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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/246019">246019</a></dd>
<dt>Author</dt> <dd>simon.fraser@apple.com</dd>
<dt>Date</dt> <dd>2019-06-01 20:01:47 -0700 (Sat, 01 Jun 2019)</dd>
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<h3>Log Message</h3>
<pre>[Async overflow scroll] Flashing content when scrolling async overflow with a negative z-index child
https://bugs.webkit.org/show_bug.cgi?id=198458

Reviewed by Dean Jackson.

Source/WebCore:

Set the GraphicsLayerPaintOverflowContents phase on the foreground layer in a composited overflow scroller,
which prevents clipping to the visible region, fixing scrolling flashes.

Tested by compositing/overflow/stacking-context-composited-scroller-with-foreground-paint-phases.html

* rendering/RenderLayerBacking.cpp:
(WebCore::RenderLayerBacking::updatePaintingPhases):

LayoutTests:

* compositing/overflow/stacking-context-composited-scroller-with-foreground-paint-phases-expected.txt:
* platform/ios-wk2/compositing/overflow/stacking-context-composited-scroller-with-foreground-paint-phases-expected.txt:</pre>

<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkLayoutTestsChangeLog">trunk/LayoutTests/ChangeLog</a></li>
<li><a href="#trunkLayoutTestscompositingoverflowstackingcontextcompositedscrollerwithforegroundpaintphasesexpectedtxt">trunk/LayoutTests/compositing/overflow/stacking-context-composited-scroller-with-foreground-paint-phases-expected.txt</a></li>
<li><a href="#trunkLayoutTestsplatformioswk2compositingoverflowstackingcontextcompositedscrollerwithforegroundpaintphasesexpectedtxt">trunk/LayoutTests/platform/ios-wk2/compositing/overflow/stacking-context-composited-scroller-with-foreground-paint-phases-expected.txt</a></li>
<li><a href="#trunkSourceWebCoreChangeLog">trunk/Source/WebCore/ChangeLog</a></li>
<li><a href="#trunkSourceWebCorerenderingRenderLayerBackingcpp">trunk/Source/WebCore/rendering/RenderLayerBacking.cpp</a></li>
</ul>

</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkLayoutTestsChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/LayoutTests/ChangeLog (246018 => 246019)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/ChangeLog      2019-06-02 02:55:57 UTC (rev 246018)
+++ trunk/LayoutTests/ChangeLog 2019-06-02 03:01:47 UTC (rev 246019)
</span><span class="lines">@@ -1,5 +1,15 @@
</span><span class="cx"> 2019-06-01  Simon Fraser  <simon.fraser@apple.com>
</span><span class="cx"> 
</span><ins>+        [Async overflow scroll] Flashing content when scrolling async overflow with a negative z-index child
+        https://bugs.webkit.org/show_bug.cgi?id=198458
+
+        Reviewed by Dean Jackson.
+
+        * compositing/overflow/stacking-context-composited-scroller-with-foreground-paint-phases-expected.txt:
+        * platform/ios-wk2/compositing/overflow/stacking-context-composited-scroller-with-foreground-paint-phases-expected.txt:
+
+2019-06-01  Simon Fraser  <simon.fraser@apple.com>
+
</ins><span class="cx">         Async overflow scroll on iOS paints slowly if it has a negative z-index child
</span><span class="cx">         https://bugs.webkit.org/show_bug.cgi?id=196508
</span><span class="cx">         rdar://problem/49532709
</span></span></pre></div>
<a id="trunkLayoutTestscompositingoverflowstackingcontextcompositedscrollerwithforegroundpaintphasesexpectedtxt"></a>
<div class="modfile"><h4>Modified: trunk/LayoutTests/compositing/overflow/stacking-context-composited-scroller-with-foreground-paint-phases-expected.txt (246018 => 246019)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/compositing/overflow/stacking-context-composited-scroller-with-foreground-paint-phases-expected.txt    2019-06-02 02:55:57 UTC (rev 246018)
+++ trunk/LayoutTests/compositing/overflow/stacking-context-composited-scroller-with-foreground-paint-phases-expected.txt       2019-06-02 03:01:47 UTC (rev 246019)
</span><span class="lines">@@ -54,6 +54,7 @@
</span><span class="cx">                       (drawsContent 1)
</span><span class="cx">                       (paintingPhases
</span><span class="cx">                         GraphicsLayerPaintForeground
</span><ins>+                        GraphicsLayerPaintOverflowContents
</ins><span class="cx">                         )
</span><span class="cx">                     )
</span><span class="cx">                   )
</span></span></pre></div>
<a id="trunkLayoutTestsplatformioswk2compositingoverflowstackingcontextcompositedscrollerwithforegroundpaintphasesexpectedtxt"></a>
<div class="modfile"><h4>Modified: trunk/LayoutTests/platform/ios-wk2/compositing/overflow/stacking-context-composited-scroller-with-foreground-paint-phases-expected.txt (246018 => 246019)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/platform/ios-wk2/compositing/overflow/stacking-context-composited-scroller-with-foreground-paint-phases-expected.txt   2019-06-02 02:55:57 UTC (rev 246018)
+++ trunk/LayoutTests/platform/ios-wk2/compositing/overflow/stacking-context-composited-scroller-with-foreground-paint-phases-expected.txt      2019-06-02 03:01:47 UTC (rev 246019)
</span><span class="lines">@@ -54,6 +54,7 @@
</span><span class="cx">                       (drawsContent 1)
</span><span class="cx">                       (paintingPhases
</span><span class="cx">                         GraphicsLayerPaintForeground
</span><ins>+                        GraphicsLayerPaintOverflowContents
</ins><span class="cx">                         )
</span><span class="cx">                     )
</span><span class="cx">                   )
</span></span></pre></div>
<a id="trunkSourceWebCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/ChangeLog (246018 => 246019)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/ChangeLog   2019-06-02 02:55:57 UTC (rev 246018)
+++ trunk/Source/WebCore/ChangeLog      2019-06-02 03:01:47 UTC (rev 246019)
</span><span class="lines">@@ -1,5 +1,20 @@
</span><span class="cx"> 2019-06-01  Simon Fraser  <simon.fraser@apple.com>
</span><span class="cx"> 
</span><ins>+        [Async overflow scroll] Flashing content when scrolling async overflow with a negative z-index child
+        https://bugs.webkit.org/show_bug.cgi?id=198458
+
+        Reviewed by Dean Jackson.
+
+        Set the GraphicsLayerPaintOverflowContents phase on the foreground layer in a composited overflow scroller,
+        which prevents clipping to the visible region, fixing scrolling flashes.
+
+        Tested by compositing/overflow/stacking-context-composited-scroller-with-foreground-paint-phases.html
+
+        * rendering/RenderLayerBacking.cpp:
+        (WebCore::RenderLayerBacking::updatePaintingPhases):
+
+2019-06-01  Simon Fraser  <simon.fraser@apple.com>
+
</ins><span class="cx">         Async overflow scroll on iOS paints slowly if it has a negative z-index child
</span><span class="cx">         https://bugs.webkit.org/show_bug.cgi?id=196508
</span><span class="cx">         rdar://problem/49532709
</span></span></pre></div>
<a id="trunkSourceWebCorerenderingRenderLayerBackingcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/rendering/RenderLayerBacking.cpp (246018 => 246019)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/rendering/RenderLayerBacking.cpp    2019-06-02 02:55:57 UTC (rev 246018)
+++ trunk/Source/WebCore/rendering/RenderLayerBacking.cpp       2019-06-02 03:01:47 UTC (rev 246019)
</span><span class="lines">@@ -2102,6 +2102,10 @@
</span><span class="cx">     
</span><span class="cx">     if (m_foregroundLayer) {
</span><span class="cx">         OptionSet<GraphicsLayerPaintingPhase> foregroundLayerPhases { GraphicsLayerPaintingPhase::Foreground };
</span><ins>+        
+        if (m_scrolledContentsLayer)
+            foregroundLayerPhases.add(GraphicsLayerPaintingPhase::OverflowContents);
+
</ins><span class="cx">         m_foregroundLayer->setPaintingPhase(foregroundLayerPhases);
</span><span class="cx">         primaryLayerPhases.remove(GraphicsLayerPaintingPhase::Foreground);
</span><span class="cx">     }
</span></span></pre>
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