditto.
* rendering/RenderObject.h:
(WebCore::RenderObject::setNeedsPositionedMovementLayout): Now takes a const RenderStyle*.
* rendering/style/RenderStyle.cpp:
(WebCore::RenderStyle::diff): Remove a comment now that this bug is fixed.
(WebCore::RenderStyle::diffRequiresRepaint): Public wrapper for changeRequiresRepaint().
That function never uses contextSensitiveProperties so we can safely ignore them.
* rendering/style/RenderStyle.h: Expose a way to call changeRequiresRepaint().

LayoutTests:

Reviewed by Darin Adler.

Test that does a positioned-movement-only layout and dumps a layer tree with
repaint rects.

* compositing/repaint/positioned-movement-expected.txt: Added.
* compositing/repaint/positioned-movement.html: Added.</pre>

<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkLayoutTestsChangeLog">trunk/LayoutTests/ChangeLog</a></li>
<li><a href="#trunkSourceWebCoreChangeLog">trunk/Source/WebCore/ChangeLog</a></li>
<li><a href="#trunkSourceWebCorerenderingRenderLayerh">trunk/Source/WebCore/rendering/RenderLayer.h</a></li>
<li><a href="#trunkSourceWebCorerenderingRenderObjectcpp">trunk/Source/WebCore/rendering/RenderObject.cpp</a></li>
<li><a href="#trunkSourceWebCorerenderingRenderObjecth">trunk/Source/WebCore/rendering/RenderObject.h</a></li>
<li><a href="#trunkSourceWebCorerenderingstyleRenderStylecpp">trunk/Source/WebCore/rendering/style/RenderStyle.cpp</a></li>
<li><a href="#trunkSourceWebCorerenderingstyleRenderStyleh">trunk/Source/WebCore/rendering/style/RenderStyle.h</a></li>
</ul>

<h3>Added Paths</h3>
<ul>
<li><a href="#trunkLayoutTestscompositingrepaintpositionedmovementexpectedtxt">trunk/LayoutTests/compositing/repaint/positioned-movement-expected.txt</a></li>
<li><a href="#trunkLayoutTestscompositingrepaintpositionedmovementhtml">trunk/LayoutTests/compositing/repaint/positioned-movement.html</a></li>
</ul>

