Flush out reflows before processing invalidates and paint events. Fixes a

variety of flicker issues of various sorts, especially when we're not quite
keeping up with the rate of updates in DHTML or in editor.  Bug 244366 and
various dependencies, r+sr=roc

content/events/src/nsEventStateManager.cpp

@@ -471,10 +471,6 @@ nsEventStateManager::PreHandleEvent(nsPresContext* aPresContext,
     GenerateDragGesture(aPresContext, (nsGUIEvent*)aEvent);
     UpdateCursor(aPresContext, aEvent, mCurrentTarget, aStatus);
     GenerateMouseEnterExit(aPresContext, (nsGUIEvent*)aEvent);
-    // Flush reflows and invalidates to eliminate flicker when both a reflow
-    // and visual change occur in an event callback. See bug  #36849
-    // XXXbz eeeew.  Why not fix viewmanager to flush reflows before painting??
-    FlushPendingEvents(aPresContext);
     break;
   case NS_MOUSE_EXIT:
     GenerateMouseEnterExit(aPresContext, (nsGUIEvent*)aEvent);
@@ -1514,10 +1510,11 @@ nsEventStateManager::GenerateDragGesture(nsPresContext* aPresContext,
 
       StopTrackingDragGesture();
     }
-  }
 
-  // Now flush all pending notifications.
-  FlushPendingEvents(aPresContext);
+    // Now flush all pending notifications, for better responsiveness
+    // while dragging.
+    FlushPendingEvents(aPresContext);
+  }
 } // GenerateDragGesture
 
 nsresult
@@ -2838,7 +2835,7 @@ nsEventStateManager::GenerateDragDropEnterExit(nsPresContext* aPresContext,
   //reset mCurretTargetContent to what it was
   mCurrentTargetContent = targetBeforeEvent;
 
-  // Now flush all pending notifications.
+  // Now flush all pending notifications, for better responsiveness.
   FlushPendingEvents(aPresContext);
 }
 
@@ -4429,12 +4426,7 @@ nsEventStateManager::FlushPendingEvents(nsPresContext* aPresContext)
   NS_PRECONDITION(nsnull != aPresContext, "nsnull ptr");
   nsIPresShell *shell = aPresContext->GetPresShell();
   if (shell) {
-    // This is not flushing _Display because of the mess that is bug 36849
-    shell->FlushPendingNotifications(Flush_Layout);
-    nsIViewManager* viewManager = shell->GetViewManager();
-    if (viewManager) {
-      viewManager->FlushPendingInvalidates();
-    }
+    shell->FlushPendingNotifications(Flush_Display);
   }
 }
 

editor/libeditor/base/nsEditor.cpp

@@ -4381,8 +4381,10 @@ nsresult nsEditor::EndUpdateViewBatch()
     {
       PRUint32 updateFlag = NS_VMREFRESH_IMMEDIATE;
 
+      // If we're doing async updates, use NS_VMREFRESH_DEFERRED here, so that
+      // the reflows we caused will get processed before the invalidates.
       if (flags & nsIPlaintextEditor::eEditorUseAsyncUpdatesMask)
-        updateFlag = NS_VMREFRESH_NO_SYNC;
+        updateFlag = NS_VMREFRESH_DEFERRED;
 
       mViewManager->EndUpdateViewBatch(updateFlag);
     }

layout/base/nsPresContext.cpp

@@ -39,6 +39,11 @@
 #include "nsIPresShell.h"
 #include "nsILinkHandler.h"
 #include "nsIDocShellTreeItem.h"
+#include "nsIDocShell.h"
+#include "nsIContentViewer.h"
+#include "nsIDocumentViewer.h"
+#include "nsPIDOMWindow.h"
+#include "nsIFocusController.h"
 #include "nsStyleSet.h"
 #include "nsImageLoader.h"
 #include "nsIContent.h"
@@ -1229,6 +1234,42 @@ nsPresContext::SetPrintSettings(nsIPrintSettings *aPrintSettings)
     mPrintSettings = aPrintSettings;
 }
 
