Bug 1022612. Part 10: Implement merging and flattening in ProcessDisplayItems. r=mattwoodrow

BuildContainerLayerFor now has to be able to mutate the passed-in display item
list.

--HG--
extra : rebase_source : 6a9727998a5ffb01896a4a2bbdd8d30a24c89dcd

layout/base/FrameLayerBuilder.cpp

@@ -23,6 +23,7 @@
 #include "ImageContainer.h"
 #include "ActiveLayerTracker.h"
 #include "gfx2DGlue.h"
+#include "mozilla/LookAndFeel.h"
 
 #include "GeckoProfiler.h"
 #include "mozilla/gfx/Tools.h"
@@ -521,7 +522,7 @@ public:
    * This is the method that actually walks a display list and builds
    * the child layers.
    */
-  void ProcessDisplayItems(const nsDisplayList& aList, uint32_t aFlags);
+  void ProcessDisplayItems(nsDisplayList* aList, uint32_t aFlags);
   /**
    * This finalizes all the open ThebesLayers by popping every element off
    * mThebesLayerDataStack, then sets the children of the container layer
@@ -2410,6 +2411,31 @@ ContainerState::ChooseAnimatedGeometryRoot(const nsDisplayList& aList,
   return false;
 }
 
+/* Checks if aPotentialScrollItem is a scroll layer item and aPotentialScrollbarItem
+ * is an overlay scrollbar item for the same scroll frame.
+ */
+static bool
+IsScrollLayerItemAndOverlayScrollbarForScrollFrame(
+  nsDisplayItem* aPotentialScrollItem, nsDisplayItem* aPotentialScrollbarItem)
+{
+  if (aPotentialScrollItem->GetType() == nsDisplayItem::TYPE_SCROLL_LAYER &&
+      aPotentialScrollbarItem &&
+      aPotentialScrollbarItem->GetType() == nsDisplayItem::TYPE_OWN_LAYER &&
+      LookAndFeel::GetInt(LookAndFeel::eIntID_UseOverlayScrollbars)) {
+    nsDisplayScrollLayer* scrollItem =
+      static_cast<nsDisplayScrollLayer*>(aPotentialScrollItem);
+    nsDisplayOwnLayer* layerItem =
+      static_cast<nsDisplayOwnLayer*>(aPotentialScrollbarItem);
+    if ((layerItem->GetFlags() &
+         (nsDisplayOwnLayer::VERTICAL_SCROLLBAR |
+          nsDisplayOwnLayer::HORIZONTAL_SCROLLBAR)) &&
+        layerItem->Frame()->GetParent() == scrollItem->GetScrollFrame()) {
+      return true;
+    }
+  }
+  return false;
+}
+
 /*
  * Iterate through the non-clip items in aList and its descendants.
  * For each item we compute the effective clip rect. Each item is assigned
@@ -2425,7 +2451,7 @@ ContainerState::ChooseAnimatedGeometryRoot(const nsDisplayList& aList,
  * of ContainerState::Finish.
  */
 void
-ContainerState::ProcessDisplayItems(const nsDisplayList& aList,
+ContainerState::ProcessDisplayItems(nsDisplayList* aList,
                                     uint32_t aFlags)
 {
   PROFILER_LABEL("ContainerState", "ProcessDisplayItems",
@@ -2438,7 +2464,7 @@ ContainerState::ProcessDisplayItems(const nsDisplayList& aList,
   // layer, so we need to choose which active scrolled root to use for all
   // items.
   if (aFlags & NO_COMPONENT_ALPHA) {
-    if (ChooseAnimatedGeometryRoot(aList, &lastAnimatedGeometryRoot)) {
+    if (ChooseAnimatedGeometryRoot(*aList, &lastAnimatedGeometryRoot)) {
       topLeft = lastAnimatedGeometryRoot->GetOffsetToCrossDoc(mContainerReferenceFrame);
     }
   }
@@ -2446,7 +2472,42 @@ ContainerState::ProcessDisplayItems(const nsDisplayList& aList,
   int32_t maxLayers = nsDisplayItem::MaxActiveLayers();
   int layerCount = 0;
 
