Bug 564991. Part 9: Retain layer trees. r=tnikkel,sr=mats

gfx/layers/Layers.h

@@ -160,16 +160,24 @@ public:
    * The callee must draw all of aRegionToDraw. Drawing outside
    * aRegionToDraw will be clipped out or ignored.
    * The callee must draw all of aRegionToDraw.
+   * This region is relative to 0,0 in the ThebesLayer.
    * 
    * aRegionToInvalidate contains a region whose contents have been
    * changed by the layer manager and which must therefore be invalidated.
-   * For example, this could be non-empty if the layer internally switched
-   * from RGBA to RGB or back ... we might want to repaint it to
+   * For example, this could be non-empty if a retained layer internally
+   * switches from RGBA to RGB or back ... we might want to repaint it to
    * consistently use subpixel-AA or not.
+   * This region is relative to 0,0 in the ThebesLayer.
+   * aRegionToInvalidate may contain areas that are outside
+   * aRegionToDraw; the callee must ensure that these areas are repainted
+   * in the current layer manager transaction or in a later layer
+   * manager transaction.
    * 
    * aContext must not be used after the call has returned.
    * We guarantee that buffered contents in the visible
    * region are valid once drawing is complete.
+   * 
+   * The origin of aContext is 0,0 in the ThebesLayer.
    */
   typedef void (* DrawThebesLayerCallback)(ThebesLayer* aLayer,
                                            gfxContext* aContext,

layout/base/FrameLayerBuilder.h

@@ -38,38 +38,113 @@
 #ifndef FRAMELAYERBUILDER_H_
 #define FRAMELAYERBUILDER_H_
 
-#include "Layers.h"
+#include "nsTHashtable.h"
+#include "nsHashKeys.h"
+#include "nsTArray.h"
+#include "nsRegion.h"
+#include "nsIFrame.h"
 
 class nsDisplayListBuilder;
 class nsDisplayList;
 class nsDisplayItem;
-class nsIFrame;
-class nsRect;
-class nsIntRegion;
 class gfxContext;
 
 namespace mozilla {
 
+namespace layers {
+class Layer;
+class ThebesLayer;
+class LayerManager;
+}
+
+/**
+ * The FrameLayerBuilder belongs to an nsDisplayListBuilder and is
+ * responsible for converting display lists into layer trees.
+ * 
+ * The most important API in this class is BuildContainerLayerFor. This
+ * method takes a display list as input and constructs a ContainerLayer
+ * with child layers that render the contents of the display list. It
+ * also updates userdata for the retained layer manager, and
+ * DisplayItemDataProperty data for frames, to record the relationship
+ * between frames and layers.
+ * 
+ * That data enables us to retain layer trees. When constructing a
+ * ContainerLayer, we first check to see if there's an existing
+ * ContainerLayer for the same frame that can be recycled. If we recycle
+ * it, we also try to reuse its existing ThebesLayer children to render
+ * the display items without layers of their own. The idea is that by
+ * recycling layers deterministically, we can ensure that when nothing
+ * changes in a display list, we will reuse the existing layers without
+ * changes.
+ * 
+ * We expose a GetLeafLayerFor method that can be called by display items
+ * that make their own layers (e.g. canvas and video); this method
+ * locates the last layer used to render the display item, if any, and
+ * return it as a candidate for recycling.
+ * 
+ * FrameLayerBuilder sets up ThebesLayers so that 0,0 in the Thebes layer
+ * corresponds to the (pixel-snapped) top-left of the aActiveScrolledRoot.
+ * It sets up ContainerLayers so that 0,0 in the container layer
+ * corresponds to the snapped top-left of the display list reference frame.
+ */
 class FrameLayerBuilder {
 public:
-  typedef mozilla::layers::Layer Layer;
-  typedef mozilla::layers::ThebesLayer ThebesLayer;
-  typedef mozilla::layers::LayerManager LayerManager;
+  typedef layers::Layer Layer; 
+  typedef layers::ThebesLayer ThebesLayer;
+  typedef layers::LayerManager LayerManager;
+
+  FrameLayerBuilder() :
+    mRetainingManager(nsnull),
+    mInvalidateAllThebesContent(PR_FALSE),
+    mInvalidateAllLayers(PR_FALSE)
+  {
+    mNewDisplayItemData.Init();
+    mThebesLayerItems.Init();
+  }
 
