1 files changed, 40 insertions, 11 deletions

diff --git a/layout/painting/nsDisplayList.h b/layout/painting/nsDisplayList.h
index 5064677cc7..9862415f61 100644
--- a/layout/painting/nsDisplayList.h
+++ b/layout/painting/nsDisplayList.h
@@ -659,7 +659,7 @@ class nsDisplayListBuilder {
    * Get the frame that the caret is supposed to draw in.
    * If the caret is currently invisible, this will be null.
    */
-  nsIFrame* GetCaretFrame() { return mCaretFrame; }
+  nsIFrame* GetCaretFrame() { return CurrentPresShellState()->mCaretFrame; }
   /**
    * Get the rectangle we're supposed to draw the caret into.
    */
@@ -852,9 +852,9 @@ class nsDisplayListBuilder {
   /**
    * Notifies the builder that a particular themed widget exists
    * at the given rectangle within the currently built display list.
-   * For certain appearance values (currently only StyleAppearance::Toolbar and
-   * StyleAppearance::WindowTitlebar) this gets called during every display list
-   * construction, for every themed widget of the right type within the
+   * For certain appearance values (currently only
+   * StyleAppearance::MozWindowTitlebar) this gets called during every display
+   * list construction, for every themed widget of the right type within the
    * display list, except for themed widgets which are transformed or have
    * effects applied to them (e.g. CSS opacity or filters).
    *
@@ -904,6 +904,11 @@ class nsDisplayListBuilder {
                        const dom::EffectsInfo& aUpdate);
 
   /**
+   * Invalidates the caret frames from previous paints, if they have changed.
+   */
+  void InvalidateCaretFramesIfNeeded();
+
+  /**
    * Allocate memory in our arena. It will only be freed when this display list
    * builder is destroyed. This memory holds nsDisplayItems and
    * DisplayItemClipChain objects.
@@ -1729,6 +1734,7 @@ class nsDisplayListBuilder {
     bool mInsidePointerEventsNoneDoc;
     bool mTouchEventPrefEnabledDoc;
     nsIFrame* mPresShellIgnoreScrollFrame;
+    nsIFrame* mCaretFrame = nullptr;
   };
 
   PresShellState* CurrentPresShellState() {
@@ -1763,7 +1769,6 @@ class nsDisplayListBuilder {
   // The reference frame for mCurrentFrame.
   const nsIFrame* mCurrentReferenceFrame;
 
-  nsIFrame* mCaretFrame;
   // A temporary list that we append scroll info items to while building
   // display items for the contents of frames with SVG effects.
   // Only non-null when ShouldBuildScrollInfoItemsForHoisting() is true.
@@ -1808,6 +1813,9 @@ class nsDisplayListBuilder {
   // Stores reusable items collected during display list preprocessing.
   nsTHashSet<nsDisplayItem*> mReuseableItems;
 
+  // Tracked carets used for retained display list.
+  AutoTArray<RefPtr<nsCaret>, 1> mPaintedCarets;
+
   // Tracked regions used for retained display list.
   WeakFrameRegion mRetainedWindowDraggingRegion;
   WeakFrameRegion mRetainedWindowNoDraggingRegion;
@@ -3195,12 +3203,13 @@ class nsDisplayList {
     // array of 20 items should be able to avoid a lot of dynamic allocations
     // here.
     AutoTArray<Item, 20> items;
+    // Ensure we need just one alloc otherwise, no-op if enough.
+    items.SetCapacity(Length());
 
     for (nsDisplayItem* item : TakeItems()) {
       items.AppendElement(Item(item));
     }
-
-    std::stable_sort(items.begin(), items.end(), aComparator);
+    items.StableSort(aComparator);
 
     for (Item& item : items) {
       AppendToTop(item);
@@ -3208,6 +3217,7 @@ class nsDisplayList {
   }
 