</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkLayoutTestsChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/LayoutTests/ChangeLog (151621 => 151622)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/ChangeLog        2013-06-16 15:06:30 UTC (rev 151621)
+++ trunk/LayoutTests/ChangeLog        2013-06-16 16:57:14 UTC (rev 151622)
</span><span class="lines">@@ -1,3 +1,16 @@
</span><ins>+2013-06-15  Simon Fraser  &lt;simon.fraser@apple.com&gt;
+
+        webkit-backface-visibility on a parent element stops background-position from updating
+        https://bugs.webkit.org/show_bug.cgi?id=116319
+
+        Reviewed by Darin Adler.
+        
+        Test that does a positioned-movement-only layout and dumps a layer tree with
+        repaint rects.
+
+        * compositing/repaint/positioned-movement-expected.txt: Added.
+        * compositing/repaint/positioned-movement.html: Added.
+
</ins><span class="cx"> 2013-06-14  Robert Hogan  &lt;robert@webkit.org&gt;
</span><span class="cx"> 
</span><span class="cx">         REGRESSION (r148367): Facebook and Twitter icons at macworld.com are stacked vertically, obscuring Twitter one
</span></span></pre></div>
<a id="trunkLayoutTestscompositingrepaintpositionedmovementexpectedtxt"></a>
<div class="addfile"><h4>Added: trunk/LayoutTests/compositing/repaint/positioned-movement-expected.txt (0 => 151622)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/compositing/repaint/positioned-movement-expected.txt                                (rev 0)
+++ trunk/LayoutTests/compositing/repaint/positioned-movement-expected.txt        2013-06-16 16:57:14 UTC (rev 151622)
</span><span class="lines">@@ -0,0 +1,20 @@
</span><ins>+(GraphicsLayer
+  (bounds 800.00 600.00)
+  (children 1
+    (GraphicsLayer
+      (bounds 800.00 600.00)
+      (contentsOpaque 1)
+      (children 1
+        (GraphicsLayer
+          (position 110.00 110.00)
+          (bounds 400.00 400.00)
+          (drawsContent 1)
+          (repaint rects
+            (rect 0.00 0.00 400.00 400.00)
+          )
+        )
+      )
+    )
+  )
+)
+
</ins></span></pre></div>
<a id="trunkLayoutTestscompositingrepaintpositionedmovementhtml"></a>
<div class="addfile"><h4>Added: trunk/LayoutTests/compositing/repaint/positioned-movement.html (0 => 151622)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/compositing/repaint/positioned-movement.html                                (rev 0)
+++ trunk/LayoutTests/compositing/repaint/positioned-movement.html        2013-06-16 16:57:14 UTC (rev 151622)
</span><span class="lines">@@ -0,0 +1,56 @@
</span><ins>+&lt;!DOCTYPE html&gt;
+
+&lt;html&gt;
+&lt;head&gt;
+    &lt;style&gt;
+        .box {
+            position: absolute;
+            top: 10px;
+            left: 10px;
+            width: 400px;
+            height: 400px;
+            background-image: url('../resources/alpha-blocks.png');
+            background-size: 400px 400px;
+        }
+        
+        #box.moved {
+            background-position: -100px -100px;
+            top: 110px;
+            left: 110px;
+        }
+        
+        .composited {
+            -webkit-transform: translateZ(0);
+        }
+    &lt;/style&gt;
+    &lt;script&gt;
+        if (window.testRunner) {
+            testRunner.dumpAsText();
+            testRunner.waitUntilDone();
+        }
+
+        function test()
+        {
+            window.setTimeout(function() {
+                document.body.offsetTop;
+                if (window.internals)
+                    window.internals.startTrackingRepaints(document);
+
+                document.getElementById('box').classList.add('moved');
+
+                if (window.internals)
+                    document.getElementById('repaintRects').textContent = window.internals.layerTreeAsText(document, internals.LAYER_TREE_INCLUDES_REPAINT_RECTS);
+
+                if (window.testRunner)
+                    testRunner.notifyDone();
+            }, 0);
+        }
+        window.addEventListener('load', test, false);
+    &lt;/script&gt;
+&lt;/head&gt;
+&lt;body&gt;
+
+    &lt;div id=&quot;box&quot; class=&quot;composited box&quot;&gt;&lt;/div&gt;
+    &lt;pre id=&quot;repaintRects&quot;&gt;&lt;/pre&gt;
+&lt;/body&gt;
+&lt;/html&gt;
</ins></span></pre></div>
<a id="trunkSourceWebCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/ChangeLog (151621 => 151622)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/ChangeLog        2013-06-16 15:06:30 UTC (rev 151621)
+++ trunk/Source/WebCore/ChangeLog        2013-06-16 16:57:14 UTC (rev 151622)
</span><span class="lines">@@ -1,3 +1,31 @@
</span><ins>+2013-06-15  Simon Fraser  &lt;simon.fraser@apple.com&gt;
+
+        webkit-backface-visibility on a parent element stops background-position from updating
+        https://bugs.webkit.org/show_bug.cgi?id=116319
+