+PRBool
+nsPresContext::EnsureVisible(PRBool aUnsuppressFocus)
+{
+  nsCOMPtr<nsIDocShell> docShell(do_QueryReferent(mContainer));
+  if (docShell) {
+    nsCOMPtr<nsIContentViewer> cv;
+    docShell->GetContentViewer(getter_AddRefs(cv));
+    // Make sure this is the content viewer we belong with
+    nsCOMPtr<nsIDocumentViewer> docV(do_QueryInterface(cv));
+    if (docV) {
+      nsCOMPtr<nsPresContext> currentPresContext;
+      docV->GetPresContext(getter_AddRefs(currentPresContext));
+      if (currentPresContext == this) {
+        // OK, this is us.  We want to call Show() on the content viewer.  But
+        // first, we need to suppress focus changes; otherwise the focus will
+        // get sent to the wrong place (toplevel window).
+        nsCOMPtr<nsPIDOMWindow> privWindow = do_GetInterface(docShell);
+        // XXXbz privWindow should never really be null!
+        nsIFocusController* fc =
+          privWindow ? privWindow->GetRootFocusController() : nsnull;
+        if (fc) {
+          fc->SetSuppressFocus(PR_TRUE,
+                               "nsPresContext::EnsureVisible Suppression");
+        }
+        cv->Show();
+        if (fc && aUnsuppressFocus) {
+          fc->SetSuppressFocus(PR_FALSE,
+                               "nsPresContext::EnsureVisible Suppression");
+        }
+        return PR_TRUE;
+      }
+    }
+  }
+  return PR_FALSE;
+}
+
 nsresult
 NS_NewPresContext(nsPresContext::nsPresContextType aType,
                   nsPresContext** aInstancePtrResult)

layout/base/nsPresContext.h

@@ -587,6 +587,16 @@ public:
   /* Accessor for table of frame properties */
   nsPropertyTable* PropertyTable() { return &mPropertyTable; }
 
+  /* Helper function that ensures that this prescontext is shown in its
+     docshell if it's the most recent prescontext for the docshell.  Returns
+     whether the prescontext is now being shown.
+
+     @param aUnsuppressFocus If this is false, then focus will not be
+     unsuppressed when PR_TRUE is returned.  It's the caller's responsibility
+     to unsuppress focus in that case.
+  */
+  NS_HIDDEN_(PRBool) EnsureVisible(PRBool aUnsuppressFocus);
+  
 #ifdef MOZ_REFLOW_PERF
   NS_HIDDEN_(void) CountReflows(const char * aName,
                                 PRUint32 aType, nsIFrame * aFrame);

layout/base/nsPresShell.cpp

@@ -188,7 +188,6 @@
 
 // Content viewer interfaces
 #include "nsIContentViewer.h"
-#include "nsIDocumentViewer.h"
 
 #ifdef IBMBIDI
 #include "nsIBidiKeyboard.h"
@@ -1222,6 +1221,7 @@ public:
                             nsEventStatus* aStatus);
   NS_IMETHOD ResizeReflow(nsIView *aView, nscoord aWidth, nscoord aHeight);
   NS_IMETHOD_(PRBool) IsVisible();
+  NS_IMETHOD_(void) WillPaint();
 
   // caret handling
   NS_IMETHOD GetCaret(nsICaret **aOutCaret);
@@ -1333,7 +1333,7 @@ protected:
   nsresult AddDummyLayoutRequest(void);
   nsresult RemoveDummyLayoutRequest(void);
 
-  void     WillCauseReflow() {}
+  void     WillCauseReflow() { ++mChangeNestCount; }
   nsresult DidCauseReflow();
   void     DidDoReflow();
   nsresult ProcessReflowCommands(PRBool aInterruptible);
@@ -1393,6 +1393,11 @@ protected:
   PRPackedBool mIgnoreFrameDestruction;
   PRPackedBool mHaveShutDown;
 
