1 files changed, 27 insertions, 16 deletions

diff --git a/WebCore/rendering/RenderLayer.cpp b/WebCore/rendering/RenderLayer.cpp
index 2d2559c..27ff32f 100644
--- a/WebCore/rendering/RenderLayer.cpp
+++ b/WebCore/rendering/RenderLayer.cpp
@@ -143,8 +143,8 @@ RenderLayer::RenderLayer(RenderBoxModelObject* renderer)
     , m_height(0)
     , m_scrollX(0)
     , m_scrollY(0)
-    , m_scrollOriginX(0)
     , m_scrollLeftOverflow(0)
+    , m_scrollTopOverflow(0)
     , m_scrollWidth(0)
     , m_scrollHeight(0)
     , m_inResizeMode(false)
@@ -249,6 +249,15 @@ bool RenderLayer::hasAcceleratedCompositing() const
 #endif
 }
 
+bool RenderLayer::canRender3DTransforms() const
+{
+#if USE(ACCELERATED_COMPOSITING)
+    return compositor()->canRender3DTransforms();
+#else
+    return false;
+#endif
+}
+
 void RenderLayer::updateLayerPositions(UpdateLayerPositionsFlags flags, IntPoint* cachedOffset)
 {
     if (flags & DoFullRepaint) {
@@ -310,8 +319,6 @@ void RenderLayer::updateLayerPositions(UpdateLayerPositionsFlags flags, IntPoint
 
     updateVisibilityStatus();
 
-    updateTransform();
-
     if (flags & UpdatePagination)
         updatePagination();
     else
@@ -429,7 +436,7 @@ void RenderLayer::updateTransform()
         ASSERT(box);
         m_transform->makeIdentity();
         box->style()->applyTransform(*m_transform, box->borderBoxRect().size(), RenderStyle::IncludeTransformOrigin);
-        makeMatrixRenderable(*m_transform, hasAcceleratedCompositing());
+        makeMatrixRenderable(*m_transform, canRender3DTransforms());
     }
 
     if (had3DTransform != has3DTransform())
@@ -446,7 +453,7 @@ TransformationMatrix RenderLayer::currentTransform() const
         TransformationMatrix currTransform;
         RefPtr<RenderStyle> style = renderer()->animation()->getAnimatedStyleForRenderer(renderer());
         style->applyTransform(currTransform, renderBox()->borderBoxRect().size(), RenderStyle::IncludeTransformOrigin);
-        makeMatrixRenderable(currTransform, hasAcceleratedCompositing());
+        makeMatrixRenderable(currTransform, canRender3DTransforms());
         return currTransform;
     }
 #endif
@@ -1341,11 +1348,12 @@ void RenderLayer::scrollToOffset(int x, int y, bool updateScrollbars, bool repai
     // complicated (since it will involve testing whether our layer
     // is either occluded by another layer or clipped by an enclosing
     // layer or contains fixed backgrounds, etc.).
-    int newScrollX = x - m_scrollOriginX;
-    if (m_scrollY == y && m_scrollX == newScrollX)
+    int newScrollX = x - m_scrollOrigin.x();
+    int newScrollY = y - m_scrollOrigin.y();
+    if (m_scrollY == newScrollY && m_scrollX == newScrollX)
         return;
     m_scrollX = newScrollX;
-    m_scrollY = y;
+    m_scrollY = newScrollY;
 
     // Update the positions of our child layers. Don't have updateLayerPositions() update
     // compositing layers, because we need to do a deep update from the compositing ancestor.
@@ -1999,22 +2007,26 @@ void RenderLayer::computeScrollDimensions(bool* needHBar, bool* needVBar)
     
     m_scrollDimensionsDirty = false;
     
-    bool ltr = renderer()->style()->isLeftToRightDirection();
-
     int clientWidth = box->clientWidth();
     int clientHeight = box->clientHeight();
 
-    m_scrollLeftOverflow = ltr ? 0 : min(0, box->leftmostPosition(true, false) - box->borderLeft());
+    bool hasLeftOverflow = (!box->style()->isHorizontalWritingMode() || !box->style()->isLeftToRightDirection()) && box->style()->writingMode() != LeftToRightWritingMode;
+    bool hasTopOverflow = (box->style()->isHorizontalWritingMode() || !box->style()->isLeftToRightDirection()) && box->style()->writingMode() != TopToBottomWritingMode;
+
+    m_scrollLeftOverflow = !hasLeftOverflow ? 0 : min(0, box->leftmostPosition(true, false) - box->borderLeft());
+    m_scrollTopOverflow = !hasTopOverflow ? 0 : min(0, box->topmostPosition(true, false) - box->borderTop());
 
-    int rightPos = ltr ?
+    int rightPos = !hasLeftOverflow ?
                     box->rightmostPosition(true, false) - box->borderLeft() :
                     clientWidth - m_scrollLeftOverflow;
-    int bottomPos = box->lowestPosition(true, false) - box->borderTop();
+    int bottomPos = !hasTopOverflow ?
+                    box->lowestPosition(true, false) - box->borderTop() :
+                    clientHeight - m_scrollTopOverflow;
 
     m_scrollWidth = max(rightPos, clientWidth);
     m_scrollHeight = max(bottomPos, clientHeight);
     
-    m_scrollOriginX = ltr ? 0 : m_scrollWidth - clientWidth;
+    m_scrollOrigin = IntPoint(!hasLeftOverflow ? 0 : m_scrollWidth - clientWidth, !hasTopOverflow ? 0 : m_scrollHeight - clientHeight);
 
     if (needHBar)
         *needHBar = rightPos > clientWidth;
@@ -2028,7 +2040,6 @@ void RenderLayer::updateOverflowStatus(bool horizontalOverflow, bool verticalOve
         m_horizontalOverflow = horizontalOverflow;
         m_verticalOverflow = verticalOverflow;
         m_overflowStatusDirty = false;
-        
         return;
     }
     
@@ -2399,7 +2410,7 @@ void RenderLayer::paintLayer(RenderLayer* rootLayer, GraphicsContext* p,
     // Avoid painting layers when stylesheets haven't loaded.  This eliminates FOUC.
     // It's ok not to draw, because later on, when all the stylesheets do load, updateStyleSelector on the Document
     // will do a full repaint().
-    if (renderer()->document()->didLayoutWithPendingStylesheets() && !renderer()->isRenderView() && !renderer()->isRoot())
+    if (renderer()->document()->mayCauseFlashOfUnstyledContent() && !renderer()->isRenderView() && !renderer()->isRoot())
         return;
     
     // If this layer is totally invisible then there is nothing to paint.