-  for (nsDisplayItem* item = aList.GetBottom(); item; item = item->GetAbove()) {
+  nsDisplayList savedItems;
+  nsDisplayItem* item;
+  while ((item = aList->RemoveBottom()) != nullptr) {
+    // Peek ahead to the next item and try merging with it or swapping with it
+    // if necessary.
+    nsDisplayItem* aboveItem;
+    while ((aboveItem = aList->GetBottom()) != nullptr) {
+      if (aboveItem->TryMerge(mBuilder, item)) {
+        aList->RemoveBottom();
+        item->~nsDisplayItem();
+        item = aboveItem;
+      } else if (IsScrollLayerItemAndOverlayScrollbarForScrollFrame(aboveItem, item)) {
+        // If an overlay scrollbar item is between a scroll layer item and the
+        // other scroll layer items that we need to merge with just move the
+        // scrollbar item up, that way it will be on top of the scrolled content
+        // and we can try to merge all the scroll layer items.
+        aList->RemoveBottom();
+        aList->AppendToBottom(item);
+        item = aboveItem;
+      } else {
+        break;
+      }
+    }
+
+    nsDisplayList* itemSameCoordinateSystemChildren
+      = item->GetSameCoordinateSystemChildren();
+    if (itemSameCoordinateSystemChildren) {
+      if (item->ShouldFlattenAway(mBuilder)) {
+        aList->AppendToBottom(itemSameCoordinateSystemChildren);
+        item->~nsDisplayItem();
+        continue;
+      }
+    }
+
+    savedItems.AppendToTop(item);
+
     NS_ASSERTION(mAppUnitsPerDevPixel == AppUnitsPerDevPixel(item),
       "items in a container layer should all have the same app units per dev pixel");
 
@@ -2667,6 +2728,8 @@ ContainerState::ProcessDisplayItems(const nsDisplayList& aList,
       }
     }
   }
+
+  aList->AppendToTop(&savedItems);
 }
 
 void
@@ -3313,7 +3376,7 @@ FrameLayerBuilder::BuildContainerLayerFor(nsDisplayListBuilder* aBuilder,
                                           LayerManager* aManager,
                                           nsIFrame* aContainerFrame,
                                           nsDisplayItem* aContainerItem,
-                                          const nsDisplayList& aChildren,
+                                          nsDisplayList* aChildren,
                                           const ContainerLayerParameters& aParameters,
                                           const gfx3DMatrix* aTransform,
                                           uint32_t aFlags)
@@ -3377,7 +3440,7 @@ FrameLayerBuilder::BuildContainerLayerFor(nsDisplayListBuilder* aBuilder,
     // early exit because later, invalidation will walk up the frame tree to
     // determine which thebes layer gets invalidated. Since an empty layer
     // should never have anything to paint, it should never be invalidated.
-    NS_ASSERTION(aChildren.IsEmpty(), "Should have no children");
+    NS_ASSERTION(aChildren->IsEmpty(), "Should have no children");
     return containerLayer.forget();
   }
 
@@ -3445,7 +3508,7 @@ FrameLayerBuilder::BuildContainerLayerFor(nsDisplayListBuilder* aBuilder,
     break;
   }
 
-  NS_ASSERTION(bounds.IsEqualInterior(aChildren.GetBounds(aBuilder)), "Wrong bounds");
+  NS_ASSERTION(bounds.IsEqualInterior(aChildren->GetBounds(aBuilder)), "Wrong bounds");
   pixBounds.MoveBy(nsIntPoint(scaleParameters.mOffset.x, scaleParameters.mOffset.y));
   if (aParameters.mAncestorClipRect && !(aFlags & CONTAINER_NOT_CLIPPED_BY_ANCESTORS)) {
     SetVisibleRegionForLayer(containerLayer, nsIntRegion(pixBounds),
@@ -3455,7 +3518,7 @@ FrameLayerBuilder::BuildContainerLayerFor(nsDisplayListBuilder* aBuilder,
   }
   // Make sure that rounding the visible region out didn't add any area
   // we won't paint
-  if (aChildren.IsOpaque() && !aChildren.NeedsTransparentSurface()) {
+  if (aChildren->IsOpaque() && !aChildren->NeedsTransparentSurface()) {
     bounds.ScaleRoundIn(scaleParameters.mXScale, scaleParameters.mYScale);
     if (bounds.Contains(pixBounds.ToAppUnits(appUnitsPerDevPixel))) {
       // Clear CONTENT_COMPONENT_ALPHA