+  // 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.
+  PRUint32  mChangeNestCount;
+  
   nsIFrame*   mCurrentEventFrame;
   nsCOMPtr<nsIContent> mCurrentEventContent;
   nsVoidArray mCurrentEventFrameStack;
@@ -4640,38 +4645,11 @@ PresShell::IsPaintingSuppressed(PRBool* aResult)
 void
 PresShell::UnsuppressAndInvalidate()
 {
-  nsCOMPtr<nsPIDOMWindow> ourWindow = do_QueryInterface(mDocument->GetScriptGlobalObject());
-  nsIFocusController *focusController = nsnull;
-  if (ourWindow)
-    focusController = ourWindow->GetRootFocusController();
-  if (focusController)
-    // Suppress focus.  The act of tearing down the old content viewer
-    // causes us to blur incorrectly.
-    focusController->SetSuppressFocus(PR_TRUE, "PresShell suppression on Web page loads");
-
-  nsCOMPtr<nsISupports> container = mPresContext->GetContainer();
-  if (container) {
-    nsCOMPtr<nsIDocShell> cvc(do_QueryInterface(container));
-    if (cvc) {
-      nsCOMPtr<nsIContentViewer> cv;
-      cvc->GetContentViewer(getter_AddRefs(cv));
-      if (cv) {
-        nsCOMPtr<nsIPresShell> kungFuDeathGrip(this);
-        cv->Show();
-        // Calling |Show| may destroy us.  Not sure why yet, but it's
-        // a smoketest blocker.
-        if (mIsDestroying) {
-          if (focusController) {
-            // Unsuppress focus now that we're exiting this code,
-            // otherwise we're stuck in focus suppression, which hoses most of Mozilla
-            focusController->SetSuppressFocus(PR_FALSE, "PresShell suppression on Web page loads");
-          }
-          return;
-        }
-      }
-    }
+  if (!mPresContext->EnsureVisible(PR_FALSE)) {
+    // No point; we're about to be torn down anyway.
+    return;
   }
-
+  
   mPaintingSuppressed = PR_FALSE;
   nsIFrame* rootFrame = FrameManager()->GetRootFrame();
   if (rootFrame) {
@@ -4680,6 +4658,13 @@ PresShell::UnsuppressAndInvalidate()
     rootFrame->Invalidate(rect, PR_FALSE);
   }
 
+  // This makes sure to get the same thing that nsPresContext::EnsureVisible()
+  // got.
+  nsCOMPtr<nsISupports> container = mPresContext->GetContainer();
+  nsCOMPtr<nsPIDOMWindow> ourWindow = do_GetInterface(container);
+  nsIFocusController* focusController =
+    ourWindow ? ourWindow->GetRootFocusController() : nsnull;
+
   if (ourWindow)
     CheckForFocus(ourWindow, focusController, mDocument);
 
@@ -4928,8 +4913,8 @@ PresShell::IsSafeToFlush(PRBool& aIsSafeToFlush)
 {
   aIsSafeToFlush = PR_TRUE;
 
-  if (mIsReflowing) {
-    // Not safe if we are reflowing
+  if (mIsReflowing || mChangeNestCount) {
+    // Not safe if we are reflowing or in the middle of frame construction
     aIsSafeToFlush = PR_FALSE;
   } else {
     // Not safe if we are painting
@@ -5588,7 +5573,7 @@ PresShell::HandleEvent(nsIView         *aView,
   NS_ASSERTION(aView, "null view");
   aHandled = PR_TRUE;
 
-  if (mIsDestroying || mIsReflowing) {
+  if (mIsDestroying || mIsReflowing || mChangeNestCount) {
     return NS_OK;
   }
 
@@ -6018,6 +6003,26 @@ PresShell::IsVisible()
   return res;
 }
 
+NS_IMETHODIMP_(void)
+PresShell::WillPaint()
+{
+  // Don't reenter reflow and don't reflow during frame construction
+  if (mIsReflowing || mChangeNestCount) {
+    return;
+  }
+  
+  // Process reflows, if we have them, to reduce flicker due to invalidates and
+  // reflow being interspersed.  Note that we _do_ allow this to be
+  // interruptible; if we can't do all the reflows it's better to flicker a bit
+  // than to freeze up.
+  // XXXbz this update batch may not be strictly necessary, but it's good form.
+  // XXXbz should we be flushing out style changes here?  Probably not, I'd say.
+  NS_ASSERTION(mViewManager, "Something weird is going on");
+  mViewManager->BeginUpdateViewBatch();
+  ProcessReflowCommands(PR_TRUE);
+  mViewManager->EndUpdateViewBatch(NS_VMREFRESH_NO_SYNC);
+}
+
 nsresult
 PresShell::GetAgentStyleSheets(nsCOMArray<nsIStyleSheet>& aSheets)
 {
@@ -6150,12 +6155,15 @@ PresShell::PostReflowEvent()
 nsresult
 PresShell::DidCauseReflow()
 {
-  // We may have had more reflow commands appended to the queue during
-  // our reflow.  Make sure these get processed at some point.
-  if (!gAsyncReflowDuringDocLoad && mDocumentLoading) {
-    FlushPendingNotifications(Flush_Layout);
-  } else {
-    PostReflowEvent();
+  NS_ASSERTION(mChangeNestCount != 0, "Unexpected call to DidCauseReflow()");
+  if (--mChangeNestCount == 0) {
+    // We may have had more reflow commands appended to the queue during
+    // our reflow.  Make sure these get processed at some point.
+    if (!gAsyncReflowDuringDocLoad && mDocumentLoading) {
+      FlushPendingNotifications(Flush_Layout);
+    } else {
+      PostReflowEvent();
+    }
   }
 