+        Reviewed by Darin Adler.
+
+        The optimization added in r102952 was incorrect in the case where a style change
+        resulted in a positioned-movement-only layout but also required a repaint; it assumed
+        that a composited layer did not need to be repainted for a a positioned-movement-only layout.
+        
+        Fix by making RenderObject::setNeedsLayoutForPositionedMovement() check whether the
+        style change requires a repaint, and calling setLayerNeedsFullRepaint() in that situation.
+
+        Test: compositing/repaint/positioned-movement.html
+
+        * rendering/RenderLayer.h: RepaintStatus values do not need to be bit flags.
+        * rendering/RenderObject.cpp:
+        (WebCore::RenderObject::setStyle): Pass the old style to setNeedsPositionedMovementLayout().
+        (WebCore::RenderObject::styleDidChange): Ditto.
+        * rendering/RenderObject.h:
+        (WebCore::RenderObject::setNeedsPositionedMovementLayout): Now takes a const RenderStyle*.
+        * rendering/style/RenderStyle.cpp:
+        (WebCore::RenderStyle::diff): Remove a comment now that this bug is fixed.
+        (WebCore::RenderStyle::diffRequiresRepaint): Public wrapper for changeRequiresRepaint().
+        That function never uses contextSensitiveProperties so we can safely ignore them.
+        * rendering/style/RenderStyle.h: Expose a way to call changeRequiresRepaint().
+
</ins><span class="cx"> 2013-06-15  Darin Adler  &lt;darin@apple.com&gt;
</span><span class="cx"> 
</span><span class="cx">         Try to fix iOS after last Pasteboard change.
</span></span></pre></div>
<a id="trunkSourceWebCorerenderingRenderLayerh"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/rendering/RenderLayer.h (151621 => 151622)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/rendering/RenderLayer.h        2013-06-16 15:06:30 UTC (rev 151621)
+++ trunk/Source/WebCore/rendering/RenderLayer.h        2013-06-16 16:57:14 UTC (rev 151622)
</span><span class="lines">@@ -79,9 +79,9 @@
</span><span class="cx"> enum IncludeSelfOrNot { IncludeSelf, ExcludeSelf };
</span><span class="cx"> 
</span><span class="cx"> enum RepaintStatus {
</span><del>-    NeedsNormalRepaint = 0,
-    NeedsFullRepaint = 1 &lt;&lt; 0,
-    NeedsFullRepaintForPositionedMovementLayout = 1 &lt;&lt; 1
</del><ins>+    NeedsNormalRepaint,
+    NeedsFullRepaint,
+    NeedsFullRepaintForPositionedMovementLayout
</ins><span class="cx"> };
</span><span class="cx"> 
</span><span class="cx"> class ClipRect {
</span></span></pre></div>
<a id="trunkSourceWebCorerenderingRenderObjectcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/rendering/RenderObject.cpp (151621 => 151622)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/rendering/RenderObject.cpp        2013-06-16 15:06:30 UTC (rev 151621)
+++ trunk/Source/WebCore/rendering/RenderObject.cpp        2013-06-16 16:57:14 UTC (rev 151622)
</span><span class="lines">@@ -1868,9 +1868,9 @@
</span><span class="cx">         if (updatedDiff == StyleDifferenceLayout)
</span><span class="cx">             setNeedsLayoutAndPrefWidthsRecalc();
</span><span class="cx">         else if (updatedDiff == StyleDifferenceLayoutPositionedMovementOnly)
</span><del>-            setNeedsPositionedMovementLayout();
</del><ins>+            setNeedsPositionedMovementLayout(oldStyle.get());
</ins><span class="cx">         else if (updatedDiff == StyleDifferenceSimplifiedLayoutAndPositionedMovement) {
</span><del>-            setNeedsPositionedMovementLayout();
</del><ins>+            setNeedsPositionedMovementLayout(oldStyle.get());
</ins><span class="cx">             setNeedsSimplifiedNormalFlowLayout();
</span><span class="cx">         } else if (updatedDiff == StyleDifferenceSimplifiedLayout)
</span><span class="cx">             setNeedsSimplifiedNormalFlowLayout();
</span><span class="lines">@@ -2022,10 +2022,10 @@
</span><span class="cx">         else
</span><span class="cx">             setNeedsSimplifiedNormalFlowLayout();
</span><span class="cx">     } else if (diff == StyleDifferenceSimplifiedLayoutAndPositionedMovement) {
</span><del>-        setNeedsPositionedMovementLayout();
</del><ins>+        setNeedsPositionedMovementLayout(oldStyle);
</ins><span class="cx">         setNeedsSimplifiedNormalFlowLayout();
</span><span class="cx">     } else if (diff == StyleDifferenceLayoutPositionedMovementOnly)
</span><del>-        setNeedsPositionedMovementLayout();
</del><ins>+        setNeedsPositionedMovementLayout(oldStyle);
</ins><span class="cx"> 
</span><span class="cx">     // Don't check for repaint here; we need to wait until the layer has been
</span><span class="cx">     // updated by subclasses before we know if we have to repaint (in setStyle()).
</span></span></pre></div>
