Bug 563327 part 2. Drive accessibility events off the refresh driver instead of an ad-hoc timer. r=surkov

accessible/src/base/nsEventShell.cpp

@@ -102,7 +102,7 @@ nsCOMPtr<nsINode> nsEventShell::sEventTargetNode;
 ////////////////////////////////////////////////////////////////////////////////
 
 nsAccEventQueue::nsAccEventQueue(nsDocAccessible *aDocument):
-  mProcessingStarted(PR_FALSE), mDocument(aDocument), mFlushingEventsCount(0)
+  mObservingRefresh(PR_FALSE), mDocument(aDocument)
 {
 }
 
@@ -157,6 +157,13 @@ nsAccEventQueue::Push(nsAccEvent *aEvent)
 void
 nsAccEventQueue::Shutdown()
 {
+  if (mObservingRefresh) {
+    nsCOMPtr<nsIPresShell> shell = mDocument->GetPresShell();
+    if (!shell ||
+        shell->RemoveRefreshObserver(this, Flush_Display)) {
+      mObservingRefresh = PR_FALSE;
+    }
+  }
   mDocument = nsnull;
   mEvents.Clear();
 }
@@ -169,14 +176,19 @@ nsAccEventQueue::PrepareFlush()
 {
   // If there are pending events in the queue and events flush isn't planed
   // yet start events flush asynchronously.
-  if (mEvents.Length() > 0 && !mProcessingStarted) {
-    NS_DISPATCH_RUNNABLEMETHOD(Flush, this)
-    mProcessingStarted = PR_TRUE;
+  if (mEvents.Length() > 0 && !mObservingRefresh) {
+    nsCOMPtr<nsIPresShell> shell = mDocument->GetPresShell();
+    // Use a Flush_Display observer so that it will get called after
+    // style and ayout have been flushed.
+    if (shell &&
+        shell->AddRefreshObserver(this, Flush_Display)) {
+      mObservingRefresh = PR_TRUE;
+    }
   }
 }
 
 void
-nsAccEventQueue::Flush()
+nsAccEventQueue::WillRefresh(mozilla::TimeStamp aTime)
 {
   // If the document accessible is now shut down, don't fire events in it
   // anymore.
@@ -187,20 +199,14 @@ nsAccEventQueue::Flush()
   if (!presShell)
     return;
 
-  // Flush layout so that all the frame construction, reflow, and styles are
-  // up-to-date. This will ensure we can get frames for the related nodes, as
-  // well as get the most current information for calculating things like
-  // visibility. We don't flush the display because we don't care about
-  // painting. If no flush is necessary the method will simple return.
-  presShell->FlushPendingNotifications(Flush_Layout);
-
   // Process only currently queued events. Newly appended events during events
   // flushing won't be processed.
-  mFlushingEventsCount = mEvents.Length();
-  NS_ASSERTION(mFlushingEventsCount,
-               "How did we get here without events to fire?");
+  nsTArray < nsRefPtr<nsAccEvent> > events;
+  events.SwapElements(mEvents);
+  PRUint32 length = events.Length();
+  NS_ASSERTION(length, "How did we get here without events to fire?");
 
-  for (PRUint32 index = 0; index < mFlushingEventsCount; index ++) {
+  for (PRUint32 index = 0; index < length; index ++) {
 
     // No presshell means the document was shut down during event handling
     // by AT.
@@ -212,17 +218,12 @@ nsAccEventQueue::Flush()
       mDocument->ProcessPendingEvent(accEvent);
   }
 
-  // Mark we are ready to start event processing again.
-  mProcessingStarted = PR_FALSE;
-
-  // If the document accessible is alive then remove processed events from the
-  // queue (otherwise they were removed on shutdown already) and reinitialize
-  // queue processing callback if necessary (new events might occur duiring
-  // delayed event processing).
-  if (mDocument && mDocument->HasWeakShell()) {
-    mEvents.RemoveElementsAt(0, mFlushingEventsCount);
-    mFlushingEventsCount = 0;
-    PrepareFlush();
+  if (mEvents.Length() == 0) {
+    nsCOMPtr<nsIPresShell> shell = mDocument->GetPresShell();
+    if (!shell ||
+        shell->RemoveRefreshObserver(this, Flush_Display)) {
+      mObservingRefresh = PR_FALSE;
+    }
   }
 }
 