   /**
-   * Get a container layer for a display item that contains a child
-   * list, either reusing an existing one or creating a new one.
-   * aContainer may be null, in which case we construct a root layer.
+   * Call this to register a layer tree which was retained since the last
+   * paint.
    */
-  already_AddRefed<Layer> GetContainerLayerFor(nsDisplayListBuilder* aBuilder,
-                                               LayerManager* aManager,
-                                               nsDisplayItem* aContainer,
-                                               const nsDisplayList& aChildren);
+  void BeginUpdatingRetainedLayers(LayerManager* aManager);
 
   /**
-   * Get a retained layer for a leaf display item. Returns null if no
-   * layer is available, in which case the caller will probably need to
-   * create one.
+   * Call this whenever we end a transaction on aManager. If aManager
+   * is not the retained layer manager then it must be a temporary layer
+   * manager that will not be used again.
+   */
+  void DidEndTransaction(LayerManager* aManager);
+
+  /**
+   * Build a container layer for a display item that contains a child
+   * list, either reusing an existing one or creating a new one. It
+   * sets the container layer children to layers which together render
+   * the contents of the display list. It reuses existing layers from
+   * the retained layer manager if possible.
+   * aContainer may be null, in which case we construct a root layer.
+   * This gets called by display list code. It calls BuildLayer on the
+   * items in the display list, making items with their own layers
+   * children of the new container, and assigning all other items to
+   * ThebesLayer children created and managed by the FrameLayerBuilder.
+   * Returns a layer with clip rect cleared; it is the
+   * caller's responsibility to add any clip rect and set the visible
+   * region.
+   */
+  already_AddRefed<Layer> BuildContainerLayerFor(nsDisplayListBuilder* aBuilder,
+                                                 LayerManager* aManager,
+                                                 nsIFrame* aContainerFrame,
+                                                 nsDisplayItem* aContainerItem,
+                                                 const nsDisplayList& aChildren);
+
+  /**
+   * Get a retained layer for a display item that needs to create its own
+   * layer for rendering (i.e. under nsDisplayItem::BuildLayer). Returns
+   * null if no retained layer is available, which usually means that this
+   * display item didn't have a layer before so the caller will
+   * need to create one.
+   * Returns a layer with clip rect cleared; it is the
+   * caller's responsibility to add any clip rect and set the visible
+   * region.
    */
   Layer* GetLeafLayerFor(nsDisplayListBuilder* aBuilder,
                          LayerManager* aManager,
@@ -84,6 +159,18 @@ public:
   static void InvalidateThebesLayerContents(nsIFrame* aFrame,
                                             const nsRect& aRect);
 
