Bug 1013392 - Put APZ scrollbar annotations on the scrollbar thumb. r=roc

layout/base/nsDisplayList.h

@@ -118,6 +118,7 @@ public:
   typedef mozilla::DisplayListClipState DisplayListClipState;
   typedef nsIWidget::ThemeGeometry ThemeGeometry;
   typedef mozilla::layers::Layer Layer;
+  typedef mozilla::layers::FrameMetrics FrameMetrics;
   typedef mozilla::layers::FrameMetrics::ViewID ViewID;
 
   /**
@@ -257,6 +258,15 @@ public:
    * Get the ViewID of the nearest scrolling ancestor frame.
    */
   ViewID GetCurrentScrollParentId() const { return mCurrentScrollParentId; }
+  /**
+   * Get the ViewID and the scrollbar flags corresponding to the scrollbar for
+   * which we are building display items at the moment.
+   */
+  void GetScrollbarInfo(ViewID* aOutScrollbarTarget, uint32_t* aOutScrollbarFlags)
+  {
+    *aOutScrollbarTarget = mCurrentScrollbarTarget;
+    *aOutScrollbarFlags = mCurrentScrollbarFlags;
+  }
   /**
    * Calling this setter makes us include all out-of-flow descendant
    * frames in the display list, wherever they may be positioned (even
@@ -630,6 +640,29 @@ public:
     ViewID                mOldValue;
   };
 
+  /**
+   * A helper class to temporarily set the value of mCurrentScrollbarTarget
+   * and mCurrentScrollbarFlags.
+   */
+  class AutoCurrentScrollbarInfoSetter;
+  friend class AutoCurrentScrollbarInfoSetter;
+  class AutoCurrentScrollbarInfoSetter {
+  public:
+    AutoCurrentScrollbarInfoSetter(nsDisplayListBuilder* aBuilder, ViewID aScrollTargetID,
+                                   uint32_t aScrollbarFlags)
+     : mBuilder(aBuilder) {
+      aBuilder->mCurrentScrollbarTarget = aScrollTargetID;
+      aBuilder->mCurrentScrollbarFlags = aScrollbarFlags;
+    }
+    ~AutoCurrentScrollbarInfoSetter() {
+      // No need to restore old values because scrollbars cannot be nested.
+      mBuilder->mCurrentScrollbarTarget = FrameMetrics::NULL_SCROLL_ID;
+      mBuilder->mCurrentScrollbarFlags = 0;
+    }
+  private:
+    nsDisplayListBuilder* mBuilder;
+  };
+
   // Helpers for tables
   nsDisplayTableItem* GetCurrentTableItem() { return mCurrentTableItem; }
   void SetCurrentTableItem(nsDisplayTableItem* aTableItem) { mCurrentTableItem = aTableItem; }
@@ -741,6 +774,8 @@ private:
   nsTArray<DisplayItemClip*>     mDisplayItemClipsToDestroy;
   Mode                           mMode;
   ViewID                         mCurrentScrollParentId;
+  ViewID                         mCurrentScrollbarTarget;
+  uint32_t                       mCurrentScrollbarFlags;
   BlendModeSet                   mContainedBlendModes;
   bool                           mBuildCaret;
   bool                           mIgnoreSuppression;

layout/generic/nsGfxScrollFrame.cpp

@@ -2134,15 +2134,13 @@ MaxZIndexInList(nsDisplayList* aList, nsDisplayListBuilder* aBuilder)
 static void
 AppendToTop(nsDisplayListBuilder* aBuilder, const nsDisplayListSet& aLists,
             nsDisplayList* aSource, nsIFrame* aSourceFrame, bool aOwnLayer,
-            uint32_t aFlags, mozilla::layers::FrameMetrics::ViewID aScrollTargetId,
             bool aPositioned)
 {
   if (aSource->IsEmpty())
     return;
 
   nsDisplayWrapList* newItem = aOwnLayer?
-    new (aBuilder) nsDisplayOwnLayer(aBuilder, aSourceFrame, aSource,
-                                     aFlags, aScrollTargetId) :
+    new (aBuilder) nsDisplayOwnLayer(aBuilder, aSourceFrame, aSource) :
     new (aBuilder) nsDisplayWrapList(aBuilder, aSourceFrame, aSource);
 