layout/base/FrameLayerBuilder.h

@@ -207,13 +207,14 @@ public:
    * is set based on what's in the layer.
    * The container layer is transformed by aTransform (if non-null), and
    * the result is transformed by the scale factors in aContainerParameters.
+   * aChildren is modified due to display item merging and flattening.
    */
   already_AddRefed<ContainerLayer>
   BuildContainerLayerFor(nsDisplayListBuilder* aBuilder,
                          LayerManager* aManager,
                          nsIFrame* aContainerFrame,
                          nsDisplayItem* aContainerItem,
-                         const nsDisplayList& aChildren,
+                         nsDisplayList* aChildren,
                          const ContainerLayerParameters& aContainerParameters,
                          const gfx3DMatrix* aTransform,
                          uint32_t aFlags = 0);

layout/base/nsDisplayList.cpp

@@ -1235,10 +1235,9 @@ nsDisplayList::ComputeVisibilityForSublist(nsDisplayListBuilder* aBuilder,
 
 void nsDisplayList::PaintRoot(nsDisplayListBuilder* aBuilder,
                               nsRenderingContext* aCtx,
-                              uint32_t aFlags) const {
+                              uint32_t aFlags) {
   PROFILER_LABEL("nsDisplayList", "PaintRoot",
     js::ProfileEntry::Category::GRAPHICS);
-
   PaintForFrame(aBuilder, aCtx, aBuilder->RootReferenceFrame(), aFlags);
 }
 
@@ -1250,7 +1249,7 @@ void nsDisplayList::PaintRoot(nsDisplayListBuilder* aBuilder,
 void nsDisplayList::PaintForFrame(nsDisplayListBuilder* aBuilder,
                                   nsRenderingContext* aCtx,
                                   nsIFrame* aForFrame,
-                                  uint32_t aFlags) const {
+                                  uint32_t aFlags) {
   NS_ASSERTION(mDidComputeVisibility,
                "Must call ComputeVisibility before calling Paint");
 
@@ -1322,7 +1321,7 @@ void nsDisplayList::PaintForFrame(nsDisplayListBuilder* aBuilder,
   ContainerLayerParameters containerParameters
     (presShell->GetXResolution(), presShell->GetYResolution());
   nsRefPtr<ContainerLayer> root = layerBuilder->
-    BuildContainerLayerFor(aBuilder, layerManager, aForFrame, nullptr, *this,
+    BuildContainerLayerFor(aBuilder, layerManager, aForFrame, nullptr, this,
                            containerParameters, nullptr);
 
   nsIDocument* document = nullptr;
@@ -3291,7 +3290,7 @@ nsDisplayOpacity::BuildLayer(nsDisplayListBuilder* aBuilder,
     return nullptr;
   }
   nsRefPtr<Layer> container = aManager->GetLayerBuilder()->
-    BuildContainerLayerFor(aBuilder, aManager, mFrame, this, mList,
+    BuildContainerLayerFor(aBuilder, aManager, mFrame, this, &mList,
                            aContainerParameters, nullptr);
   if (!container)
     return nullptr;
@@ -3454,7 +3453,7 @@ nsDisplayMixBlendMode::BuildLayer(nsDisplayListBuilder* aBuilder,
   newContainerParameters.mDisableSubpixelAntialiasingInDescendants = true;
 
