Fix classic scrollbars getting occluded with containerless scrolling. (bug 1100756, r=roc)

--HG--
extra : rebase_source : fcf95ab0c435d9c29a6a3552fe05d7f1ad3bc0ec

gfx/layers/Layers.cpp

@@ -208,6 +208,7 @@ Layer::Layer(LayerManager* aManager, void* aImplData) :
   mStickyPositionData(nullptr),
   mScrollbarTargetId(FrameMetrics::NULL_SCROLL_ID),
   mScrollbarDirection(ScrollDirection::NONE),
+  mIsScrollbarContainer(false),
   mDebugColorIndex(0),
   mAnimationGeneration(0)
 {}

gfx/layers/Layers.h

@@ -1204,6 +1204,15 @@ public:
     }
   }
 
+  // Set during construction for the container layer of scrollbar components.
+  void SetIsScrollbarContainer()
+  {
+    if (!mIsScrollbarContainer) {
+      mIsScrollbarContainer = true;
+      Mutated();
+    }
+  }
+
   // These getters can be used anytime.
   float GetOpacity() { return mOpacity; }
   gfx::CompositionOp GetMixBlendMode() const { return mMixBlendMode; }
@@ -1238,6 +1247,7 @@ public:
   const LayerRect& GetStickyScrollRangeInner() { return mStickyPositionData->mInner; }
   FrameMetrics::ViewID GetScrollbarTargetContainerId() { return mScrollbarTargetId; }
   ScrollDirection GetScrollbarDirection() { return mScrollbarDirection; }
+  bool IsScrollbarContainer() { return mIsScrollbarContainer; }
   Layer* GetMaskLayer() const { return mMaskLayer; }
 
 
@@ -1676,6 +1686,7 @@ protected:
   nsAutoPtr<StickyPositionData> mStickyPositionData;
   FrameMetrics::ViewID mScrollbarTargetId;
   ScrollDirection mScrollbarDirection;
+  bool mIsScrollbarContainer;
   DebugOnly<uint32_t> mDebugColorIndex;
   // If this layer is used for OMTA, then this counter is used to ensure we
   // stay in sync with the animation manager

layout/base/FrameLayerBuilder.cpp

@@ -3634,7 +3634,7 @@ ContainerState::PostprocessRetainedLayers(nsIntRegion* aOpaqueRegionForContainer
 
     if (hideAll) {
       e->mVisibleRegion.SetEmpty();
-    } else {
+    } else if (!e->mLayer->IsScrollbarContainer()) {
       const nsIntRect* clipRect = e->mLayer->GetClipRect();
       if (clipRect && opaqueRegionForContainer >= 0 &&
           opaqueRegions[opaqueRegionForContainer].mOpaqueRegion.Contains(*clipRect)) {

layout/base/nsDisplayList.cpp

@@ -3982,6 +3982,9 @@ nsDisplayOwnLayer::BuildLayer(nsDisplayListBuilder* aBuilder,
   if (mFlags & HORIZONTAL_SCROLLBAR) {
     layer->SetScrollbarData(mScrollTarget, Layer::ScrollDirection::HORIZONTAL);
   }
+  if (mFlags & SCROLLBAR_CONTAINER) {
+    layer->SetIsScrollbarContainer();
+  }
 
   if (mFlags & GENERATE_SUBDOC_INVALIDATIONS) {
     mFrame->PresContext()->SetNotifySubDocInvalidationData(layer);

layout/base/nsDisplayList.h

@@ -2955,7 +2955,8 @@ public:
     GENERATE_SUBDOC_INVALIDATIONS = 0x01,
     VERTICAL_SCROLLBAR = 0x02,
     HORIZONTAL_SCROLLBAR = 0x04,
-    GENERATE_SCROLLABLE_LAYER = 0x08
+    GENERATE_SCROLLABLE_LAYER = 0x08,
+    SCROLLBAR_CONTAINER = 0x10
   };
 
   /**

layout/generic/nsGfxScrollFrame.cpp

@@ -2534,19 +2534,28 @@ MaxZIndexInListOfItemsContainedInFrame(nsDisplayList* aList, nsIFrame* aFrame)
   return maxZIndex;
 }
 