   return NS_OK;

layout/generic/nsObjectFrame.cpp

@@ -104,15 +104,11 @@
 #include "nsIPluginWidget.h"
 #include "nsGUIEvent.h"
 #include "nsIRenderingContext.h"
-#include "nsIContentViewer.h"
-#include "nsIDocumentViewer.h"
-#include "nsIDocShell.h"
 #include "npapi.h"
 #include "nsGfxCIID.h"
 #include "nsUnicharUtils.h"
 #include "nsTransform2D.h"
 #include "nsIImageLoadingContent.h"
-#include "nsIFocusController.h"
 #include "nsPIDOMWindow.h"
 #include "nsContentUtils.h"
 #include "nsIStringBundle.h"
@@ -4104,39 +4100,7 @@ NS_IMETHODIMP nsPluginInstanceOwner::Init(nsPresContext* aPresContext, nsObjectF
   // a page is reloaded. Shutdown happens usually when the last instance
   // is destroyed. Here we make sure the plugin instance in the old
   // document is destroyed before we try to create the new one.
-
-  nsCOMPtr<nsISupports> container = aPresContext->GetContainer();
-  if (container) {
-    // We need to suppress the focus controller so that destroying the old
-    // content viewer doesn't transfer focus to the toplevel window.
-
-    nsCOMPtr<nsPIDOMWindow> privWindow = do_GetInterface(container);
-    nsIFocusController *fc = nsnull;
-    if (privWindow) {
-      fc = privWindow->GetRootFocusController();
-      if (fc)
-        fc->SetSuppressFocus(PR_TRUE, "PluginInstanceOwner::Init Suppression");
-    }
-
-    nsCOMPtr<nsIDocShell> docShell = do_QueryInterface(container);
-    if (docShell) {
-      nsCOMPtr<nsIContentViewer> cv;
-      docShell->GetContentViewer(getter_AddRefs(cv));
-      // Make sure that we're in the presentation that the current
-      // content viewer knows about
-      nsCOMPtr<nsIDocumentViewer> docV(do_QueryInterface(cv));
-      if (docV) {
-        nsCOMPtr<nsPresContext> currentPresContext;
-        docV->GetPresContext(getter_AddRefs(currentPresContext));
-        if (currentPresContext == aPresContext) {
-          cv->Show();
-        }
-      }
-    }
-
-    if (fc)
-      fc->SetSuppressFocus(PR_FALSE, "PluginInstanceOwner::Init Suppression");
-  }
+  aPresContext->EnsureVisible(PR_TRUE);
 
   // register context menu listener
   mCXMenuListener = new nsPluginDOMContextMenuListener();

view/public/nsIViewManager.h

@@ -499,14 +499,6 @@ public:
    */
   NS_IMETHOD IsPainting(PRBool& aIsPainting)=0;
 
-
-  /**
-   * Flush pending invalidates which have been queued up
-   * between DisableRefresh and EnableRefresh calls. 
-   */
-  NS_IMETHOD FlushPendingInvalidates()=0;
-
-
   /**
    * Set the default background color that the view manager should use
    * to paint otherwise unowned areas. If the color isn't known, just set

view/public/nsIViewObserver.h

@@ -91,6 +91,13 @@ public:
    * of having the view trees linked.
    */
   NS_IMETHOD_(PRBool) IsVisible() = 0;
+
+  /**
+   * Notify the observer that we're about to start painting.  This
+   * gives the observer a chance to make some last-minute invalidates
+   * and geometry changes if it wants to.
+   */
+  NS_IMETHOD_(void) WillPaint() = 0;
 };
 