   nsDisplayList TakeItems() {
+    // This std::move makes this a defined empty list, see assignment operator.
     nsDisplayList list = std::move(*this);
 #ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
     list.mAllowNonEmptyDestruction = true;
@@ -5465,7 +5475,7 @@ class nsDisplayOwnLayer : public nsDisplayWrapList {
   bool IsFixedPositionLayer() const;
   bool IsStickyPositionLayer() const;
   bool HasDynamicToolbar() const;
-  virtual bool ShouldGetFixedOrStickyAnimationId() { return false; }
+  virtual bool ShouldGetFixedAnimationId() { return false; }
 
   bool CreatesStackingContextHelper() override { return true; }
 
@@ -5481,6 +5491,16 @@ class nsDisplayOwnLayer : public nsDisplayWrapList {
    */
   layers::ScrollbarData mScrollbarData;
   bool mForceActive;
+
+  // Used for APZ to animate this layer for purposes such as
+  // pinch-zooming or scrollbar thumb movement. Note that setting this
+  // creates a WebRender ReferenceFrame spatial node, and should only
+  // be used for display items that establish a Gecko reference frame
+  // as well (or leaf items like scrollbar thumb nodes where it does not
+  // matter).
+  // FIXME: This is currently also used for adjusting position:fixed items
+  // for dynamic toolbar movement. This may be a problem as position:fixed
+  // items do not establish Gecko reference frames.
   uint64_t mWrAnimationId;
 };
 
@@ -5540,7 +5560,8 @@ class nsDisplayStickyPosition : public nsDisplayOwnLayer {
       : nsDisplayOwnLayer(aBuilder, aOther),
         mContainerASR(aOther.mContainerASR),
         mClippedToDisplayPort(aOther.mClippedToDisplayPort),
-        mShouldFlatten(false) {
+        mShouldFlatten(false),
+        mWrStickyAnimationId(0) {
     MOZ_COUNT_CTOR(nsDisplayStickyPosition);
   }
 
@@ -5565,7 +5586,6 @@ class nsDisplayStickyPosition : public nsDisplayOwnLayer {
 
   bool UpdateScrollData(layers::WebRenderScrollData* aData,
                         layers::WebRenderLayerScrollData* aLayerData) override;
-  bool ShouldGetFixedOrStickyAnimationId() override;
 
   const ActiveScrolledRoot* GetContainerASR() const { return mContainerASR; }
 
@@ -5581,6 +5601,8 @@ class nsDisplayStickyPosition : public nsDisplayOwnLayer {
     return mShouldFlatten;
   }
 
+  bool ShouldGetStickyAnimationId() const;
+
  private:
   NS_DISPLAY_ALLOW_CLONING()
 
@@ -5610,6 +5632,13 @@ class nsDisplayStickyPosition : public nsDisplayOwnLayer {
 
   // True if this item should be flattened away.
   bool mShouldFlatten;
+
+  // Used for APZ to animate the sticky element in the compositor
+  // for purposes such as dynamic toolbar movement and (in the future)
+  // overscroll-related adjustment. Unlike nsDisplayOwnLayer::mWrAnimationId,
+  // this does not create a WebRender ReferenceFrame, which is important
+  // because sticky elements do not establish Gecko reference frames either.
+  uint64_t mWrStickyAnimationId;
 };
 
 class nsDisplayFixedPosition : public nsDisplayOwnLayer {
@@ -5651,7 +5680,7 @@ class nsDisplayFixedPosition : public nsDisplayOwnLayer {
       nsDisplayListBuilder* aDisplayListBuilder) override;
   bool UpdateScrollData(layers::WebRenderScrollData* aData,
                         layers::WebRenderLayerScrollData* aLayerData) override;
-  bool ShouldGetFixedOrStickyAnimationId() override;
+  bool ShouldGetFixedAnimationId() override;
   void WriteDebugInfo(std::stringstream& aStream) override;
 
  protected: