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<div id="msg">
<dl class="meta">
<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/245208">245208</a></dd>
<dt>Author</dt> <dd>simon.fraser@apple.com</dd>
<dt>Date</dt> <dd>2019-05-11 15:22:34 -0700 (Sat, 11 May 2019)</dd>
</dl>

<h3>Log Message</h3>
<pre>Layer bounds are incorrect for sharing layers that paint with transforms
https://bugs.webkit.org/show_bug.cgi?id=197768
<rdar://problem/50695493>

Reviewed by Zalan Bujtas.

Source/WebCore:

We don't need to traverse shared layers if the backing-provider has overflow clip,
because we know they are containing-block descendants and therefore clipped.

Note tha the CSS "clip" property doesn't guarantee this, because the clip rect
can be larger than the element, so in that case we just traverse shared layers.

Tests: compositing/shared-backing/sharing-bounds-clip.html
       compositing/shared-backing/sharing-bounds-non-clipping-shared-layer.html
       compositing/shared-backing/sharing-bounds-transformed-sharing-layer.html
       compositing/shared-backing/sharing-bounds.html

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

LayoutTests:

Tests for backing-shared layer bounds in various configurations.

* compositing/shared-backing/sharing-bounds-clip-expected.txt: Added.
* compositing/shared-backing/sharing-bounds-clip.html: Added.
* compositing/shared-backing/sharing-bounds-expected.txt: Added.
* compositing/shared-backing/sharing-bounds-non-clipping-shared-layer-expected.txt: Added.
* compositing/shared-backing/sharing-bounds-non-clipping-shared-layer.html: Added.
* compositing/shared-backing/sharing-bounds-transformed-sharing-layer-expected.txt: Added.
* compositing/shared-backing/sharing-bounds-transformed-sharing-layer.html: Added.
* compositing/shared-backing/sharing-bounds.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="#trunkSourceWebCorerenderingRenderLayerBackingcpp">trunk/Source/WebCore/rendering/RenderLayerBacking.cpp</a></li>
</ul>

<h3>Added Paths</h3>
<ul>
<li><a href="#trunkLayoutTestscompositingsharedbackingsharingboundsclipexpectedtxt">trunk/LayoutTests/compositing/shared-backing/sharing-bounds-clip-expected.txt</a></li>
<li><a href="#trunkLayoutTestscompositingsharedbackingsharingboundscliphtml">trunk/LayoutTests/compositing/shared-backing/sharing-bounds-clip.html</a></li>
<li><a href="#trunkLayoutTestscompositingsharedbackingsharingboundsexpectedtxt">trunk/LayoutTests/compositing/shared-backing/sharing-bounds-expected.txt</a></li>
<li><a href="#trunkLayoutTestscompositingsharedbackingsharingboundsnonclippingsharedlayerexpectedtxt">trunk/LayoutTests/compositing/shared-backing/sharing-bounds-non-clipping-shared-layer-expected.txt</a></li>
<li><a href="#trunkLayoutTestscompositingsharedbackingsharingboundsnonclippingsharedlayerhtml">trunk/LayoutTests/compositing/shared-backing/sharing-bounds-non-clipping-shared-layer.html</a></li>
<li><a href="#trunkLayoutTestscompositingsharedbackingsharingboundstransformedsharinglayerexpectedtxt">trunk/LayoutTests/compositing/shared-backing/sharing-bounds-transformed-sharing-layer-expected.txt</a></li>
<li><a href="#trunkLayoutTestscompositingsharedbackingsharingboundstransformedsharinglayerhtml">trunk/LayoutTests/compositing/shared-backing/sharing-bounds-transformed-sharing-layer.html</a></li>
<li><a href="#trunkLayoutTestscompositingsharedbackingsharingboundshtml">trunk/LayoutTests/compositing/shared-backing/sharing-bounds.html</a></li>
</ul>

