Backed out changeset e95971991caa (bug 1022612)

layout/base/FrameLayerBuilder.cpp

@@ -2078,10 +2078,15 @@ ContainerState::PopThebesLayerData()
 
 static bool
 SuppressComponentAlpha(nsDisplayListBuilder* aBuilder,
-                       nsDisplayItem* aItem)
+                       nsDisplayItem* aItem,
+                       const nsRect& aComponentAlphaBounds)
 {
-  // Suppress component alpha for items in the toplevel window chrome that
-  // aren't transformed.
+  const nsRegion* windowTransparentRegion = aBuilder->GetFinalTransparentRegion();
+  if (!windowTransparentRegion || windowTransparentRegion->IsEmpty())
+    return false;
+
+  // Suppress component alpha for items in the toplevel window that are over
+  // the window translucent area
   nsIFrame* f = aItem->Frame();
   nsIFrame* ref = aBuilder->RootReferenceFrame();
   if (f->PresContext() != ref->PresContext())
@@ -2091,7 +2096,15 @@ SuppressComponentAlpha(nsDisplayListBuilder* aBuilder,
     if (t->IsTransformed())
       return false;
   }
-  return true;
+
+  return windowTransparentRegion->Intersects(aComponentAlphaBounds);
+}
+
+static bool
+WindowHasTransparency(nsDisplayListBuilder* aBuilder)
+{
+  const nsRegion* windowTransparentRegion = aBuilder->GetFinalTransparentRegion();
+  return windowTransparentRegion && !windowTransparentRegion->IsEmpty();
 }
 
 void
@@ -2191,7 +2204,9 @@ ThebesLayerData::Accumulate(ContainerState* aState,
        // Opaque display items in chrome documents whose window is partially
        // transparent are always added to the opaque region. This helps ensure
        // that we get as much subpixel-AA as possible in the chrome.
-       if (tmp.GetNumRects() <= 4 || aItem->Frame()->PresContext()->IsChrome()) {
+       if (tmp.GetNumRects() <= 4 ||
+           (WindowHasTransparency(aState->mBuilder) &&
+            aItem->Frame()->PresContext()->IsChrome())) {
         mOpaqueRegion = tmp;
       }
     }
@@ -2203,7 +2218,7 @@ ThebesLayerData::Accumulate(ContainerState* aState,
       nsIntRect componentAlphaRect =
         aState->ScaleToOutsidePixels(componentAlpha, false).Intersect(aVisibleRect);
       if (!mOpaqueRegion.Contains(componentAlphaRect)) {
-        if (SuppressComponentAlpha(aState->mBuilder, aItem)) {
+        if (SuppressComponentAlpha(aState->mBuilder, aItem, componentAlpha)) {
           aItem->DisableComponentAlpha();
         } else {
           mNeedComponentAlpha = true;

layout/base/nsDisplayList.cpp

@@ -494,6 +494,7 @@ nsDisplayListBuilder::nsDisplayListBuilder(nsIFrame* aReferenceFrame,
       mIgnoreScrollFrame(nullptr),
       mLayerEventRegions(nullptr),
       mCurrentTableItem(nullptr),
+      mFinalTransparentRegion(nullptr),
       mCurrentFrame(aReferenceFrame),
       mCurrentReferenceFrame(aReferenceFrame),
       mDirtyRect(-1,-1,-1,-1),

layout/base/nsDisplayList.h

@@ -460,6 +460,19 @@ public:
    */
   void MarkPreserve3DFramesForDisplayList(nsIFrame* aDirtyFrame, const nsRect& aDirtyRect);
 
+  /**
+   * Get the area of the final transparent region.
+   */
+  const nsRegion* GetFinalTransparentRegion() { return mFinalTransparentRegion; }
+  /**
+   * Record the area of the final transparent region after all visibility
+   * calculations were performed.
+   */
+  void SetFinalTransparentRegion(const nsRegion& aFinalTransparentRegion)
+  {
+    mFinalTransparentRegion = &aFinalTransparentRegion;
+  }
+
   const nsTArray<ThemeGeometry>& GetThemeGeometries() { return mThemeGeometries; }
 
   /**
@@ -759,6 +772,7 @@ private:
   nsAutoTArray<ThemeGeometry,2>  mThemeGeometries;
   nsDisplayTableItem*            mCurrentTableItem;
   DisplayListClipState           mClipState;
+  const nsRegion*                mFinalTransparentRegion;
   // mCurrentFrame is the frame that we're currently calling (or about to call)
   // BuildDisplayList on.
   const nsIFrame*                mCurrentFrame;

layout/base/nsLayoutUtils.cpp

@@ -2957,6 +2957,7 @@ nsLayoutUtils::PaintFrame(nsRenderingContext* aRenderingContext, nsIFrame* aFram
     } else if (!(aFlags & PAINT_DOCUMENT_RELATIVE)) {
       nsIWidget *widget = aFrame->GetNearestWidget();
       if (widget) {
+        builder.SetFinalTransparentRegion(visibleRegion);
         // If we're finished building display list items for painting of the outermost
         // pres shell, notify the widget about any toolbars we've encountered.
         widget->UpdateThemeGeometries(builder.GetThemeGeometries());