<a id="trunkSourceWebCorerenderingRenderObjecth"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/rendering/RenderObject.h (151621 => 151622)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/rendering/RenderObject.h        2013-06-16 15:06:30 UTC (rev 151621)
+++ trunk/Source/WebCore/rendering/RenderObject.h        2013-06-16 16:57:14 UTC (rev 151622)
</span><span class="lines">@@ -665,7 +665,7 @@
</span><span class="cx">     void markContainingBlocksForLayout(bool scheduleRelayout = true, RenderObject* newRoot = 0);
</span><span class="cx">     void setNeedsLayout(bool needsLayout, MarkingBehavior = MarkContainingBlockChain);
</span><span class="cx">     void setChildNeedsLayout(bool childNeedsLayout, MarkingBehavior = MarkContainingBlockChain);
</span><del>-    void setNeedsPositionedMovementLayout();
</del><ins>+    void setNeedsPositionedMovementLayout(const RenderStyle* oldStyle);
</ins><span class="cx">     void setNeedsSimplifiedNormalFlowLayout();
</span><span class="cx">     void setPreferredLogicalWidthsDirty(bool, MarkingBehavior = MarkContainingBlockChain);
</span><span class="cx">     void invalidateContainerPreferredLogicalWidths();
</span><span class="lines">@@ -1244,15 +1244,19 @@
</span><span class="cx">     }
</span><span class="cx"> }
</span><span class="cx"> 
</span><del>-inline void RenderObject::setNeedsPositionedMovementLayout()
</del><ins>+inline void RenderObject::setNeedsPositionedMovementLayout(const RenderStyle* oldStyle)
</ins><span class="cx"> {
</span><span class="cx">     bool alreadyNeededLayout = needsPositionedMovementLayout();
</span><span class="cx">     setNeedsPositionedMovementLayout(true);
</span><span class="cx">     ASSERT(!isSetNeedsLayoutForbidden());
</span><span class="cx">     if (!alreadyNeededLayout) {
</span><span class="cx">         markContainingBlocksForLayout();
</span><del>-        if (hasLayer())
-            setLayerNeedsFullRepaintForPositionedMovementLayout();
</del><ins>+        if (hasLayer()) {
+            if (oldStyle &amp;&amp; m_style-&gt;diffRequiresRepaint(oldStyle))
+                setLayerNeedsFullRepaint();
+            else
+                setLayerNeedsFullRepaintForPositionedMovementLayout();
+        }
</ins><span class="cx">     }
</span><span class="cx"> }
</span><span class="cx"> 
</span></span></pre></div>
<a id="trunkSourceWebCorerenderingstyleRenderStylecpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/rendering/style/RenderStyle.cpp (151621 => 151622)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/rendering/style/RenderStyle.cpp        2013-06-16 15:06:30 UTC (rev 151621)
+++ trunk/Source/WebCore/rendering/style/RenderStyle.cpp        2013-06-16 16:57:14 UTC (rev 151622)
</span><span class="lines">@@ -767,8 +767,6 @@
</span><span class="cx">         return svgChange;
</span><span class="cx"> #endif
</span><span class="cx"> 
</span><del>-    // FIXME: we need to also check for repaint changes after a PositionedMovementOnly change
-    // on a composited layer: https://bugs.webkit.org/show_bug.cgi?id=116319
</del><span class="cx">     if (changeRequiresPositionedLayoutOnly(other, changedContextSensitiveProperties))
</span><span class="cx">         return StyleDifferenceLayoutPositionedMovementOnly;
</span><span class="cx"> 
</span><span class="lines">@@ -794,6 +792,12 @@
</span><span class="cx">     return StyleDifferenceEqual;
</span><span class="cx"> }
</span><span class="cx"> 
</span><ins>+bool RenderStyle::diffRequiresRepaint(const RenderStyle* style) const
+{
+    unsigned changedContextSensitiveProperties = 0;
+    return changeRequiresRepaint(style, changedContextSensitiveProperties);
+}
+
</ins><span class="cx"> void RenderStyle::setClip(Length top, Length right, Length bottom, Length left)
</span><span class="cx"> {
</span><span class="cx">     StyleVisualData* data = visual.access();
</span></span></pre></div>
<a id="trunkSourceWebCorerenderingstyleRenderStyleh"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/rendering/style/RenderStyle.h (151621 => 151622)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/rendering/style/RenderStyle.h        2013-06-16 15:06:30 UTC (rev 151621)
+++ trunk/Source/WebCore/rendering/style/RenderStyle.h        2013-06-16 16:57:14 UTC (rev 151622)
</span><span class="lines">@@ -1535,6 +1535,7 @@
</span><span class="cx">     bool inheritedDataShared(const RenderStyle*) const;
</span><span class="cx"> 
</span><span class="cx">     StyleDifference diff(const RenderStyle*, unsigned&amp; changedContextSensitiveProperties) const;
</span><ins>+    bool diffRequiresRepaint(const RenderStyle*) const;
</ins><span class="cx"> 
</span><span class="cx">     bool isDisplayReplacedType() const { return isDisplayReplacedType(display()); }
</span><span class="cx">     bool isDisplayInlineType() const { return isDisplayInlineType(display()); }
</span></span></pre>
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