 #endif

view/src/nsView.cpp

@@ -362,10 +362,11 @@ void nsView::SetPositionIgnoringChildWidgets(nscoord aX, nscoord aY)
 void nsView::ResetWidgetBounds(PRBool aRecurse, PRBool aMoveOnly,
                                PRBool aInvalidateChangedSize) {
   if (mWindow) {
-    // If our view manager has refresh disabled, then
-    // do nothing; the view manager will set our position when
-    // refresh is reenabled.
+    // If our view manager has refresh disabled, then do nothing; the view
+    // manager will set our position when refresh is reenabled.  Just let it
+    // know that it has pending updates.
     if (!mViewManager->IsRefreshEnabled()) {
+      mViewManager->PostPendingUpdate();
       return;
     }
 

view/src/nsViewManager.cpp

@@ -62,6 +62,7 @@
 #include "nsInt64.h"
 #include "nsScrollPortView.h"
 #include "nsHashtable.h"
+#include "nsCOMArray.h"
 
 static NS_DEFINE_IID(kBlenderCID, NS_BLENDER_CID);
 static NS_DEFINE_IID(kRegionCID, NS_REGION_CID);
@@ -427,8 +428,7 @@ static PRBool IsViewVisible(nsView *aView)
   // Find out if the root view is visible by asking the view observer
   // (this won't be needed anymore if we link view trees across chrome /
   // content boundaries in DocumentViewerImpl::MakeWindow).
-  nsCOMPtr<nsIViewObserver> vo;
-  aView->GetViewManager()->GetViewObserver(*getter_AddRefs(vo));
+  nsIViewObserver* vo = aView->GetViewManager()->GetViewObserver();
   return vo && vo->IsVisible();
 }
 
@@ -482,7 +482,7 @@ nsViewManager::nsViewManager()
   // assumed to be cleared here.
   mDefaultBackgroundColor = NS_RGBA(0, 0, 0, 0);
   mAllowDoubleBuffering = PR_TRUE; 
-  mHasPendingInvalidates = PR_FALSE;
+  mHasPendingUpdates = PR_FALSE;
   mRecursiveRefreshPending = PR_FALSE;
   mUpdateBatchFlags = 0;
 }
@@ -1696,7 +1696,7 @@ nsViewManager::UpdateWidgetArea(nsView *aWidgetView, const nsRegion &aDamagedReg
     // Don't let dirtyRegion grow beyond 8 rects
     dirtyRegion->SimplifyOutward(8);
     nsViewManager* rootVM = RootViewManager();
-    rootVM->mHasPendingInvalidates = PR_TRUE;
+    rootVM->mHasPendingUpdates = PR_TRUE;
     rootVM->IncrementUpdateCount();
     return;
     // this should only happen at the top level, and this result
@@ -1940,6 +1940,22 @@ NS_IMETHODIMP nsViewManager::DispatchEvent(nsGUIEvent *aEvent, nsEventStatus *aS
             UpdateView(view, NS_VMREFRESH_NO_SYNC);
           } else {
             //NS_ASSERTION(IsViewVisible(view), "painting an invisible view");
+
+            // Just notify our own view observer that we're about to paint
+            // XXXbz do we need to notify other view observers for viewmanagers
+            // in our tree?
+            nsIViewObserver* observer = GetViewObserver();
+            if (observer) {
+              // Do an update view batch, and make sure we don't process those
+              // invalidates right now.  Note that the observer may try to
+              // reenter this code from inside WillPaint() by trying to do a
+              // synchronous paint, but since refresh will be disabled it won't
+              // be able to do the paint.  We should really sort out the rules
+              // on our synch painting api....
+              BeginUpdateViewBatch();
+              observer->WillPaint();
+              EndUpdateViewBatch(NS_VMREFRESH_DEFERRED);
+            }
             Refresh(view, event->renderingContext, region,
                     NS_VMREFRESH_DOUBLE_BUFFER);
           }
@@ -2007,9 +2023,11 @@ NS_IMETHODIMP nsViewManager::DispatchEvent(nsGUIEvent *aEvent, nsEventStatus *aS
 
     case NS_SYSCOLORCHANGED:
       {
+        // Hold a refcount to the observer. The continued existence of the observer will
+        // delay deletion of this view hierarchy should the event want to cause its
+        // destruction in, say, some JavaScript event handler.
         nsView *view = nsView::GetViewFor(aEvent->widget);
-        nsCOMPtr<nsIViewObserver> obs;
-        GetViewObserver(*getter_AddRefs(obs));
+        nsCOMPtr<nsIViewObserver> obs = GetViewObserver();
         if (obs) {
           PRBool handled;
           obs->HandleEvent(view, aEvent, aStatus, PR_TRUE, handled);
@@ -2344,8 +2362,7 @@ nsEventStatus nsViewManager::HandleEvent(nsView* aView, nsGUIEvent* aEvent, PRBo
   // Hold a refcount to the observer. The continued existence of the observer will
   // delay deletion of this view hierarchy should the event want to cause its
   // destruction in, say, some JavaScript event handler.
-  nsCOMPtr<nsIViewObserver> obs;
-  GetViewObserver(*getter_AddRefs(obs));
+  nsCOMPtr<nsIViewObserver> obs = GetViewObserver();
 
