Bug 1056340 - Clip viewport fixed position overflow to scroll frame. r=roc

gfx/2d/DrawTargetCairo.cpp

@@ -167,6 +167,7 @@ CopyToImageSurface(unsigned char *aData,
                           aRect.y * aStride +
                           aRect.x * pixelWidth;
 
+  MOZ_ASSERT(aStride >= aRect.width * pixelWidth);
   for (int32_t y = 0; y < aRect.height; ++y) {
     memcpy(surfData + y * surfStride,
            source + y * aStride,

layout/generic/nsGfxScrollFrame.h

@@ -736,6 +736,9 @@ public:
     mHelper.ComputeFrameMetrics(aLayer, aContainerReferenceFrame,
                                 aParameters, aClipRect, aOutput);
   }
+  virtual bool IsIgnoringViewportClipping() const MOZ_OVERRIDE {
+    return mHelper.IsIgnoringViewportClipping();
+  }
 
   // nsIStatefulFrame
   NS_IMETHOD SaveState(nsPresState** aState) MOZ_OVERRIDE {
@@ -1088,6 +1091,9 @@ public:
     mHelper.ComputeFrameMetrics(aLayer, aContainerReferenceFrame,
                                 aParameters, aClipRect, aOutput);
   }
+  virtual bool IsIgnoringViewportClipping() const MOZ_OVERRIDE {
+    return mHelper.IsIgnoringViewportClipping();
+  }
 
   // nsIStatefulFrame
   NS_IMETHOD SaveState(nsPresState** aState) MOZ_OVERRIDE {

layout/generic/nsIScrollableFrame.h

@@ -380,6 +380,11 @@ public:
                                    const ContainerLayerParameters& aParameters,
                                    nsRect* aOutClipRect,
                                    nsTArray<FrameMetrics>* aOutput) const = 0;
+
+  /**
+   * If this scroll frame is ignoring viewporting clipping
+   */
+  virtual bool IsIgnoringViewportClipping() const = 0;
 };
 
 #endif

layout/generic/nsViewportFrame.cpp

@@ -190,7 +190,7 @@ ViewportFrame::Reflow(nsPresContext*           aPresContext,
   // being already set.  Note that the computed height may be
   // unconstrained; that's ok.  Consumers should watch out for that.
   SetSize(nsSize(aReflowState.ComputedWidth(), aReflowState.ComputedHeight()));
- 
+
   // Reflow the main content first so that the placeholders of the
   // fixed-position frames will be in the right places on an initial
   // reflow.
@@ -236,10 +236,6 @@ ViewportFrame::Reflow(nsPresContext*           aPresContext,
   aDesiredSize.SetSize(wm, maxSize);
   aDesiredSize.SetOverflowAreasToDesiredBounds();
 
-  if (mFrames.NotEmpty()) {
-    ConsiderChildOverflow(aDesiredSize.mOverflowAreas, mFrames.FirstChild());
-  }
-
   if (IsAbsoluteContainer()) {
     // Make a copy of the reflow state and change the computed width and height
     // to reflect the available space for the fixed items
@@ -262,6 +258,16 @@ ViewportFrame::Reflow(nsPresContext*           aPresContext,
                                          rect,
                                          false, true, true, // XXX could be optimized
                                          &aDesiredSize.mOverflowAreas);
+
+    nsIScrollableFrame* rootScrollFrame =
+                    aPresContext->PresShell()->GetRootScrollFrameAsScrollable();
+    if (rootScrollFrame && !rootScrollFrame->IsIgnoringViewportClipping()) {
+      aDesiredSize.SetOverflowAreasToDesiredBounds();
+    }
+  }
+
+  if (mFrames.NotEmpty()) {
+    ConsiderChildOverflow(aDesiredSize.mOverflowAreas, mFrames.FirstChild());
   }
 
   // If we were dirty then do a repaint
@@ -287,6 +293,18 @@ ViewportFrame::Reflow(nsPresContext*           aPresContext,
   NS_FRAME_SET_TRUNCATION(aStatus, aReflowState, aDesiredSize);
 }
 
+bool
+ViewportFrame::UpdateOverflow()
+{
+  nsIScrollableFrame* rootScrollFrame =
+    PresContext()->PresShell()->GetRootScrollFrameAsScrollable();
+  if (rootScrollFrame && !rootScrollFrame->IsIgnoringViewportClipping()) {
+    return false;
+  }
+
+  return nsFrame::UpdateOverflow();
+}
+
 nsIAtom*
 ViewportFrame::GetType() const
 {

layout/generic/nsViewportFrame.h

@@ -17,8 +17,8 @@
 class nsPresContext;
 
 /**
-  * ViewportFrame is the parent of a single child - the doc root frame or a scroll frame 
-  * containing the doc root frame. ViewportFrame stores this child in its primary child 
+  * ViewportFrame is the parent of a single child - the doc root frame or a scroll frame
+  * containing the doc root frame. ViewportFrame stores this child in its primary child
   * list.
   */
 class ViewportFrame : public nsContainerFrame {
@@ -68,6 +68,8 @@ public:
    */
   virtual nsIAtom* GetType() const MOZ_OVERRIDE;
 
+  virtual bool UpdateOverflow() MOZ_OVERRIDE;
+
   /**
    * Adjust aReflowState to account for scrollbars and pres shell
    * GetScrollPositionClampingScrollPortSizeSet and