<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
"http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head><meta http-equiv="content-type" content="text/html; charset=utf-8" />
<title>[286441] trunk</title>
</head>
<body>

<style type="text/css"><!--
#msg dl.meta { border: 1px #006 solid; background: #369; padding: 6px; color: #fff; }
#msg dl.meta dt { float: left; width: 6em; font-weight: bold; }
#msg dt:after { content:':';}
#msg dl, #msg dt, #msg ul, #msg li, #header, #footer, #logmsg { font-family: verdana,arial,helvetica,sans-serif; font-size: 10pt;  }
#msg dl a { font-weight: bold}
#msg dl a:link    { color:#fc3; }
#msg dl a:active  { color:#ff0; }
#msg dl a:visited { color:#cc6; }
h3 { font-family: verdana,arial,helvetica,sans-serif; font-size: 10pt; font-weight: bold; }
#msg pre { overflow: auto; background: #ffc; border: 1px #fa0 solid; padding: 6px; }
#logmsg { background: #ffc; border: 1px #fa0 solid; padding: 1em 1em 0 1em; }
#logmsg p, #logmsg pre, #logmsg blockquote { margin: 0 0 1em 0; }
#logmsg p, #logmsg li, #logmsg dt, #logmsg dd { line-height: 14pt; }
#logmsg h1, #logmsg h2, #logmsg h3, #logmsg h4, #logmsg h5, #logmsg h6 { margin: .5em 0; }
#logmsg h1:first-child, #logmsg h2:first-child, #logmsg h3:first-child, #logmsg h4:first-child, #logmsg h5:first-child, #logmsg h6:first-child { margin-top: 0; }
#logmsg ul, #logmsg ol { padding: 0; list-style-position: inside; margin: 0 0 0 1em; }
#logmsg ul { text-indent: -1em; padding-left: 1em; }#logmsg ol { text-indent: -1.5em; padding-left: 1.5em; }
#logmsg > ul, #logmsg > ol { margin: 0 0 1em 0; }
#logmsg pre { background: #eee; padding: 1em; }
#logmsg blockquote { border: 1px solid #fa0; border-left-width: 10px; padding: 1em 1em 0 1em; background: white;}
#logmsg dl { margin: 0; }
#logmsg dt { font-weight: bold; }
#logmsg dd { margin: 0; padding: 0 0 0.5em 0; }
#logmsg dd:before { content:'\00bb';}
#logmsg table { border-spacing: 0px; border-collapse: collapse; border-top: 4px solid #fa0; border-bottom: 1px solid #fa0; background: #fff; }
#logmsg table th { text-align: left; font-weight: normal; padding: 0.2em 0.5em; border-top: 1px dotted #fa0; }
#logmsg table td { text-align: right; border-top: 1px dotted #fa0; padding: 0.2em 0.5em; }
#logmsg table thead th { text-align: center; border-bottom: 1px solid #fa0; }
#logmsg table th.Corner { text-align: left; }
#logmsg hr { border: none 0; border-top: 2px dashed #fa0; height: 1px; }
#header, #footer { color: #fff; background: #636; border: 1px #300 solid; padding: 6px; }
#patch { width: 100%; }
#patch h4 {font-family: verdana,arial,helvetica,sans-serif;font-size:10pt;padding:8px;background:#369;color:#fff;margin:0;}
#patch .propset h4, #patch .binary h4 {margin:0;}
#patch pre {padding:0;line-height:1.2em;margin:0;}
#patch .diff {width:100%;background:#eee;padding: 0 0 10px 0;overflow:auto;}
#patch .propset .diff, #patch .binary .diff  {padding:10px 0;}
#patch span {display:block;padding:0 10px;}
#patch .modfile, #patch .addfile, #patch .delfile, #patch .propset, #patch .binary, #patch .copfile {border:1px solid #ccc;margin:10px 0;}
#patch ins {background:#dfd;text-decoration:none;display:block;padding:0 10px;}
#patch del {background:#fdd;text-decoration:none;display:block;padding:0 10px;}
#patch .lines, .info {color:#888;background:#fff;}
--></style>
<div id="msg">
<dl class="meta">
<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/286441">286441</a></dd>
<dt>Author</dt> <dd>ryanhaddad@apple.com</dd>
<dt>Date</dt> <dd>2021-12-02 11:49:47 -0800 (Thu, 02 Dec 2021)</dd>
</dl>

<h3>Log Message</h3>
<pre>Fix crash in GraphicsContextCG::endTransparencyLayer
https://bugs.webkit.org/show_bug.cgi?id=230230

Patch by Tim Nguyen <ntim@apple.com> on 2021-12-02
Reviewed by Myles C. Maxfield.