   if (aPositioned) {
@@ -2211,11 +2209,6 @@ ScrollFrameHelper::AppendScrollPartsTo(nsDisplayListBuilder*   aBuilder,
   scrollParts.Sort(HoveredStateComparator());
 
   for (uint32_t i = 0; i < scrollParts.Length(); ++i) {
-    nsDisplayListCollection partList;
-    mOuter->BuildDisplayListForChild(
-      aBuilder, scrollParts[i], aDirtyRect, partList,
-      nsIFrame::DISPLAY_CHILD_FORCE_STACKING_CONTEXT);
-
     uint32_t flags = 0;
     if (scrollParts[i] == mVScrollbarBox) {
       flags |= nsDisplayOwnLayer::VERTICAL_SCROLLBAR;
@@ -2224,11 +2217,18 @@ ScrollFrameHelper::AppendScrollPartsTo(nsDisplayListBuilder*   aBuilder,
       flags |= nsDisplayOwnLayer::HORIZONTAL_SCROLLBAR;
     }
 
+    nsDisplayListBuilder::AutoCurrentScrollbarInfoSetter
+      infoSetter(aBuilder, scrollTargetId, flags);
+    nsDisplayListCollection partList;
+    mOuter->BuildDisplayListForChild(
+      aBuilder, scrollParts[i], aDirtyRect, partList,
+      nsIFrame::DISPLAY_CHILD_FORCE_STACKING_CONTEXT);
+ 
     // DISPLAY_CHILD_FORCE_STACKING_CONTEXT put everything into
     // partList.PositionedDescendants().
     ::AppendToTop(aBuilder, aLists,
                   partList.PositionedDescendants(), scrollParts[i],
-                  aCreateLayer, flags, scrollTargetId, aPositioned);
+                  aCreateLayer, aPositioned);
   }
 }
 

layout/xul/nsBoxFrame.cpp

@@ -1308,14 +1308,24 @@ nsBoxFrame::BuildDisplayList(nsDisplayListBuilder*   aBuilder,
                              const nsRect&           aDirtyRect,
                              const nsDisplayListSet& aLists)
 {
-  // forcelayer is only supported on XUL elements with box layout
-  bool forceLayer =
-    GetContent()->HasAttr(kNameSpaceID_None, nsGkAtoms::layer) &&
-    GetContent()->IsXUL();
+  bool forceLayer = false;
+  uint32_t flags = 0;
+  mozilla::layers::FrameMetrics::ViewID scrollTargetId =
+    mozilla::layers::FrameMetrics::NULL_SCROLL_ID;
 
+  if (GetContent()->IsXUL()) {
+    // forcelayer is only supported on XUL elements with box layout
+    if (GetContent()->HasAttr(kNameSpaceID_None, nsGkAtoms::layer)) {
+      forceLayer = true;
+    } else {
+      nsIFrame* parent = GetParentBox(this);
+      if (parent && parent->GetType() == nsGkAtoms::sliderFrame) {
+        forceLayer = true;
+        aBuilder->GetScrollbarInfo(&scrollTargetId, &flags);
+      }
+    }
     // Check for frames that are marked as a part of the region used
     // in calculating glass margins on Windows.
-  if (GetContent()->IsXUL()) {
     const nsStyleDisplay* styles = StyleDisplay();
     if (styles && styles->mAppearance == NS_THEME_WIN_EXCLUDE_GLASS) {
       nsRect rect = nsRect(aBuilder->ToReferenceFrame(this), GetSize());
@@ -1355,9 +1365,10 @@ nsBoxFrame::BuildDisplayList(nsDisplayListBuilder*   aBuilder,
     masterList.AppendToTop(tempLists.Content());
     masterList.AppendToTop(tempLists.PositionedDescendants());
     masterList.AppendToTop(tempLists.Outlines());
+
     // Wrap the list to make it its own layer
     aLists.Content()->AppendNewToTop(new (aBuilder)
-      nsDisplayOwnLayer(aBuilder, this, &masterList));
+      nsDisplayOwnLayer(aBuilder, this, &masterList, flags, scrollTargetId));
   }
 }