   nsRefPtr<Layer> container = aManager->GetLayerBuilder()->
-  BuildContainerLayerFor(aBuilder, aManager, mFrame, this, mList,
+  BuildContainerLayerFor(aBuilder, aManager, mFrame, this, &mList,
                          newContainerParameters, nullptr);
   if (!container) {
     return nullptr;
@@ -3531,7 +3530,7 @@ nsDisplayBlendContainer::BuildLayer(nsDisplayListBuilder* aBuilder,
   newContainerParameters.mDisableSubpixelAntialiasingInDescendants = true;
 
   nsRefPtr<Layer> container = aManager->GetLayerBuilder()->
-  BuildContainerLayerFor(aBuilder, aManager, mFrame, this, mList,
+  BuildContainerLayerFor(aBuilder, aManager, mFrame, this, &mList,
                          newContainerParameters, nullptr);
   if (!container) {
     return nullptr;
@@ -3576,7 +3575,7 @@ nsDisplayOwnLayer::BuildLayer(nsDisplayListBuilder* aBuilder,
                               LayerManager* aManager,
                               const ContainerLayerParameters& aContainerParameters) {
   nsRefPtr<ContainerLayer> layer = aManager->GetLayerBuilder()->
-    BuildContainerLayerFor(aBuilder, aManager, mFrame, this, mList,
+    BuildContainerLayerFor(aBuilder, aManager, mFrame, this, &mList,
                            aContainerParameters, nullptr);
   if (mFlags & VERTICAL_SCROLLBAR) {
     layer->SetScrollbarData(mScrollTarget, Layer::ScrollDirection::VERTICAL);
@@ -3899,7 +3898,7 @@ nsDisplayScrollLayer::BuildLayer(nsDisplayListBuilder* aBuilder,
                                  LayerManager* aManager,
                                  const ContainerLayerParameters& aContainerParameters) {
   nsRefPtr<ContainerLayer> layer = aManager->GetLayerBuilder()->
-    BuildContainerLayerFor(aBuilder, aManager, mFrame, this, mList,
+    BuildContainerLayerFor(aBuilder, aManager, mFrame, this, &mList,
                            aContainerParameters, nullptr);
 
   nsRect viewport = mScrollFrame->GetRect() -
@@ -4803,7 +4802,7 @@ already_AddRefed<Layer> nsDisplayTransform::BuildLayer(nsDisplayListBuilder *aBu
   uint32_t flags = ShouldPrerenderTransformedContent(aBuilder, mFrame, false) ?
     FrameLayerBuilder::CONTAINER_NOT_CLIPPED_BY_ANCESTORS : 0;
   nsRefPtr<ContainerLayer> container = aManager->GetLayerBuilder()->
-    BuildContainerLayerFor(aBuilder, aManager, mFrame, this, *mStoredList.GetChildren(),
+    BuildContainerLayerFor(aBuilder, aManager, mFrame, this, mStoredList.GetChildren(),
                            aContainerParameters, &newTransformMatrix, flags);
 
   if (!container) {
@@ -5327,7 +5326,7 @@ nsDisplaySVGEffects::BuildLayer(nsDisplayListBuilder* aBuilder,
   }
 
   nsRefPtr<ContainerLayer> container = aManager->GetLayerBuilder()->
-    BuildContainerLayerFor(aBuilder, aManager, mFrame, this, mList,
+    BuildContainerLayerFor(aBuilder, aManager, mFrame, this, &mList,
                            newContainerParameters, nullptr);
 
   return container.forget();

layout/base/nsDisplayList.h

@@ -1681,13 +1681,13 @@ public:
     PAINT_COMPRESSED = 0x10
   };
   void PaintRoot(nsDisplayListBuilder* aBuilder, nsRenderingContext* aCtx,
-                 uint32_t aFlags) const;
+                 uint32_t aFlags);
   /**
    * Like PaintRoot, but used for internal display sublists.
    * aForFrame is the frame that the list is associated with.
    */
   void PaintForFrame(nsDisplayListBuilder* aBuilder, nsRenderingContext* aCtx,
-                     nsIFrame* aForFrame, uint32_t aFlags) const;
+                     nsIFrame* aForFrame, uint32_t aFlags);
   /**
    * Get the bounds. Takes the union of the bounds of all children.
    */