</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkLayoutTestsChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/LayoutTests/ChangeLog (245207 => 245208)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/ChangeLog      2019-05-11 22:05:37 UTC (rev 245207)
+++ trunk/LayoutTests/ChangeLog 2019-05-11 22:22:34 UTC (rev 245208)
</span><span class="lines">@@ -1,5 +1,24 @@
</span><span class="cx"> 2019-05-11  Simon Fraser  <simon.fraser@apple.com>
</span><span class="cx"> 
</span><ins>+        Layer bounds are incorrect for sharing layers that paint with transforms
+        https://bugs.webkit.org/show_bug.cgi?id=197768
+        <rdar://problem/50695493>
+
+        Reviewed by Zalan Bujtas.
+
+        Tests for backing-shared layer bounds in various configurations.
+
+        * compositing/shared-backing/sharing-bounds-clip-expected.txt: Added.
+        * compositing/shared-backing/sharing-bounds-clip.html: Added.
+        * compositing/shared-backing/sharing-bounds-expected.txt: Added.
+        * compositing/shared-backing/sharing-bounds-non-clipping-shared-layer-expected.txt: Added.
+        * compositing/shared-backing/sharing-bounds-non-clipping-shared-layer.html: Added.
+        * compositing/shared-backing/sharing-bounds-transformed-sharing-layer-expected.txt: Added.
+        * compositing/shared-backing/sharing-bounds-transformed-sharing-layer.html: Added.
+        * compositing/shared-backing/sharing-bounds.html: Added.
+
+2019-05-11  Simon Fraser  <simon.fraser@apple.com>
+
</ins><span class="cx">         Translucent gradient rendering bug due to will-change transform
</span><span class="cx">         https://bugs.webkit.org/show_bug.cgi?id=197654
</span><span class="cx">         <rdar://problem/50547664>
</span></span></pre></div>
<a id="trunkLayoutTestscompositingsharedbackingsharingboundsclipexpectedtxt"></a>
<div class="addfile"><h4>Added: trunk/LayoutTests/compositing/shared-backing/sharing-bounds-clip-expected.txt (0 => 245208)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/compositing/shared-backing/sharing-bounds-clip-expected.txt                            (rev 0)
+++ trunk/LayoutTests/compositing/shared-backing/sharing-bounds-clip-expected.txt       2019-05-11 22:22:34 UTC (rev 245208)
</span><span class="lines">@@ -0,0 +1,23 @@
</span><ins>+(GraphicsLayer
+  (anchor 0.00 0.00)
+  (bounds 800.00 600.00)
+  (children 1
+    (GraphicsLayer
+      (bounds 800.00 600.00)
+      (contentsOpaque 1)
+      (children 2
+        (GraphicsLayer
+          (position 8.00 8.00)
+          (bounds 50.00 50.00)
+          (contentsOpaque 1)
+        )
+        (GraphicsLayer
+          (position 30.00 30.00)
+          (bounds 500.00 302.00)
+          (drawsContent 1)
+        )
+      )
+    )
+  )
+)
+
</ins></span></pre></div>
<a id="trunkLayoutTestscompositingsharedbackingsharingboundscliphtml"></a>
<div class="addfile"><h4>Added: trunk/LayoutTests/compositing/shared-backing/sharing-bounds-clip.html (0 => 245208)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/compositing/shared-backing/sharing-bounds-clip.html                            (rev 0)
+++ trunk/LayoutTests/compositing/shared-backing/sharing-bounds-clip.html       2019-05-11 22:22:34 UTC (rev 245208)
</span><span class="lines">@@ -0,0 +1,63 @@
</span><ins>+<!DOCTYPE html>
+<html>
+<head>
+    <title>Tests the backing provider layer bounds with a transformed sharing layer</title>
+    <style>
+        .relative {
+            position: absolute;
+            top: 20px;
+            left: 20px;
+            height: 300px;
+            width: 300px;
+            margin: 10px;
+            border: 1px solid black;
+            background-color: silver;
+            clip: rect(10px, 500px, 300px, 10px); /* larger than the bounds */
+        }
+        
+        .sharing {
+                       position: relative;
+                       top: 50px;
+                       left: 50px;
+            width: 200px;
+            height: 200px;
+            background-color: green;
+        }
+        
+        .inner {
+            position: absolute;
+            left: 200px;
+            top: 200px;
+            width: 100px;
+            height: 100px;
+            background-color: blue;
+        }
+
+        .trigger {
+            transform: translateZ(0);
+            width: 50px;
+            height: 50px;
+            background-color: silver;
+        }
+    </style>
+    <script>
+        if (window.testRunner)
+            testRunner.dumpAsText();
+
+        window.addEventListener('load', () => {
+            if (window.internals)
+                document.getElementById('layers').textContent = internals.layerTreeAsText(document);
+        }, false);
+    </script>
+</head>
+<body>
+    <div class="trigger"></div>
+    <div class="relative">
+        <div class="sharing">
+            <div class="inner">
+            </div>
+        </div>
+    </div>
+<pre id="layers"></pre>
+</body>
+</html>
</ins></span></pre></div>
<a id="trunkLayoutTestscompositingsharedbackingsharingboundsexpectedtxt"></a>
<div class="addfile"><h4>Added: trunk/LayoutTests/compositing/shared-backing/sharing-bounds-expected.txt (0 => 245208)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/compositing/shared-backing/sharing-bounds-expected.txt                         (rev 0)
+++ trunk/LayoutTests/compositing/shared-backing/sharing-bounds-expected.txt    2019-05-11 22:22:34 UTC (rev 245208)
</span><span class="lines">@@ -0,0 +1,23 @@
</span><ins>+(GraphicsLayer
+  (anchor 0.00 0.00)
+  (bounds 800.00 600.00)
+  (children 1
+    (GraphicsLayer
+      (bounds 800.00 600.00)
+      (contentsOpaque 1)
+      (children 2
+        (GraphicsLayer
+          (position 8.00 8.00)
+          (bounds 50.00 50.00)
+          (contentsOpaque 1)
+        )
+        (GraphicsLayer
+          (position 30.00 30.00)
+          (bounds 302.00 302.00)
+          (drawsContent 1)
+        )
+      )
+    )
+  )
+)
+
</ins></span></pre></div>
<a id="trunkLayoutTestscompositingsharedbackingsharingboundsnonclippingsharedlayerexpectedtxt"></a>
<div class="addfile"><h4>Added: trunk/LayoutTests/compositing/shared-backing/sharing-bounds-non-clipping-shared-layer-expected.txt (0 => 245208)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/compositing/shared-backing/sharing-bounds-non-clipping-shared-layer-expected.txt                               (rev 0)
+++ trunk/LayoutTests/compositing/shared-backing/sharing-bounds-non-clipping-shared-layer-expected.txt  2019-05-11 22:22:34 UTC (rev 245208)
</span><span class="lines">@@ -0,0 +1,23 @@
</span><ins>+(GraphicsLayer
+  (anchor 0.00 0.00)
+  (bounds 800.00 600.00)
+  (children 1
+    (GraphicsLayer
+      (bounds 800.00 600.00)
+      (contentsOpaque 1)
+      (children 2
+        (GraphicsLayer
+          (position 8.00 8.00)
+          (bounds 50.00 50.00)
+          (contentsOpaque 1)
+        )
+        (GraphicsLayer
+          (position 30.00 30.00)
+          (bounds 501.00 501.00)
+          (drawsContent 1)
+        )
+      )
+    )
+  )
+)
+
</ins></span></pre></div>
<a id="trunkLayoutTestscompositingsharedbackingsharingboundsnonclippingsharedlayerhtml"></a>
<div class="addfile"><h4>Added: trunk/LayoutTests/compositing/shared-backing/sharing-bounds-non-clipping-shared-layer.html (0 => 245208)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/compositing/shared-backing/sharing-bounds-non-clipping-shared-layer.html                               (rev 0)
+++ trunk/LayoutTests/compositing/shared-backing/sharing-bounds-non-clipping-shared-layer.html  2019-05-11 22:22:34 UTC (rev 245208)
</span><span class="lines">@@ -0,0 +1,63 @@
</span><ins>+<!DOCTYPE html>
+<html>
+<head>
+    <title>Tests the backing provider layer bounds with a transformed sharing layer</title>
+    <style>
+        .relative {
+            position: absolute;
+            top: 20px;
+            left: 20px;
+            height: 300px;
+            width: 300px;
+            margin: 10px;
+            border: 1px solid black;
+        }
+        
+        .sharing {
+                       position: relative;
+                       top: 50px;
+                       left: 50px;
+            width: 200px;
+            height: 200px;
+            background-color: green;
+            transform: scale(1.5);
+            transform-origin: top left;
+        }
+        
+        .inner {
+            position: absolute;
+            left: 200px;
+            top: 200px;
+            width: 100px;
+            height: 100px;
+            background-color: blue;
+        }
+
+        .trigger {
+            transform: translateZ(0);
+            width: 50px;
+            height: 50px;
+            background-color: silver;
+        }
+    </style>
+    <script>
+        if (window.testRunner)
+            testRunner.dumpAsText();
+
+        window.addEventListener('load', () => {
+            if (window.internals)
+                document.getElementById('layers').textContent = internals.layerTreeAsText(document);
+        }, false);
+    </script>
+</head>
+<body>
+    <div class="trigger"></div>
