Changeset 174367 in webkit

Timestamp:

Oct 6, 2014 2:52:42 PM (10 years ago)

Author:

Simon Fraser

Message:

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):

Location:

trunk/Source/WebKit2

Files:

• ChangeLog (modified) (1 diff)
• Shared/mac/RemoteLayerBackingStore.h (modified) (1 diff)
• Shared/mac/RemoteLayerBackingStore.mm (modified) (3 diffs)

trunk/Source/WebKit2/ChangeLog

@@ +1 @@
+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):
+
 2014-10-06  Christophe Dumez  <cdumez@apple.com>
 

trunk/Source/WebKit2/Shared/mac/RemoteLayerBackingStore.h

@@ -97 +97 @@
     void clearBackingStore();
     void swapToValidFrontBuffer();
+    
+    WebCore::IntSize backingStoreSize() const;
 
     PlatformCALayerRemote* m_layer;

trunk/Source/WebKit2/Shared/mac/RemoteLayerBackingStore.mm

@@ -172 +172 @@
 }
 
-void RemoteLayerBackingStore::swapToValidFrontBuffer()
+IntSize RemoteLayerBackingStore::backingStoreSize() const
 {
     FloatSize scaledSize = m_size;
     scaledSize.scale(m_scale);
-    IntSize expandedScaledSize = roundedIntSize(scaledSize);
+    return roundedIntSize(scaledSize);
+}
+
+void RemoteLayerBackingStore::swapToValidFrontBuffer()
+{
+    IntSize expandedScaledSize = backingStoreSize();
 
 #if USE(IOSURFACE)
@@ -216 +221 @@
     setBufferVolatility(BufferType::Front, false);
 
-    if (m_dirtyRegion.isEmpty() || m_size.isEmpty())
+    IntSize expandedScaledSize = backingStoreSize();
+
+    if (m_dirtyRegion.isEmpty() || expandedScaledSize.isEmpty())
         return false;
 
@@ -228 +235 @@
     }
 
-    FloatSize scaledSize = m_size;
-    scaledSize.scale(m_scale);
-    IntSize expandedScaledSize = roundedIntSize(scaledSize);
     IntRect expandedScaledLayerBounds(IntPoint(), expandedScaledSize);
     bool willPaintEntireBackingStore = m_dirtyRegion.contains(layerBounds);