   // accessibility events and key events are dispatched directly to the focused view
   if (aEvent->eventStructType == NS_ACCESSIBLE_EVENT
@@ -2361,7 +2378,7 @@ nsEventStatus nsViewManager::HandleEvent(nsView* aView, nsGUIEvent* aEvent, PRBo
   }
     
   nsAutoVoidArray targetViews;
-  nsAutoVoidArray heldRefCountsToOtherVMs;
+  nsCOMArray<nsIViewObserver> heldRefCountsToOtherVMs;
 
   // In fact, we only need to take this expensive path when the event is a mouse event ... riiiight?
   PLArenaPool displayArena;
@@ -2377,10 +2394,9 @@ nsEventStatus nsViewManager::HandleEvent(nsView* aView, nsGUIEvent* aEvent, PRBo
     nsView* v = element->mView;
     nsViewManager* vVM = v->GetViewManager();
     if (vVM != this) {
-      nsIViewObserver* vobs = nsnull;
-      vVM->GetViewObserver(vobs);
-      if (nsnull != vobs) {
-        heldRefCountsToOtherVMs.AppendElement(vobs);
+      nsIViewObserver* vobs = vVM->GetViewObserver();
+      if (vobs) {
+        heldRefCountsToOtherVMs.AppendObject(vobs);
       }
     }
   }
@@ -2406,8 +2422,10 @@ nsEventStatus nsViewManager::HandleEvent(nsView* aView, nsGUIEvent* aEvent, PRBo
           obs->HandleEvent(v, aEvent, &status, i == targetViews.Count() - 1, handled);
         }
       } else {
-        nsCOMPtr<nsIViewObserver> vobs;
-        vVM->GetViewObserver(*getter_AddRefs(vobs));
+        // Hold a refcount to the observer. The continued existence of the observer will
+        // delay deletion of this view hierarchy should the event want to cause its
+        // destruction in, say, some JavaScript event handler.
+        nsCOMPtr<nsIViewObserver> vobs = GetViewObserver();
         if (vobs) {
           vobs->HandleEvent(v, aEvent, &status, i == targetViews.Count() - 1, handled);
         }
@@ -2427,12 +2445,6 @@ nsEventStatus nsViewManager::HandleEvent(nsView* aView, nsGUIEvent* aEvent, PRBo
   PL_FreeArenaPool(&displayArena);
   PL_FinishArenaPool(&displayArena);
 
-  // release death grips
-  for (i = 0; i < heldRefCountsToOtherVMs.Count(); i++) {
-    nsIViewObserver* element = NS_STATIC_CAST(nsIViewObserver*, heldRefCountsToOtherVMs.ElementAt(i));
-    NS_RELEASE(element);
-  }  
-
   return status;
 }
 
@@ -3294,14 +3306,12 @@ NS_IMETHODIMP nsViewManager::EnableRefresh(PRUint32 aUpdateFlags)
   // nested batching can combine IMMEDIATE with DEFERRED. Favour
   // IMMEDIATE over DEFERRED and DEFERRED over NO_SYNC.
   if (aUpdateFlags & NS_VMREFRESH_IMMEDIATE) {
-    ProcessPendingUpdates(mRootView);
-    mHasPendingInvalidates = PR_FALSE;
+    FlushPendingInvalidates();
     Composite();
   } else if (aUpdateFlags & NS_VMREFRESH_DEFERRED) {
     PostInvalidateEvent();
   } else { // NO_SYNC
-    ProcessPendingUpdates(mRootView);
-    mHasPendingInvalidates = PR_FALSE;
+    FlushPendingInvalidates();
   }
 
   return NS_OK;
@@ -4146,18 +4156,53 @@ nsViewManager::IsPainting(PRBool& aIsPainting)
   return NS_OK;
 }
 
