Coordinated Graphics: a long page is scaled vertically while loading.

https://bugs.webkit.org/show_bug.cgi?id=109645

Backported from http://trac.webkit.org/changeset/142837

Reviewed by Noam Rosenthal.

When loading http://www.w3.org/TR/xpath-datamodel/, Coordinated Graphics draws
vertically scaled contents. It is because there is the difference between the
size of a layer and the size of CoordinatedBackingStore.

Currently, LayerTreeRenderer notifies the size to CoordinatedBackingStore
at the moment of creating, updating and removing a tile. However, it is not
necessary to send tile-related messages when the size of layer is changed.
So this patch resets the size of CoordinatedBackingStore when receiving the
message that is created when the size is changed: SyncLayerState.

There is no current way to reliably test flicker issues.

Change-Id: Ied0dfa7e333b0c7d89c33684b05ca9e1dfebd155
Reviewed-by: Jocelyn Turcotte <jocelyn.turcotte@digia.com>

3 files changed, 10 insertions, 5 deletions

diff --git a/Source/WebKit2/UIProcess/CoordinatedGraphics/CoordinatedBackingStore.cpp b/Source/WebKit2/UIProcess/CoordinatedGraphics/CoordinatedBackingStore.cpp
index 4c0ced289..17c18bd1a 100644
--- a/Source/WebKit2/UIProcess/CoordinatedGraphics/CoordinatedBackingStore.cpp
+++ b/Source/WebKit2/UIProcess/CoordinatedGraphics/CoordinatedBackingStore.cpp
@@ -106,7 +106,7 @@ PassRefPtr<BitmapTexture> CoordinatedBackingStore::texture() const
 
 void CoordinatedBackingStore::setSize(const WebCore::FloatSize& size)
 {
-    m_size = size;
+    m_pendingSize = size;
 }
 
 static bool shouldShowTileDebugVisuals()
@@ -177,6 +177,11 @@ void CoordinatedBackingStore::paintToTextureMapper(TextureMapper* textureMapper,
 void CoordinatedBackingStore::commitTileOperations(TextureMapper* textureMapper)
 {
     HashSet<int>::iterator tilesToRemoveEnd = m_tilesToRemove.end();
+    if (!m_pendingSize.isZero()) {
+        m_size = m_pendingSize;
+        m_pendingSize = FloatSize();
+    }
+
     for (HashSet<int>::iterator it = m_tilesToRemove.begin(); it != tilesToRemoveEnd; ++it)
         m_tiles.remove(*it);
     m_tilesToRemove.clear();
diff --git a/Source/WebKit2/UIProcess/CoordinatedGraphics/CoordinatedBackingStore.h b/Source/WebKit2/UIProcess/CoordinatedGraphics/CoordinatedBackingStore.h
index 4038a3724..3b747372d 100644
--- a/Source/WebKit2/UIProcess/CoordinatedGraphics/CoordinatedBackingStore.h
+++ b/Source/WebKit2/UIProcess/CoordinatedGraphics/CoordinatedBackingStore.h
@@ -77,6 +77,8 @@ private:
     HashSet<int> m_tilesToRemove;
     WebCore::FloatSize m_size;
     float m_scale;
+    // FIXME: m_pendingSize should be removed after the following bug is fixed: https://bugs.webkit.org/show_bug.cgi?id=108294
+    WebCore::FloatSize m_pendingSize;
 };
 
 } // namespace WebKit
diff --git a/Source/WebKit2/UIProcess/CoordinatedGraphics/LayerTreeRenderer.cpp b/Source/WebKit2/UIProcess/CoordinatedGraphics/LayerTreeRenderer.cpp
index 0e88379bf..6ed1b12fd 100644
--- a/Source/WebKit2/UIProcess/CoordinatedGraphics/LayerTreeRenderer.cpp
+++ b/Source/WebKit2/UIProcess/CoordinatedGraphics/LayerTreeRenderer.cpp
@@ -427,6 +427,7 @@ void LayerTreeRenderer::prepareContentBackingStore(GraphicsLayer* graphicsLayer)
     }
 
     createBackingStoreIfNeeded(graphicsLayer);
+    resetBackingStoreSizeToLayerSize(graphicsLayer);
 }
 
 void LayerTreeRenderer::createBackingStoreIfNeeded(GraphicsLayer* graphicsLayer)
@@ -448,7 +449,6 @@ void LayerTreeRenderer::createBackingStoreIfNeeded(GraphicsLayer* graphicsLayer)
         return; // The layer already has a backing store (and no pending removal).
 
     RefPtr<CoordinatedBackingStore> backingStore(CoordinatedBackingStore::create());
-    backingStore->setSize(graphicsLayer->size());
     ASSERT(!m_pendingSyncBackingStores.contains(layer));
     m_pendingSyncBackingStores.add(layer, backingStore);
 }
@@ -481,6 +481,7 @@ void LayerTreeRenderer::resetBackingStoreSizeToLayerSize(GraphicsLayer* graphics
     CoordinatedBackingStore* backingStore = getBackingStore(graphicsLayer);
     ASSERT(backingStore);
     backingStore->setSize(graphicsLayer->size());
+    m_backingStoresWithPendingBuffers.add(backingStore);
 }
 
 void LayerTreeRenderer::createTile(WebLayerID layerID, int tileID, float scale)
@@ -490,7 +491,6 @@ void LayerTreeRenderer::createTile(WebLayerID layerID, int tileID, float scale)
     CoordinatedBackingStore* backingStore = getBackingStore(layer);
     ASSERT(backingStore);
     backingStore->createTile(tileID, scale);
-    resetBackingStoreSizeToLayerSize(layer);
 }
 
 void LayerTreeRenderer::removeTile(WebLayerID layerID, int tileID)
@@ -502,7 +502,6 @@ void LayerTreeRenderer::removeTile(WebLayerID layerID, int tileID)
         return;
 
     backingStore->removeTile(tileID);
-    resetBackingStoreSizeToLayerSize(layer);
     m_backingStoresWithPendingBuffers.add(backingStore);
 }
 
@@ -513,7 +512,6 @@ void LayerTreeRenderer::updateTile(WebLayerID layerID, int tileID, const TileUpd
     RefPtr<CoordinatedBackingStore> backingStore = getBackingStore(layer);
     ASSERT(backingStore);
     backingStore->updateTile(tileID, update.sourceRect, update.tileRect, update.surface, update.offset);
-    resetBackingStoreSizeToLayerSize(layer);
     m_backingStoresWithPendingBuffers.add(backingStore);
 }