Bug 691106 - Merge sequential nsDisplayTransforms and give them unique frame keys. r=roc

layout/base/nsDisplayList.cpp

@@ -2451,13 +2451,6 @@ nsDisplayTransform::GetResultingTransformMatrix(const nsIFrame* aFrame,
       *aOutAncestor = nsLayoutUtils::GetCrossDocParentFrame(aFrame);
   }
 
-  /* Preserve-3d can cause frames without a transform to get an nsDisplayTransform created, we should
-   * use our parent's transform here.
-   */
-  if (!aFrame->GetStyleDisplay()->HasTransform()) {
-    return GetResultingTransformMatrix(aFrame->GetParent(), aOrigin - aFrame->GetPosition(), aFactor, nsnull, aOutAncestor);
-  }
-
   /* Account for the -moz-transform-origin property by translating the
    * coordinate space to the new origin.
    */

layout/base/nsDisplayList.h

@@ -2079,16 +2079,16 @@ public:
    * ferries the underlying frame to the nsDisplayItem constructor.
    */
   nsDisplayTransform(nsDisplayListBuilder* aBuilder, nsIFrame *aFrame,
-                     nsDisplayList *aList) :
-    nsDisplayItem(aBuilder, aFrame), mStoredList(aBuilder, aFrame, aList)
+                     nsDisplayList *aList, PRUint32 aIndex = 0) :
+    nsDisplayItem(aBuilder, aFrame), mStoredList(aBuilder, aFrame, aList), mIndex(aIndex)
   {
     MOZ_COUNT_CTOR(nsDisplayTransform);
     NS_ABORT_IF_FALSE(aFrame, "Must have a frame!");
   }
 
   nsDisplayTransform(nsDisplayListBuilder* aBuilder, nsIFrame *aFrame,
-                     nsDisplayItem *aItem) :
-  nsDisplayItem(aBuilder, aFrame), mStoredList(aBuilder, aFrame, aItem)
+                     nsDisplayItem *aItem, PRUint32 aIndex = 0) :
+  nsDisplayItem(aBuilder, aFrame), mStoredList(aBuilder, aFrame, aItem), mIndex(aIndex)
   {
     MOZ_COUNT_CTOR(nsDisplayTransform);
     NS_ABORT_IF_FALSE(aFrame, "Must have a frame!");
@@ -2127,6 +2127,12 @@ public:
                                    nsRegion *aVisibleRegion,
                                    const nsRect& aAllowVisibleRegionExpansion);
   virtual bool TryMerge(nsDisplayListBuilder *aBuilder, nsDisplayItem *aItem);
+  
+  virtual PRUint32 GetPerFrameKey() { return (mIndex << nsDisplayItem::TYPE_BITS) | nsDisplayItem::GetPerFrameKey(); }
+
+  enum {
+    INDEX_MAX = PR_UINT32_MAX >> nsDisplayItem::TYPE_BITS
+  };
 
   const gfx3DMatrix& GetTransform(float aFactor);
 
@@ -2205,6 +2211,7 @@ private:
   nsDisplayWrapList mStoredList;
   gfx3DMatrix mTransform;
   float mCachedFactor;
+  PRUint32 mIndex;
 };
 
 /**

layout/generic/nsFrame.cpp

@@ -1518,47 +1518,78 @@ DisplayDebugBorders(nsDisplayListBuilder* aBuilder, nsIFrame* aFrame,
 #endif
 
 static nsresult
-WrapPreserve3DList(nsIFrame *aFrame, nsDisplayListBuilder *aBuilder, nsDisplayList *aList)
+WrapPreserve3DListInternal(nsIFrame* aFrame, nsDisplayListBuilder *aBuilder, nsDisplayList *aList, PRUint32& aIndex)
 {
+  if (aIndex > nsDisplayTransform::INDEX_MAX) {
+    return NS_OK;
+  }
+
   nsresult rv = NS_OK;
   nsDisplayList newList;
+  nsDisplayList temp;
   while (nsDisplayItem *item = aList->RemoveBottom()) {
     nsIFrame *childFrame = item->GetUnderlyingFrame();
     NS_ASSERTION(childFrame, "All display items to be wrapped must have a frame!");
+
+    // We accumulate sequential items that aren't transforms into the 'temp' list
+    // and then flush this list into newList by wrapping the whole lot with a single
+    // nsDisplayTransform.
+
     if (childFrame->GetParent()->Preserves3DChildren()) {
       switch (item->GetType()) {
         case nsDisplayItem::TYPE_TRANSFORM: {
+          if (!temp.IsEmpty()) {
+            newList.AppendToTop(new (aBuilder) nsDisplayTransform(aBuilder, aFrame, &temp, aIndex++));
+          }
+          newList.AppendToTop(item);
           break;
         }
         case nsDisplayItem::TYPE_WRAP_LIST: {
+          if (!temp.IsEmpty()) {
+            newList.AppendToTop(new (aBuilder) nsDisplayTransform(aBuilder, aFrame, &temp, aIndex++));
+          }
           nsDisplayWrapList *list = static_cast<nsDisplayWrapList*>(item);
-          rv = WrapPreserve3DList(aFrame, aBuilder, list->GetList());
+          rv = WrapPreserve3DListInternal(aFrame, aBuilder, list->GetList(), aIndex);
+          newList.AppendToTop(item);
           break;
         }
         case nsDisplayItem::TYPE_OPACITY: {
+          if (!temp.IsEmpty()) {
+            newList.AppendToTop(new (aBuilder) nsDisplayTransform(aBuilder, aFrame, &temp, aIndex++));
+          }
           nsDisplayOpacity *opacity = static_cast<nsDisplayOpacity*>(item);
-          rv = WrapPreserve3DList(aFrame, aBuilder, opacity->GetList());
+          rv = WrapPreserve3DListInternal(aFrame, aBuilder, opacity->GetList(), aIndex);
+          newList.AppendToTop(item);
           break;
         }
         default: {
-          item = new (aBuilder) nsDisplayTransform(aBuilder, childFrame, item);
+          temp.AppendToTop(item);
           break;
         }
       } 
     } else {
-      item = new (aBuilder) nsDisplayTransform(aBuilder, childFrame, item);
+      temp.AppendToTop(item);
     }
  
-    if (NS_FAILED(rv) || !item)
+    if (NS_FAILED(rv) || !item || aIndex > nsDisplayTransform::INDEX_MAX)
       return rv;
-
-    newList.AppendToTop(item);
+  }
+    
+  if (!temp.IsEmpty()) {
+    newList.AppendToTop(new (aBuilder) nsDisplayTransform(aBuilder, aFrame, &temp, aIndex++));
   }
 
   aList->AppendToTop(&newList);
   return NS_OK;
 }
 
+static nsresult
+WrapPreserve3DList(nsIFrame* aFrame, nsDisplayListBuilder* aBuilder, nsDisplayList *aList)
+{
+  PRUint32 index = 0;
+  return WrapPreserve3DListInternal(aFrame, aBuilder, aList, index);
+}
+
 nsresult
 nsIFrame::BuildDisplayListForStackingContext(nsDisplayListBuilder* aBuilder,
                                              const nsRect&         aDirtyRect,