Bug 1376538 - Transmit APZ focus target updates on empty transactions. r=kats

This commit also schedules empty transactions on input events that trigger a
focus sequence number update.

MozReview-Commit-ID: 1FWXfStLsGv

--HG--
extra : rebase_source : 02c6f07287b6909493f6f88345a3cca93ab3e45b

layout/base/PresShell.cpp

@@ -802,7 +802,6 @@ nsIPresShell::nsIPresShell()
     , mObservingLayoutFlushes(false)
     , mNeedThrottledAnimationFlush(true)
     , mPresShellId(0)
-    , mAPZFocusSequenceNumber(0)
     , mFontSizeInflationEmPerLine(0)
     , mFontSizeInflationMinTwips(0)
     , mFontSizeInflationLineThreshold(0)
@@ -831,6 +830,7 @@ PresShell::PresShell()
   , mLastCallbackEventRequest(nullptr)
   , mLastReflowStart(0.0)
   , mLastAnchorScrollPositionY(0)
+  , mAPZFocusSequenceNumber(0)
   , mChangeNestCount(0)
   , mDocumentLoading(false)
   , mIgnoreFrameDestruction(false)
@@ -6370,6 +6370,10 @@ PresShell::Paint(nsView*         aViewToPaint,
     return;
   }
 
+  // Send an updated focus target with this transaction. Be sure to do this
+  // before we paint in the case this is an empty transaction.
+  layerManager->SetFocusTarget(mAPZFocusTarget);
+
   if (frame) {
     // Try to do an empty transaction, if the frame tree does not
     // need to be updated. Do not try to do an empty transaction on
@@ -7159,8 +7163,10 @@ PresShell::HandleEvent(nsIFrame* aFrame,
 
   // Update the latest focus sequence number with this new sequence number
   if (mAPZFocusSequenceNumber < aEvent->mFocusSequenceNumber) {
-    // XXX should we push a new FocusTarget to APZ here
     mAPZFocusSequenceNumber = aEvent->mFocusSequenceNumber;
+
+    // Schedule an empty transaction to transmit this focus update
+    aFrame->SchedulePaint(nsIFrame::PAINT_COMPOSITE_ONLY);
   }
 
   if (sPointerEventEnabled) {

layout/base/PresShell.h

@@ -862,6 +862,11 @@ protected:
   // when target of pointer event was deleted during executing user handlers.
   nsCOMPtr<nsIContent>      mPointerEventTarget;
 
+  // The focus sequence number of the last processed input event
+  uint64_t                  mAPZFocusSequenceNumber;
+  // The focus information needed for async keyboard scrolling
+  FocusTarget               mAPZFocusTarget;
+
   // This is used to protect ourselves from triggering reflow while in the
   // middle of frame construction and the like... it really shouldn't be
   // needed, one hopes, but it is for now.

layout/base/nsIPresShell.h

@@ -1528,11 +1528,6 @@ public:
 
   uint32_t GetPresShellId() { return mPresShellId; }
 
-  /**
-   * Get the APZ FocusTarget used for async keyboard scrolling.
-   */
-  const FocusTarget& GetAPZFocusTarget() const { return mAPZFocusTarget; }
-
   /**
    * Dispatch a mouse move event based on the most recent mouse position if
    * this PresShell is visible. This is used when the contents of the page
@@ -1905,11 +1900,6 @@ protected:
 
   uint32_t                  mPresShellId;
 
-  // The focus sequence number of the last processed input event
-  uint64_t                  mAPZFocusSequenceNumber;
-  // The focus information needed for async keyboard scrolling
-  FocusTarget               mAPZFocusTarget;
-
   static nsIContent*        gKeyDownTarget;
 
   // Cached font inflation values. This is done to prevent changing of font

layout/painting/nsDisplayList.cpp

@@ -2226,9 +2226,6 @@ already_AddRefed<LayerManager> nsDisplayList::PaintRoot(nsDisplayListBuilder* aB
                            isRootContent, containerParameters));
     }
 
-    // Send an updated focus target with this transaction
-    layerManager->SetFocusTarget(presShell->GetAPZFocusTarget());
-
     // NS_WARNING is debug-only, so don't even bother checking the conditions in
     // a release build.
 #ifdef DEBUG