+static const uint32_t APPEND_OWN_LAYER = 0x1;
+static const uint32_t APPEND_POSITIONED = 0x2;
+static const uint32_t APPEND_SCROLLBAR_CONTAINER = 0x4;
+
 static void
 AppendToTop(nsDisplayListBuilder* aBuilder, const nsDisplayListSet& aLists,
-            nsDisplayList* aSource, nsIFrame* aSourceFrame, bool aOwnLayer,
-            bool aPositioned)
+            nsDisplayList* aSource, nsIFrame* aSourceFrame, uint32_t aFlags)
 {
   if (aSource->IsEmpty())
     return;
 
-  nsDisplayWrapList* newItem = aOwnLayer?
-    new (aBuilder) nsDisplayOwnLayer(aBuilder, aSourceFrame, aSource) :
-    new (aBuilder) nsDisplayWrapList(aBuilder, aSourceFrame, aSource);
+  nsDisplayWrapList* newItem;
+  if (aFlags & APPEND_OWN_LAYER) {
+    uint32_t flags = (aFlags & APPEND_SCROLLBAR_CONTAINER)
+                     ? nsDisplayOwnLayer::SCROLLBAR_CONTAINER
+                     : 0;
+    newItem = new (aBuilder) nsDisplayOwnLayer(aBuilder, aSourceFrame, aSource, flags);
+  } else {
+    newItem = new (aBuilder) nsDisplayWrapList(aBuilder, aSourceFrame, aSource);
+  }
 
-  if (aPositioned) {
+  if (aFlags & APPEND_POSITIONED) {
     // We want overlay scrollbars to always be on top of the scrolled content,
     // but we don't want them to unnecessarily cover overlapping elements from
     // outside our scroll frame.
@@ -2629,11 +2638,14 @@ ScrollFrameHelper::AppendScrollPartsTo(nsDisplayListBuilder*   aBuilder,
 
   for (uint32_t i = 0; i < scrollParts.Length(); ++i) {
     uint32_t flags = 0;
+    uint32_t appendToTopFlags = 0;
     if (scrollParts[i] == mVScrollbarBox) {
       flags |= nsDisplayOwnLayer::VERTICAL_SCROLLBAR;
+      appendToTopFlags |= APPEND_SCROLLBAR_CONTAINER;
     }
     if (scrollParts[i] == mHScrollbarBox) {
       flags |= nsDisplayOwnLayer::HORIZONTAL_SCROLLBAR;
+      appendToTopFlags |= APPEND_SCROLLBAR_CONTAINER;
     }
 
     // The display port doesn't necessarily include the scrollbars, so just
@@ -2653,13 +2665,18 @@ ScrollFrameHelper::AppendScrollPartsTo(nsDisplayListBuilder*   aBuilder,
     // Always create layers for overlay scrollbars so that we don't create a
     // giant layer covering the whole scrollport if both scrollbars are visible.
     bool isOverlayScrollbar = (flags != 0) && overlayScrollbars;
-    bool createLayer = aCreateLayer || isOverlayScrollbar;
+    if (aCreateLayer || isOverlayScrollbar) {
+      appendToTopFlags |= APPEND_OWN_LAYER;
+    }
+    if (aPositioned) {
+      appendToTopFlags |= APPEND_POSITIONED;
+    }
 
     // DISPLAY_CHILD_FORCE_STACKING_CONTEXT put everything into
     // partList.PositionedDescendants().
     ::AppendToTop(aBuilder, aLists,
                   partList.PositionedDescendants(), scrollParts[i],
-                  createLayer, aPositioned);
+                  appendToTopFlags);
   }
 }
 
@@ -3143,9 +3160,11 @@ ScrollFrameHelper::ComputeFrameMetrics(Layer* aLayer,
                                        nsRect* aClipRect,
                                        nsTArray<FrameMetrics>* aOutput) const
 {
-  nsRect scrollport = mScrollPort +
-    mOuter->GetOffsetToCrossDoc(aContainerReferenceFrame);
-  if (mAddClipRectToLayer) {
+  nsPoint toReferenceFrame = mOuter->GetOffsetToCrossDoc(aContainerReferenceFrame);
+  nsRect scrollport = mScrollPort + toReferenceFrame;
+  if (!gfxPrefs::LayoutUseContainersForRootFrames() || mAddClipRectToLayer) {
+    // When using containers, the container layer contains the clip. Otherwise
+    // we always include the clip.
     *aClipRect = scrollport;
   }