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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/281839">281839</a></dd>
<dt>Author</dt> <dd>said@apple.com</dd>
<dt>Date</dt> <dd>2021-09-01 00:55:39 -0700 (Wed, 01 Sep 2021)</dd>
</dl>

<h3>Log Message</h3>
<pre>[GPU Process](REGRESSION): A detached canvas leaks all the images it draws
https://bugs.webkit.org/show_bug.cgi?id=229668
<rdar://problem/82532484>

Reviewed by Simon Fraser.

Before drawing the canvas to the page, the canvas element may need to
prepare its context for display. For 2D canvas elements, this should
happen regardless whether they are attached to the Document or not.
Because prepareForDisplay() calls ImageBuffer::flushDrawingContextAsync(),
this will ensure the canvas drawing commands are pushed from WebProcess
to GPUProcess. It will also release the cached shared images from both
WebProcess and GPUProcess.

Move the decision to skip the context prepareForDisplay() step from
Document::prepareCanvasesForDisplayIfNeeded() to
WebGLRenderingContextBase::prepareForDisplay().

* dom/Document.cpp:
(WebCore::Document::prepareCanvasesForDisplayIfNeeded):
* html/canvas/WebGLRenderingContextBase.cpp:
(WebCore::WebGLRenderingContextBase::prepareForDisplay):</pre>

<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceWebCoreChangeLog">trunk/Source/WebCore/ChangeLog</a></li>
<li><a href="#trunkSourceWebCoredomDocumentcpp">trunk/Source/WebCore/dom/Document.cpp</a></li>
<li><a href="#trunkSourceWebCorehtmlcanvasWebGLRenderingContextBasecpp">trunk/Source/WebCore/html/canvas/WebGLRenderingContextBase.cpp</a></li>
</ul>

</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceWebCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/ChangeLog (281838 => 281839)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/ChangeLog   2021-09-01 05:24:30 UTC (rev 281838)
+++ trunk/Source/WebCore/ChangeLog      2021-09-01 07:55:39 UTC (rev 281839)
</span><span class="lines">@@ -1,3 +1,28 @@
</span><ins>+2021-09-01  Said Abou-Hallawa  <said@apple.com>
+
+        [GPU Process](REGRESSION): A detached canvas leaks all the images it draws
+        https://bugs.webkit.org/show_bug.cgi?id=229668
+        <rdar://problem/82532484>
+
+        Reviewed by Simon Fraser.
+
+        Before drawing the canvas to the page, the canvas element may need to 
+        prepare its context for display. For 2D canvas elements, this should 
+        happen regardless whether they are attached to the Document or not.
+        Because prepareForDisplay() calls ImageBuffer::flushDrawingContextAsync(),
+        this will ensure the canvas drawing commands are pushed from WebProcess
+        to GPUProcess. It will also release the cached shared images from both
+        WebProcess and GPUProcess.
+
+        Move the decision to skip the context prepareForDisplay() step from 
+        Document::prepareCanvasesForDisplayIfNeeded() to 
+        WebGLRenderingContextBase::prepareForDisplay().
+
+        * dom/Document.cpp:
+        (WebCore::Document::prepareCanvasesForDisplayIfNeeded):
+        * html/canvas/WebGLRenderingContextBase.cpp:
+        (WebCore::WebGLRenderingContextBase::prepareForDisplay):
+
</ins><span class="cx"> 2021-08-31  Lauro Moura  <lmoura@igalia.com>
</span><span class="cx"> 
</span><span class="cx">         Non-unified build partial fixes, late late August 2021
</span></span></pre></div>
<a id="trunkSourceWebCoredomDocumentcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/dom/Document.cpp (281838 => 281839)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/dom/Document.cpp    2021-09-01 05:24:30 UTC (rev 281838)
+++ trunk/Source/WebCore/dom/Document.cpp       2021-09-01 07:55:39 UTC (rev 281839)
</span><span class="lines">@@ -8933,15 +8933,8 @@
</span><span class="cx"> 
</span><span class="cx">     auto canvases = copyToVectorOf<Ref<HTMLCanvasElement>>(m_canvasesNeedingDisplayPreparation);
</span><span class="cx">     m_canvasesNeedingDisplayPreparation.clear();
</span><del>-    for (auto& canvas : canvases) {
-        // However, if they are not in the document body, then they won't
-        // be composited and thus don't need preparation. Unfortunately they
-        // can't tell at the time they were added to the list, since they
-        // could be inserted or removed from the document body afterwards.
-        if (!canvas->isInTreeScope())
-            continue;
</del><ins>+    for (auto& canvas : canvases)
</ins><span class="cx">         canvas->prepareForDisplay();
</span><del>-    }
</del><span class="cx"> }
</span><span class="cx"> 
</span><span class="cx"> void Document::clearCanvasPreparation(HTMLCanvasElement& canvas)
</span></span></pre></div>
<a id="trunkSourceWebCorehtmlcanvasWebGLRenderingContextBasecpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/html/canvas/WebGLRenderingContextBase.cpp (281838 => 281839)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/html/canvas/WebGLRenderingContextBase.cpp   2021-09-01 05:24:30 UTC (rev 281838)
+++ trunk/Source/WebCore/html/canvas/WebGLRenderingContextBase.cpp      2021-09-01 07:55:39 UTC (rev 281839)
</span><span class="lines">@@ -8159,6 +8159,14 @@
</span><span class="cx">     if (!m_context)
</span><span class="cx">         return;
</span><span class="cx"> 
</span><ins>+    // If the canvas is not in the document body, then it won't be
+    // composited and thus doesn't need preparation. Unfortunately
+    // it can't tell at the time it was added to the list, since it
+    // could be inserted or removed from the document body afterwards.
+    auto canvas = htmlCanvas();
+    if (!canvas || !canvas->isInTreeScope())
+        return;
+
</ins><span class="cx">     m_context->prepareForDisplay();
</span><span class="cx"> }
</span><span class="cx"> 
</span></span></pre>
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