+  /**
+   * Call this to force *all* retained layer contents to be discarded at
+   * the next paint.
+   */
+  static void InvalidateAllThebesLayerContents(LayerManager* aManager);
+
+  /**
+   * Call this to force all retained layers to be discarded and recreated at
+   * the next paint.
+   */
+  static void InvalidateAllLayers(LayerManager* aManager);
+  
   /**
    * This callback must be provided to EndTransaction. The callback data
    * must be the nsDisplayListBuilder containing this FrameLayerBuilder.
@@ -93,6 +180,173 @@ public:
                               const nsIntRegion& aRegionToDraw,
                               const nsIntRegion& aRegionToInvalidate,
                               void* aCallbackData);
+
+#ifdef DEBUG
+  /**
+   * Dumps aManager's layer tree to stderr.
+   */
+  static void DumpLayerTree(LayerManager* aManager);
+
+  /**
+   * Dumps this FrameLayerBuilder's retained layer manager's retained
+   * layer tree to stderr.
+   */
+  void DumpRetainedLayerTree();
+#endif
+
+  /******* PRIVATE METHODS to FrameLayerBuilder.cpp ********/
+  /* These are only in the public section because they need
+   * to be called by file-scope helper functions in FrameLayerBuilder.cpp.
+   */
+  
+  /**
+   * Record aItem as a display item that is rendered by aLayer.
+   */
+  void AddLayerDisplayItem(Layer* aLayer, nsDisplayItem* aItem);
+
+  /**
+   * Record aItem as a display item that is rendered by the ThebesLayer
+   * aLayer, with aClipRect, where aContainerLayerFrame is the frame
+   * for the container layer this ThebesItem belongs to.
+   * aItem must have an underlying frame.
+   */
+  void AddThebesDisplayItem(ThebesLayer* aLayer, nsDisplayItem* aItem,
+                            const nsRect* aClipRect,
+                            nsIFrame* aContainerLayerFrame);
+
+  /**
+   * Given a frame and a display item key that uniquely identifies a
+   * display item for the frame, find the layer that was last used to
+   * render that display item. Returns null if there is no such layer.
+   * This could be a dedicated layer for the display item, or a ThebesLayer
+   * that renders many display items.
+   */
+  Layer* GetOldLayerFor(nsIFrame* aFrame, PRUint32 aDisplayItemKey);
+
+protected:
+  /**
+   * We store an array of these for each frame that is associated with
+   * one or more retained layers. Each DisplayItemData records the layer
+   * used to render one of the frame's display items.
+   */
+  class DisplayItemData {
+  public:
+    DisplayItemData(Layer* aLayer, PRUint32 aKey)
+      : mLayer(aLayer), mDisplayItemKey(aKey) {}
+
+    nsRefPtr<Layer> mLayer;
+    PRUint32        mDisplayItemKey;
+  };
+
+  static void InternalDestroyDisplayItemData(nsIFrame* aFrame,
+                                             void* aPropertyValue,
+                                             PRBool aRemoveFromFramesWithLayers);
+  static void DestroyDisplayItemData(nsIFrame* aFrame, void* aPropertyValue);
+
+  /**
+   * For DisplayItemDataProperty, the property value *is* an
+   * nsTArray<DisplayItemData>, not a pointer to an array. This works
+   * because sizeof(nsTArray<T>) == sizeof(void*).
+   */
+  NS_DECLARE_FRAME_PROPERTY_WITH_FRAME_IN_DTOR(DisplayItemDataProperty,
+                                               DestroyDisplayItemData)
+
+  /**
+   * We accumulate DisplayItemData elements in a hashtable during
+   * the paint process, and store them in the frame property only when
+   * paint is complete. This is the hashentry for that hashtable.
+   */
+  class DisplayItemDataEntry : public nsPtrHashKey<nsIFrame> {
+  public:
+    DisplayItemDataEntry(const nsIFrame *key) : nsPtrHashKey<nsIFrame>(key) {}
+    DisplayItemDataEntry(const DisplayItemDataEntry &toCopy) :
+      nsPtrHashKey<nsIFrame>(toCopy.mKey), mData(toCopy.mData)
+    {
+      NS_ERROR("Should never be called, since we ALLOW_MEMMOVE");
+    }
+
+    PRBool HasContainerLayer();
+
+    nsTArray<DisplayItemData> mData;
+
+    enum { ALLOW_MEMMOVE = PR_TRUE };
+  };
+
+  /**
+   * We store one of these for each display item associated with a
+   * ThebesLayer, in a hashtable that maps each ThebesLayer to an array
+   * of ClippedDisplayItems. (ThebesLayerItemsEntry is the hash entry
+   * for that hashtable.)
+   * These are only stored during the paint process, so that the
+   * DrawThebesLayer callback can figure out which items to draw for the
+   * ThebesLayer.
+   * mItem always has an underlying frame.
+   */
+  struct ClippedDisplayItem {
+    ClippedDisplayItem(nsDisplayItem* aItem, const nsRect* aClipRect)
+      : mItem(aItem), mHasClipRect(aClipRect != nsnull)
+    {
+      if (mHasClipRect) {
+        mClipRect = *aClipRect;
+      }
+    }
+
+    nsDisplayItem* mItem;
+    nsRect         mClipRect;
+    PRPackedBool   mHasClipRect;
+  };
+
+  /**
+   * We accumulate ClippedDisplayItem elements in a hashtable during
+   * the paint process. This is the hashentry for that hashtable.
+   */
+  class ThebesLayerItemsEntry : public nsPtrHashKey<ThebesLayer> {
+  public:
+    ThebesLayerItemsEntry(const ThebesLayer *key) : nsPtrHashKey<ThebesLayer>(key) {}
+    ThebesLayerItemsEntry(const ThebesLayerItemsEntry &toCopy) :
+      nsPtrHashKey<ThebesLayer>(toCopy.mKey), mItems(toCopy.mItems)
+    {
+      NS_ERROR("Should never be called, since we ALLOW_MEMMOVE");
+    }
+
+    nsTArray<ClippedDisplayItem> mItems;
+    nsIFrame* mContainerLayerFrame;
+
+    enum { ALLOW_MEMMOVE = PR_TRUE };
+  };
+
+  void RemoveThebesItemsForLayerSubtree(Layer* aLayer);
+
+  static PLDHashOperator UpdateDisplayItemDataForFrame(nsPtrHashKey<nsIFrame>* aEntry,
+                                                       void* aUserArg);
+  static PLDHashOperator StoreNewDisplayItemData(DisplayItemDataEntry* aEntry,
+                                                 void* aUserArg);
+
+  /**
+   * The layer manager belonging to the widget that is being retained
+   * across paints.
+   */
+  LayerManager*                       mRetainingManager;
+  /**
+   * A map from frames to a list of (display item key, layer) pairs that
+   * describes what layers various parts of the frame are assigned to.
+   */
+  nsTHashtable<DisplayItemDataEntry>  mNewDisplayItemData;
+  /**
+   * A map from ThebesLayers to the list of display items (plus
+   * clipping data) to be rendered in the layer.
+   */
+  nsTHashtable<ThebesLayerItemsEntry> mThebesLayerItems;
+  /**
+   * Indicates that the contents of all ThebesLayers should be rerendered
+   * during this paint.
+   */
+  PRPackedBool                        mInvalidateAllThebesContent;
+  /**
+   * Indicates that the entire layer tree should be rerendered
+   * during this paint.
+   */
+  PRPackedBool                        mInvalidateAllLayers;
 };
 