-NS_IMETHODIMP
+void
 nsViewManager::FlushPendingInvalidates()
 {
-  if (!IsRootVM()) {
-    return RootViewManager()->FlushPendingInvalidates();
-  }
+  NS_ASSERTION(IsRootVM(), "Must be root VM for this to be called!\n");
+  NS_ASSERTION(mUpdateBatchCnt == 0, "Must not be in an update batch!");
+  // XXXbz this is probably not quite OK yet, if callers can explicitly
+  // DisableRefresh while we have an event posted.
+  // NS_ASSERTION(mRefreshEnabled, "How did we get here?");
+
+  // Let all the view observers of all viewmanagers in this tree know that
+  // we're about to "paint" (this lets them get in their invalidates now so
+  // we don't go through two invalidate-processing cycles).
+  NS_ASSERTION(gViewManagers, "Better have a viewmanagers array!");
+
+  // Disable refresh while we notify our view observers, so that if they do
+  // vie w update batches we don't reenter this code and so that we batch
+  // all of them together.  We don't use
+  // BeginUpdateViewBatch/EndUpdateViewBatch, since that would reenter this
+  // exact code, but we want the effect of a single big update batch.
+  PRBool refreshEnabled = mRefreshEnabled;
+  mRefreshEnabled = PR_FALSE;
+  ++mUpdateBatchCnt;
   
-  if (mHasPendingInvalidates) {
-    ProcessPendingUpdates(mRootView);
-    mHasPendingInvalidates = PR_FALSE;
+  PRInt32 index;
+  for (index = 0; index < mVMCount; index++) {
+    nsViewManager* vm = (nsViewManager*)gViewManagers->ElementAt(index);
+    if (vm->RootViewManager() == this) {
+      // One of our kids
+      nsIViewObserver* observer = vm->GetViewObserver();
+      if (observer) {
+        observer->WillPaint();
+        NS_ASSERTION(mUpdateBatchCnt == 1, "Observer did not end view batch?");
+      }
+    }
+  }
+
+  --mUpdateBatchCnt;
+  // Someone could have called EnableRefresh on us from inside WillPaint().
+  // Only reset the old mRefreshEnabled value if the current value is false.
+  if (!mRefreshEnabled) {
+    mRefreshEnabled = refreshEnabled;
+  }
+
+  if (mHasPendingUpdates) {
+    ProcessPendingUpdates(mRootView);
+    mHasPendingUpdates = PR_FALSE;
   }
-  return NS_OK;
 }
 
 void

view/src/nsViewManager.h

@@ -240,7 +240,6 @@ public:
  
   NS_IMETHOD AllowDoubleBuffering(PRBool aDoubleBuffer);
   NS_IMETHOD IsPainting(PRBool& aIsPainting);
-  NS_IMETHOD FlushPendingInvalidates();
   NS_IMETHOD SetDefaultBackgroundColor(nscolor aColor);
   NS_IMETHOD GetDefaultBackgroundColor(nscolor* aColor);
   NS_IMETHOD GetLastUserEventTime(PRUint32& aTime);
@@ -268,9 +267,10 @@ public:
 
 protected:
   virtual ~nsViewManager();
-  void ProcessPendingUpdates(nsView *aView);
 
 private:
+  void FlushPendingInvalidates();
+  void ProcessPendingUpdates(nsView *aView);
   void ReparentChildWidgets(nsIView* aView, nsIWidget *aNewWidget);
   void ReparentWidgets(nsIView* aView, nsIView *aParent);
   already_AddRefed<nsIRenderingContext> CreateRenderingContext(nsView &aView);
@@ -471,6 +471,11 @@ public: // NOT in nsIViewManager, so private to the view module
 
   PRBool IsRefreshEnabled() { return RootViewManager()->mRefreshEnabled; }
 
+  nsIViewObserver* GetViewObserver() { return mObserver; }
+
+  // Call this when you need to let the viewmanager know that it now has
+  // pending updates.
+  void PostPendingUpdate() { RootViewManager()->mHasPendingUpdates = PR_TRUE; }
 private:
   nsIDeviceContext  *mContext;
   float             mTwipsToPixels;
@@ -512,7 +517,7 @@ private:
   // Use IsPainting() and SetPainting() to access mPainting.
   PRPackedBool      mPainting;
   PRPackedBool      mRecursiveRefreshPending;
-  PRPackedBool      mHasPendingInvalidates;
+  PRPackedBool      mHasPendingUpdates;
 
   //from here to public should be static and locked... MMP
   static PRInt32           mVMCount;        //number of viewmanagers