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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/174367">174367</a></dd>
<dt>Author</dt> <dd>simon.fraser@apple.com</dd>
<dt>Date</dt> <dd>2014-10-06 14:52:42 -0700 (Mon, 06 Oct 2014)</dd>
</dl>
<h3>Log Message</h3>
<pre>Don't attempt to paint into zero-sized backing store
https://bugs.webkit.org/show_bug.cgi?id=137465
Reviewed by Tim Horton.
Page scale could cause the backing store for a small composited element to become empty,
in which case we'd try to allocate, and paint into a graphics context with no surface
behind it.
Fix by bailing from RemoteLayerBackingStore::display() when checking the backing store
size after accounting for scale.
* Shared/mac/RemoteLayerBackingStore.h:
* Shared/mac/RemoteLayerBackingStore.mm:
(WebKit::RemoteLayerBackingStore::backingStoreSize):
(WebKit::RemoteLayerBackingStore::swapToValidFrontBuffer):
(WebKit::RemoteLayerBackingStore::display):</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceWebKit2ChangeLog">trunk/Source/WebKit2/ChangeLog</a></li>
<li><a href="#trunkSourceWebKit2SharedmacRemoteLayerBackingStoreh">trunk/Source/WebKit2/Shared/mac/RemoteLayerBackingStore.h</a></li>
<li><a href="#trunkSourceWebKit2SharedmacRemoteLayerBackingStoremm">trunk/Source/WebKit2/Shared/mac/RemoteLayerBackingStore.mm</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceWebKit2ChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebKit2/ChangeLog (174366 => 174367)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebKit2/ChangeLog 2014-10-06 21:37:28 UTC (rev 174366)
+++ trunk/Source/WebKit2/ChangeLog 2014-10-06 21:52:42 UTC (rev 174367)
</span><span class="lines">@@ -1,3 +1,23 @@
</span><ins>+2014-10-06 Simon Fraser <simon.fraser@apple.com>
+
+ Don't attempt to paint into zero-sized backing store
+ https://bugs.webkit.org/show_bug.cgi?id=137465
+
+ Reviewed by Tim Horton.
+
+ Page scale could cause the backing store for a small composited element to become empty,
+ in which case we'd try to allocate, and paint into a graphics context with no surface
+ behind it.
+
+ Fix by bailing from RemoteLayerBackingStore::display() when checking the backing store
+ size after accounting for scale.
+
+ * Shared/mac/RemoteLayerBackingStore.h:
+ * Shared/mac/RemoteLayerBackingStore.mm:
+ (WebKit::RemoteLayerBackingStore::backingStoreSize):
+ (WebKit::RemoteLayerBackingStore::swapToValidFrontBuffer):
+ (WebKit::RemoteLayerBackingStore::display):
+
</ins><span class="cx"> 2014-10-06 Christophe Dumez <cdumez@apple.com>
</span><span class="cx">
</span><span class="cx"> Use is<>() / downcast<>() for ScrollingTree subclasses
</span></span></pre></div>
<a id="trunkSourceWebKit2SharedmacRemoteLayerBackingStoreh"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebKit2/Shared/mac/RemoteLayerBackingStore.h (174366 => 174367)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebKit2/Shared/mac/RemoteLayerBackingStore.h 2014-10-06 21:37:28 UTC (rev 174366)
+++ trunk/Source/WebKit2/Shared/mac/RemoteLayerBackingStore.h 2014-10-06 21:52:42 UTC (rev 174367)
</span><span class="lines">@@ -96,6 +96,8 @@
</span><span class="cx"> void drawInContext(WebCore::GraphicsContext&, CGImageRef backImage);
</span><span class="cx"> void clearBackingStore();
</span><span class="cx"> void swapToValidFrontBuffer();
</span><ins>+
+ WebCore::IntSize backingStoreSize() const;
</ins><span class="cx">
</span><span class="cx"> PlatformCALayerRemote* m_layer;
</span><span class="cx">
</span></span></pre></div>
<a id="trunkSourceWebKit2SharedmacRemoteLayerBackingStoremm"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebKit2/Shared/mac/RemoteLayerBackingStore.mm (174366 => 174367)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebKit2/Shared/mac/RemoteLayerBackingStore.mm 2014-10-06 21:37:28 UTC (rev 174366)
+++ trunk/Source/WebKit2/Shared/mac/RemoteLayerBackingStore.mm 2014-10-06 21:52:42 UTC (rev 174367)
</span><span class="lines">@@ -171,12 +171,17 @@
</span><span class="cx"> setNeedsDisplay(IntRect(IntPoint(), expandedIntSize(m_size)));
</span><span class="cx"> }
</span><span class="cx">
</span><del>-void RemoteLayerBackingStore::swapToValidFrontBuffer()
</del><ins>+IntSize RemoteLayerBackingStore::backingStoreSize() const
</ins><span class="cx"> {
</span><span class="cx"> FloatSize scaledSize = m_size;
</span><span class="cx"> scaledSize.scale(m_scale);
</span><del>- IntSize expandedScaledSize = roundedIntSize(scaledSize);
</del><ins>+ return roundedIntSize(scaledSize);
+}
</ins><span class="cx">
</span><ins>+void RemoteLayerBackingStore::swapToValidFrontBuffer()
+{
+ IntSize expandedScaledSize = backingStoreSize();
+
</ins><span class="cx"> #if USE(IOSURFACE)
</span><span class="cx"> if (m_acceleratesDrawing) {
</span><span class="cx"> if (!m_backBuffer.surface || m_backBuffer.surface->isInUse()) {
</span><span class="lines">@@ -215,7 +220,9 @@
</span><span class="cx"> // Make the previous front buffer non-volatile early, so that we can dirty the whole layer if it comes back empty.
</span><span class="cx"> setBufferVolatility(BufferType::Front, false);
</span><span class="cx">
</span><del>- if (m_dirtyRegion.isEmpty() || m_size.isEmpty())
</del><ins>+ IntSize expandedScaledSize = backingStoreSize();
+
+ if (m_dirtyRegion.isEmpty() || expandedScaledSize.isEmpty())
</ins><span class="cx"> return false;
</span><span class="cx">
</span><span class="cx"> IntRect layerBounds(IntPoint(), expandedIntSize(m_size));
</span><span class="lines">@@ -227,9 +234,6 @@
</span><span class="cx"> m_dirtyRegion.unite(indicatorRect);
</span><span class="cx"> }
</span><span class="cx">
</span><del>- FloatSize scaledSize = m_size;
- scaledSize.scale(m_scale);
- IntSize expandedScaledSize = roundedIntSize(scaledSize);
</del><span class="cx"> IntRect expandedScaledLayerBounds(IntPoint(), expandedScaledSize);
</span><span class="cx"> bool willPaintEntireBackingStore = m_dirtyRegion.contains(layerBounds);
</span><span class="cx">
</span></span></pre>
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