 }

layout/base/nsDisplayList.cpp

@@ -453,7 +453,7 @@ void nsDisplayList::PaintForFrame(nsDisplayListBuilder* aBuilder,
   }
 
   nsRefPtr<Layer> root = aBuilder->LayerBuilder()->
-    GetContainerLayerFor(aBuilder, layerManager, nsnull, *this);
+    BuildContainerLayerFor(aBuilder, layerManager, aForFrame, nsnull, *this);
   if (!root)
     return;
 
@@ -464,6 +464,7 @@ void nsDisplayList::PaintForFrame(nsDisplayListBuilder* aBuilder,
   layerManager->SetRoot(root);
   layerManager->EndTransaction(FrameLayerBuilder::DrawThebesLayer,
                                aBuilder);
+  aBuilder->LayerBuilder()->DidEndTransaction(layerManager);
 
   nsCSSRendering::DidPaint();
 }
@@ -639,6 +640,24 @@ void nsDisplayList::Sort(nsDisplayListBuilder* aBuilder,
   ::Sort(this, Count(), aCmp, aClosure);
 }
 
+PRBool nsDisplayItem::RecomputeVisibility(nsDisplayListBuilder* aBuilder,
+                                          nsRegion* aVisibleRegion) {
+  nsRect bounds = GetBounds(aBuilder);
+
+  nsRegion itemVisible;
+  itemVisible.And(*aVisibleRegion, bounds);
+  mVisibleRect = itemVisible.GetBounds();
+
+  if (mVisibleRect.IsEmpty() ||
+      !ComputeVisibility(aBuilder, aVisibleRegion, nsnull))
+    return PR_FALSE;
+
+  if (IsOpaque(aBuilder)) {
+    aVisibleRegion->Sub(*aVisibleRegion, bounds);
+  }
+  return PR_TRUE;
+}
+
 void nsDisplaySolidColor::Paint(nsDisplayListBuilder* aBuilder,
                                 nsIRenderingContext* aCtx) {
   aCtx->SetColor(mColor);
@@ -1147,7 +1166,7 @@ already_AddRefed<Layer>
 nsDisplayOpacity::BuildLayer(nsDisplayListBuilder* aBuilder,
                              LayerManager* aManager) {
   nsRefPtr<Layer> layer = aBuilder->LayerBuilder()->
-    GetContainerLayerFor(aBuilder, aManager, this, mList);
+    BuildContainerLayerFor(aBuilder, aManager, mFrame, this, mList);
   if (!layer)
     return nsnull;
 

