Ensure replaced tiles are repainted

If a layer with a backing store is resized, we may replace some tiles
that were not at maximum size. When that happens we need to ensure the
replaced area is repainted, otherwise the content disappears until
refreshed.

Change-Id: Ie2f7796a2493a56ed5fc6cc4cea55f4ab9f38bbe
Reviewed-by: Michael Bruning <michael.bruning@digia.com>

2 files changed, 13 insertions, 8 deletions

diff --git a/Source/WebCore/platform/graphics/texmap/TextureMapperTiledBackingStore.cpp b/Source/WebCore/platform/graphics/texmap/TextureMapperTiledBackingStore.cpp
index ef564023d..801a2d46f 100644
--- a/Source/WebCore/platform/graphics/texmap/TextureMapperTiledBackingStore.cpp
+++ b/Source/WebCore/platform/graphics/texmap/TextureMapperTiledBackingStore.cpp
@@ -69,11 +69,10 @@ void TextureMapperTiledBackingStore::drawRepaintCounter(TextureMapper* textureMa
         textureMapper->drawNumber(repaintCount, borderColor, m_tiles[i].rect().location(), adjustedTransform);
 }
 
-void TextureMapperTiledBackingStore::createOrDestroyTilesIfNeeded(const FloatSize& size, const IntSize& tileSize, bool hasAlpha)
+void TextureMapperTiledBackingStore::createOrDestroyTilesIfNeeded(const FloatSize& size, const IntSize& tileSize, bool hasAlpha, IntRect& repaintRect)
 {
     if (size == m_size)
         return;
-
     m_size = size;
 
     Vector<FloatRect> tileRectsToAdd;
@@ -107,8 +106,12 @@ void TextureMapperTiledBackingStore::createOrDestroyTilesIfNeeded(const FloatSiz
         }
 
         // This tile is not needed.
-        if (!existsAlready)
+        if (!existsAlready) {
             tileIndicesToRemove.append(i);
+            // If the removed tile was painted ensure the area it covered is repainted.
+            if (m_tiles[i].texture())
+                repaintRect.unite(enclosingIntRect(oldTile));
+        }
     }
 
     // Recycle removable tiles to be used for newly requested tiles.
@@ -135,16 +138,18 @@ void TextureMapperTiledBackingStore::createOrDestroyTilesIfNeeded(const FloatSiz
 
 void TextureMapperTiledBackingStore::updateContents(TextureMapper* textureMapper, Image* image, const FloatSize& totalSize, const IntRect& dirtyRect, BitmapTexture::UpdateContentsFlag updateContentsFlag)
 {
-    createOrDestroyTilesIfNeeded(totalSize, textureMapper->maxTextureSize(), !image->currentFrameKnownToBeOpaque());
+    IntRect repaintRect(dirtyRect);
+    createOrDestroyTilesIfNeeded(totalSize, textureMapper->maxTextureSize(), !image->currentFrameKnownToBeOpaque(), repaintRect);
     for (size_t i = 0; i < m_tiles.size(); ++i)
-        m_tiles[i].updateContents(textureMapper, image, dirtyRect, updateContentsFlag);
+        m_tiles[i].updateContents(textureMapper, image, repaintRect, updateContentsFlag);
 }
 
 void TextureMapperTiledBackingStore::updateContents(TextureMapper* textureMapper, GraphicsLayer* sourceLayer, const FloatSize& totalSize, const IntRect& dirtyRect, BitmapTexture::UpdateContentsFlag updateContentsFlag)
 {
-    createOrDestroyTilesIfNeeded(totalSize, textureMapper->maxTextureSize(), true);
+    IntRect repaintRect(dirtyRect);
+    createOrDestroyTilesIfNeeded(totalSize, textureMapper->maxTextureSize(), true, repaintRect);
     for (size_t i = 0; i < m_tiles.size(); ++i)
-        m_tiles[i].updateContents(textureMapper, sourceLayer, dirtyRect, updateContentsFlag);
+        m_tiles[i].updateContents(textureMapper, sourceLayer, repaintRect, updateContentsFlag);
 }
 
 PassRefPtr<BitmapTexture> TextureMapperTiledBackingStore::texture() const
diff --git a/Source/WebCore/platform/graphics/texmap/TextureMapperTiledBackingStore.h b/Source/WebCore/platform/graphics/texmap/TextureMapperTiledBackingStore.h
index 9b8568463..6a44b68ae 100644
--- a/Source/WebCore/platform/graphics/texmap/TextureMapperTiledBackingStore.h
+++ b/Source/WebCore/platform/graphics/texmap/TextureMapperTiledBackingStore.h
@@ -48,7 +48,7 @@ public:
 
 private:
     TextureMapperTiledBackingStore();
-    void createOrDestroyTilesIfNeeded(const FloatSize& backingStoreSize, const IntSize& tileSize, bool hasAlpha);
+    void createOrDestroyTilesIfNeeded(const FloatSize& backingStoreSize, const IntSize& tileSize, bool hasAlpha, IntRect&);
     void updateContentsFromImageIfNeeded(TextureMapper*);
     TransformationMatrix adjustedTransformForRect(const FloatRect&);
     inline FloatRect rect() const { return FloatRect(FloatPoint::zero(), m_size); }