Source/WebCore:

The crash was due to unbalanced calls to begin and end transparency layers.

A branch handling ancestors of transparent layers that are transform root needed to be
aware of the top layer. Opacity on ancestors don't affect top layer elements so calling
`beginTransparencyLayers` on `parent()` is incorrect.

Also fix `transparentPaintingAncestor()` to be top layer aware to avoid flickering layers
while scrolling.

Test: fast/layers/top-layer-ancestor-opacity-and-transform-crash.html

* rendering/RenderLayer.cpp:
(WebCore::RenderLayer::transparentPaintingAncestor):
(WebCore::RenderLayer::paintLayerWithEffects):

LayoutTests:

* fast/layers/top-layer-ancestor-opacity-and-transform-crash-expected.txt: Added.
* fast/layers/top-layer-ancestor-opacity-and-transform-crash.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="#trunkSourceWebCorerenderingRenderLayercpp">trunk/Source/WebCore/rendering/RenderLayer.cpp</a></li>
</ul>

<h3>Added Paths</h3>
<ul>
<li><a href="#trunkLayoutTestsfastlayerstoplayerancestoropacityandtransformcrashexpectedtxt">trunk/LayoutTests/fast/layers/top-layer-ancestor-opacity-and-transform-crash-expected.txt</a></li>
<li><a href="#trunkLayoutTestsfastlayerstoplayerancestoropacityandtransformcrashhtml">trunk/LayoutTests/fast/layers/top-layer-ancestor-opacity-and-transform-crash.html</a></li>
</ul>