+    <div class="relative">
+        <div class="sharing">
+            <div class="inner">
+            </div>
+        </div>
+    </div>
+<pre id="layers"></pre>
+</body>
+</html>
</ins></span></pre></div>
<a id="trunkLayoutTestscompositingsharedbackingsharingboundstransformedsharinglayerexpectedtxt"></a>
<div class="addfile"><h4>Added: trunk/LayoutTests/compositing/shared-backing/sharing-bounds-transformed-sharing-layer-expected.txt (0 => 245208)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/compositing/shared-backing/sharing-bounds-transformed-sharing-layer-expected.txt                               (rev 0)
+++ trunk/LayoutTests/compositing/shared-backing/sharing-bounds-transformed-sharing-layer-expected.txt  2019-05-11 22:22:34 UTC (rev 245208)
</span><span class="lines">@@ -0,0 +1,23 @@
</span><ins>+(GraphicsLayer
+  (anchor 0.00 0.00)
+  (bounds 800.00 600.00)
+  (children 1
+    (GraphicsLayer
+      (bounds 800.00 600.00)
+      (contentsOpaque 1)
+      (children 2
+        (GraphicsLayer
+          (position 8.00 8.00)
+          (bounds 50.00 50.00)
+          (contentsOpaque 1)
+        )
+        (GraphicsLayer
+          (position 30.00 30.00)
+          (bounds 302.00 302.00)
+          (drawsContent 1)
+        )
+      )
+    )
+  )
+)
+
</ins></span></pre></div>
<a id="trunkLayoutTestscompositingsharedbackingsharingboundstransformedsharinglayerhtml"></a>
<div class="addfile"><h4>Added: trunk/LayoutTests/compositing/shared-backing/sharing-bounds-transformed-sharing-layer.html (0 => 245208)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/compositing/shared-backing/sharing-bounds-transformed-sharing-layer.html                               (rev 0)
+++ trunk/LayoutTests/compositing/shared-backing/sharing-bounds-transformed-sharing-layer.html  2019-05-11 22:22:34 UTC (rev 245208)
</span><span class="lines">@@ -0,0 +1,50 @@
</span><ins>+<!DOCTYPE html>
+<html>
+<head>
+    <title>Tests bounds computation for a transformed layer painting into shared backing</title>
+    <style>
+        .clipping {
+            position: absolute;
+            top: 20px;
+            left: 20px;
+            overflow: hidden;
+            height: 300px;
+            width: 300px;
+            margin: 10px;
+            border: 1px solid black;
+        }
+
+        .transformed {
+            width: 400px;
+            height: 100px;
+            background-color: green;
+            transform: scale(2);
+            transform-origin: top left;
+        }
+
+        .trigger {
+            transform: translateZ(0);
+            width: 50px;
+            height: 50px;
+            background-color: silver;
+        }
+    </style>
+    <script>
+        if (window.testRunner)
+            testRunner.dumpAsText();
+
+        window.addEventListener('load', () => {
+            if (window.internals)
+                document.getElementById('layers').textContent = internals.layerTreeAsText(document);
+        }, false);
+    </script>
+</head>
+<body>
+    <div class="trigger"></div>
+    <div class="clipping">
+        <div class="transformed">
+        </div>
+    </div>
+<pre id="layers"></pre>
+</body>
+</html>
</ins></span></pre></div>
<a id="trunkLayoutTestscompositingsharedbackingsharingboundshtml"></a>
<div class="addfile"><h4>Added: trunk/LayoutTests/compositing/shared-backing/sharing-bounds.html (0 => 245208)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/compositing/shared-backing/sharing-bounds.html                         (rev 0)
+++ trunk/LayoutTests/compositing/shared-backing/sharing-bounds.html    2019-05-11 22:22:34 UTC (rev 245208)
</span><span class="lines">@@ -0,0 +1,63 @@
</span><ins>+<!DOCTYPE html>
+<html>
+<head>
+    <title>Tests the backing provider layer bounds with a positioned child</title>
+    <style>
+        .clipping {
+            position: absolute;
+            top: 20px;
+            left: 20px;
+            overflow: hidden;
+            height: 300px;
+            width: 300px;
+            margin: 10px;
+            border: 1px solid black;
+        }
+        
+        .sharing {
+                       position: relative;
+                       top: 50px;
+                       left: 50px;
+            width: 200px;
+            height: 200px;
+            background-color: green;
+        }
+        
+        .inner {
+            position: absolute;
+            left: 200px;
+            top: 200px;
+            width: 100px;
+            height: 100px;
+            background-color: blue;
+        }
+
+        .trigger {
+            transform: translateZ(0);
+            width: 50px;
+            height: 50px;
+            background-color: silver;
+        }
+        
+    </style>
+    <script>
+        if (window.testRunner)
+            testRunner.dumpAsText();
+
+        window.addEventListener('load', () => {
+            if (window.internals)
+                document.getElementById('layers').textContent = internals.layerTreeAsText(document);
+        }, false);
+    </script>
+</head>
+<body>
+    <div class="composited trigger"></div>
+    <div class="clipping">
+        <div class="sharing">
+            <div class="inner">
+            </div>
+        </div>
+    </div>
+<pre id="layers"></pre>
+</body>
+</html>
</ins></span></pre></div>
<a id="trunkSourceWebCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/ChangeLog (245207 => 245208)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/ChangeLog   2019-05-11 22:05:37 UTC (rev 245207)
+++ trunk/Source/WebCore/ChangeLog      2019-05-11 22:22:34 UTC (rev 245208)
</span><span class="lines">@@ -1,5 +1,27 @@
</span><span class="cx"> 2019-05-11  Simon Fraser  <simon.fraser@apple.com>
</span><span class="cx"> 
</span><ins>+        Layer bounds are incorrect for sharing layers that paint with transforms
+        https://bugs.webkit.org/show_bug.cgi?id=197768
+        <rdar://problem/50695493>
+
+        Reviewed by Zalan Bujtas.
+
+        We don't need to traverse shared layers if the backing-provider has overflow clip,
+        because we know they are containing-block descendants and therefore clipped.
+
+        Note tha the CSS "clip" property doesn't guarantee this, because the clip rect
+        can be larger than the element, so in that case we just traverse shared layers.
+
+        Tests: compositing/shared-backing/sharing-bounds-clip.html
+               compositing/shared-backing/sharing-bounds-non-clipping-shared-layer.html
+               compositing/shared-backing/sharing-bounds-transformed-sharing-layer.html
+               compositing/shared-backing/sharing-bounds.html
+
+        * rendering/RenderLayerBacking.cpp:
+        (WebCore::RenderLayerBacking::updateCompositedBounds):
+
+2019-05-11  Simon Fraser  <simon.fraser@apple.com>
+
</ins><span class="cx">         Translucent gradient rendering bug due to will-change transform
</span><span class="cx">         https://bugs.webkit.org/show_bug.cgi?id=197654
</span><span class="cx">         <rdar://problem/50547664>
</span></span></pre></div>
<a id="trunkSourceWebCorerenderingRenderLayerBackingcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/rendering/RenderLayerBacking.cpp (245207 => 245208)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/rendering/RenderLayerBacking.cpp    2019-05-11 22:05:37 UTC (rev 245207)
+++ trunk/Source/WebCore/rendering/RenderLayerBacking.cpp       2019-05-11 22:22:34 UTC (rev 245208)
</span><span class="lines">@@ -671,12 +671,15 @@
</span><span class="cx">         layerBounds.intersect(clippingBounds);
</span><span class="cx">     }
</span><span class="cx"> 
</span><del>-    for (auto& layerWeakPtr : m_backingSharingLayers) {
-        auto* boundsRootLayer = &m_owningLayer;
-        ASSERT(layerWeakPtr->isDescendantOf(m_owningLayer));
-        auto offset = layerWeakPtr->offsetFromAncestor(&m_owningLayer);
-        auto bounds = layerWeakPtr->calculateLayerBounds(boundsRootLayer, offset, RenderLayer::defaultCalculateLayerBoundsFlags() | RenderLayer::ExcludeHiddenDescendants | RenderLayer::DontConstrainForMask);
-        layerBounds.unite(bounds);
</del><ins>+    // If the backing provider has overflow:clip, we know all sharing layers are affected by the clip because they are containing-block descendants.
+    if (!renderer().hasOverflowClip()) {
+        for (auto& layerWeakPtr : m_backingSharingLayers) {
+            auto* boundsRootLayer = &m_owningLayer;
+            ASSERT(layerWeakPtr->isDescendantOf(m_owningLayer));
+            auto offset = layerWeakPtr->offsetFromAncestor(&m_owningLayer);
+            auto bounds = layerWeakPtr->calculateLayerBounds(boundsRootLayer, offset, RenderLayer::defaultCalculateLayerBoundsFlags() | RenderLayer::ExcludeHiddenDescendants | RenderLayer::DontConstrainForMask);
+            layerBounds.unite(bounds);
+        }
</ins><span class="cx">     }
</span><span class="cx"> 
</span><span class="cx">     // If the element has a transform-origin that has fixed lengths, and the renderer has zero size,
</span></span></pre>
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