layout/base/nsDisplayList.h

@@ -643,7 +643,17 @@ public:
 #endif
 
   nsDisplayItem* GetAbove() { return mAbove; }
-  
+
+  /**
+   * Like ComputeVisibility, but does the work that nsDisplayList
+   * does per-item:
+   * -- Intersects GetBounds with aVisibleRegion and puts the result
+   * in mVisibleRect
+   * -- Subtracts bounds from aVisibleRegion if the item is opaque
+   */
+  PRBool RecomputeVisibility(nsDisplayListBuilder* aBuilder,
+                             nsRegion* aVisibleRegion);
+
 protected:
   friend class nsDisplayList;
   

layout/base/nsLayoutUtils.cpp

@@ -677,6 +677,20 @@ nsLayoutUtils::GetScrollableFrameFor(nsIFrame *aScrolledFrame)
   return sf;
 }
 
+nsIFrame*
+nsLayoutUtils::GetActiveScrolledRootFor(nsIFrame* aFrame,
+                                        nsIFrame* aStopAtAncestor,
+                                        nsPoint* aOffset)
+{
+  // For now, just use aStopAtAncestor --- i.e., treat nothing as active.
+  // We'll make this more precise when we actually start using layers for
+  // scrolling.
+  if (aOffset) {
+    *aOffset = aFrame->GetOffsetTo(aStopAtAncestor);
+  }
+  return aStopAtAncestor;
+}
+
 // static
 nsIScrollableFrame*
 nsLayoutUtils::GetNearestScrollableFrameForDirection(nsIFrame* aFrame,

layout/base/nsLayoutUtils.h

@@ -287,6 +287,17 @@ public:
   static PRBool IsAncestorFrameCrossDoc(nsIFrame* aAncestorFrame, nsIFrame* aFrame,
                                         nsIFrame* aCommonAncestor = nsnull);
 
+  /**
+   * Finds the nearest ancestor frame that is the root of an "actively
+   * scrolled" frame subtree, or aStopAtAncestor if there is no
+   * such ancestor before we reach aStopAtAncestor in the ancestor chain.
+   * We expect frames with the same "active scrolled root" to be
+   * scrolled together, so we'll place them in the same ThebesLayer.
+   */
+  static nsIFrame* GetActiveScrolledRootFor(nsIFrame* aFrame,
+                                            nsIFrame* aStopAtAncestor,
+                                            nsPoint* aOffset);
+
   /**
     * GetFrameFor returns the root frame for a view
     * @param aView is the view to return the root frame for

layout/reftests/scrolling/reftest.list

@@ -1,3 +1,4 @@
 HTTP == fixed-1.html fixed-1.html?ref
 HTTP == opacity-mixed-scrolling-1.html opacity-mixed-scrolling-1.html?ref
 HTTP == simple-1.html simple-1.html?ref
+== uncovering-1.html uncovering-1-ref.html

layout/reftests/scrolling/uncovering-1-ref.html

@@ -0,0 +1,23 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<style>
+body {
+  width: 1500px;
+  overflow: hidden;
+}
+div#bottom {
+  position: fixed;
+  left: 0;
+  top: 0;
+  height: 200px;
+  width: 200px;
+  background: green;
+}
+</style>
+</head>
+<body>
+<div id="bottom"></div>
+<div style="width:600px; height:100px; background:pink;"></div>
+</body>
+</html>

layout/reftests/scrolling/uncovering-1.html

@@ -0,0 +1,31 @@
+<!DOCTYPE HTML>
+<html class="reftest-wait">
+<head>
+<style>
+body {
+  width: 1500px;
+  overflow: hidden;
+}
+div#bottom {
+  position: fixed;
+  left: 0;
+  top: 0;
+  height: 200px;
+  width: 200px;
+  background: green;
+}
+</style>
+</head>
+<body>
+<div id="bottom"></div>
+<div style="width:600px; height:100px; background:pink;"></div>
+<script>
+document.documentElement.scrollLeft = 200;
+function doTest() {
+  document.documentElement.removeAttribute("class");
+  document.documentElement.scrollLeft = 0;
+}
+window.addEventListener("MozReftestInvalidate", doTest, false);
+</script>
+</body>
+</html>