</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkLayoutTestsChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/LayoutTests/ChangeLog (286440 => 286441)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/ChangeLog      2021-12-02 19:39:41 UTC (rev 286440)
+++ trunk/LayoutTests/ChangeLog 2021-12-02 19:49:47 UTC (rev 286441)
</span><span class="lines">@@ -1,3 +1,13 @@
</span><ins>+2021-12-02  Tim Nguyen  <ntim@apple.com>
+
+        Fix crash in GraphicsContextCG::endTransparencyLayer
+        https://bugs.webkit.org/show_bug.cgi?id=230230
+
+        Reviewed by Myles C. Maxfield.
+
+        * fast/layers/top-layer-ancestor-opacity-and-transform-crash-expected.txt: Added.
+        * fast/layers/top-layer-ancestor-opacity-and-transform-crash.html: Added.
+
</ins><span class="cx"> 2021-12-02  Robert Jenner  <Jenner@apple.com>
</span><span class="cx"> 
</span><span class="cx">         Unreviewed, reverting r285570.
</span></span></pre></div>
<a id="trunkLayoutTestsfastlayerstoplayerancestoropacityandtransformcrashexpectedtxt"></a>
<div class="addfile"><h4>Added: trunk/LayoutTests/fast/layers/top-layer-ancestor-opacity-and-transform-crash-expected.txt (0 => 286441)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/fast/layers/top-layer-ancestor-opacity-and-transform-crash-expected.txt                                (rev 0)
+++ trunk/LayoutTests/fast/layers/top-layer-ancestor-opacity-and-transform-crash-expected.txt   2021-12-02 19:49:47 UTC (rev 286441)
</span><span class="lines">@@ -0,0 +1 @@
</span><ins>+PASS if this doesn't crash
</ins></span></pre></div>
<a id="trunkLayoutTestsfastlayerstoplayerancestoropacityandtransformcrashhtml"></a>
<div class="addfile"><h4>Added: trunk/LayoutTests/fast/layers/top-layer-ancestor-opacity-and-transform-crash.html (0 => 286441)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/fast/layers/top-layer-ancestor-opacity-and-transform-crash.html                                (rev 0)
+++ trunk/LayoutTests/fast/layers/top-layer-ancestor-opacity-and-transform-crash.html   2021-12-02 19:49:47 UTC (rev 286441)
</span><span class="lines">@@ -0,0 +1,9 @@
</span><ins>+<style>
+* { opacity: 0.1; translate: 1px; }
+</style>
+<dialog>PASS if this doesn't crash</dialog>
+<script>
+    document.querySelector("dialog").showModal();
+    if (testRunner)
+        testRunner.dumpAsText();
+</script>
</ins></span></pre></div>
<a id="trunkSourceWebCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/ChangeLog (286440 => 286441)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/ChangeLog   2021-12-02 19:39:41 UTC (rev 286440)
+++ trunk/Source/WebCore/ChangeLog      2021-12-02 19:49:47 UTC (rev 286441)
</span><span class="lines">@@ -1,3 +1,25 @@
</span><ins>+2021-12-02  Tim Nguyen  <ntim@apple.com>
+
+        Fix crash in GraphicsContextCG::endTransparencyLayer
+        https://bugs.webkit.org/show_bug.cgi?id=230230
+
+        Reviewed by Myles C. Maxfield.
+
+        The crash was due to unbalanced calls to begin and end transparency layers.
+
+        A branch handling ancestors of transparent layers that are transform root needed to be
+        aware of the top layer. Opacity on ancestors don't affect top layer elements so calling
+        `beginTransparencyLayers` on `parent()` is incorrect.
+
+        Also fix `transparentPaintingAncestor()` to be top layer aware to avoid flickering layers
+        while scrolling.
+
+        Test: fast/layers/top-layer-ancestor-opacity-and-transform-crash.html
+
+        * rendering/RenderLayer.cpp:
+        (WebCore::RenderLayer::transparentPaintingAncestor):
+        (WebCore::RenderLayer::paintLayerWithEffects):
+
</ins><span class="cx"> 2021-12-02  Robert Jenner  <Jenner@apple.com>
</span><span class="cx"> 
</span><span class="cx">         Unreviewed, reverting r285570.
</span></span></pre></div>
<a id="trunkSourceWebCorerenderingRenderLayercpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/rendering/RenderLayer.cpp (286440 => 286441)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/rendering/RenderLayer.cpp   2021-12-02 19:39:41 UTC (rev 286440)
+++ trunk/Source/WebCore/rendering/RenderLayer.cpp      2021-12-02 19:49:47 UTC (rev 286441)
</span><span class="lines">@@ -2089,9 +2089,9 @@
</span><span class="cx">     if (isComposited())
</span><span class="cx">         return nullptr;
</span><span class="cx"> 
</span><del>-    for (RenderLayer* curr = parent(); curr; curr = curr->parent()) {
</del><ins>+    for (RenderLayer* curr = stackingContext(); curr; curr = curr->stackingContext()) {
</ins><span class="cx">         if (curr->isComposited())
</span><del>-            return nullptr;
</del><ins>+            break;
</ins><span class="cx">         if (curr->isTransparent())
</span><span class="cx">             return curr;
</span><span class="cx">     }
</span><span class="lines">@@ -3061,7 +3061,8 @@
</span><span class="cx">         // If we have a transparency layer enclosing us and we are the root of a transform, then we need to establish the transparency
</span><span class="cx">         // layer from the parent now, assuming there is a parent
</span><span class="cx">         if (paintFlags & PaintLayerFlag::HaveTransparency) {
</span><del>-            if (parent())
</del><ins>+            // Top layer elements are not affected by ancestor opacities
+            if (!establishesTopLayer() && parent())
</ins><span class="cx">                 parent()->beginTransparencyLayers(context, paintingInfo, paintingInfo.paintDirtyRect);
</span><span class="cx">             else
</span><span class="cx">                 beginTransparencyLayers(context, paintingInfo, paintingInfo.paintDirtyRect);
</span></span></pre>
</div>
</div>

</body>
</html>