@@ -241,7 +242,7 @@ nsAccEventQueue::CoalesceEvents()
   switch(tailEvent->mEventRule) {
     case nsAccEvent::eCoalesceFromSameSubtree:
     {
-      for (PRInt32 index = tail - 1; index >= mFlushingEventsCount; index--) {
+      for (PRInt32 index = tail - 1; index >= 0; index--) {
         nsAccEvent* thisEvent = mEvents[index];
 
         if (thisEvent->mEventType != tailEvent->mEventType)
@@ -365,7 +366,7 @@ nsAccEventQueue::CoalesceEvents()
           // Do not emit thisEvent, also apply this result to sibling nodes of
           // thisNode.
           thisEvent->mEventRule = nsAccEvent::eDoNotEmit;
-          ApplyToSiblings(mFlushingEventsCount, index, thisEvent->mEventType,
+          ApplyToSiblings(0, index, thisEvent->mEventType,
                           thisEvent->mNode, nsAccEvent::eDoNotEmit);
           continue;
         }
@@ -386,7 +387,7 @@ nsAccEventQueue::CoalesceEvents()
       // Used for focus event, coalesce more older event since focus event
       // for accessible can be duplicated by event for its document, we are
       // interested in focus event for accessible.
-      for (PRInt32 index = tail - 1; index >= mFlushingEventsCount; index--) {
+      for (PRInt32 index = tail - 1; index >= 0; index--) {
         nsAccEvent* thisEvent = mEvents[index];
         if (thisEvent->mEventType == tailEvent->mEventType &&
             thisEvent->mEventRule == tailEvent->mEventRule &&
@@ -401,7 +402,7 @@ nsAccEventQueue::CoalesceEvents()
     {
       // Check for repeat events, coalesce newly appended event by more older
       // event.
-      for (PRInt32 index = tail - 1; index >= mFlushingEventsCount; index--) {
+      for (PRInt32 index = tail - 1; index >= 0; index--) {
         nsAccEvent* accEvent = mEvents[index];
         if (accEvent->mEventType == tailEvent->mEventType &&
             accEvent->mEventRule == tailEvent->mEventRule &&

accessible/src/base/nsEventShell.h

@@ -45,6 +45,8 @@
 
 #include "nsAutoPtr.h"
 
+#include "nsRefreshDriver.h"
+
 class nsIPersistentProperties;
 
 /**
@@ -90,7 +92,8 @@ private:
 /**
  * Event queue.
  */
-class nsAccEventQueue : public nsISupports
+class nsAccEventQueue : public nsISupports,
+                        public nsARefreshObserver
 {
 public:
   nsAccEventQueue(nsDocAccessible *aDocument);
@@ -120,9 +123,7 @@ private:
    * Process pending events. It calls nsDocAccessible::ProcessPendingEvent()
    * where the real event processing is happen.
    */
-  void Flush();
-
-  NS_DECL_RUNNABLEMETHOD(nsAccEventQueue, Flush)
+  virtual void WillRefresh(mozilla::TimeStamp aTime);
 
   /**
    * Coalesce redundant events from the queue.
@@ -157,9 +158,10 @@ private:
                                          nsAccEvent *aDescendantAccEvent);
 
   /**
-   * Indicates whether events flush is run.
+   * Indicates whether we're waiting on a refresh notification from our
+   * presshell to flush events
    */
-  PRBool mProcessingStarted;
+  PRBool mObservingRefresh;
 
   /**
    * The document accessible reference owning this queue.
@@ -167,13 +169,8 @@ private:
   nsRefPtr<nsDocAccessible> mDocument;
 
   /**
-   * The number of events processed currently. Used to avoid event coalescence
-   * with new events appended to the queue because of events handling.
-   */
-  PRInt32 mFlushingEventsCount;
-
-  /**
-   * Pending events array.
+   * Pending events array.  Don't make this an nsAutoTArray; we use
+   * SwapElements() on it.
    */
   nsTArray<nsRefPtr<nsAccEvent> > mEvents;
 };