Bug 526394. Part 35: Prevent event dispatch and script execution during UpdateViewAfterScroll, even in the presence of malign Win32 reentrant APIs. r=mats

layout/generic/nsGfxScrollFrame.cpp

@@ -1687,7 +1687,21 @@ void nsGfxScrollFrameInner::ScrollVisual(nsIntPoint aPixDelta)
     nearestWidget->Scroll(aPixDelta, blitRects, configurations);
     AdjustViewsAndWidgets(mScrolledFrame, PR_TRUE);
     repaintRegion.MoveBy(-nearestWidgetOffset + offsetToDisplayRoot);
-    vm->UpdateViewAfterScroll(view, repaintRegion);
+
+    {
+      // Block script execution. This suppresses event dispatching in
+      // PresShell::HandleEvent. We need to do this because Windows
+      // is evil and can dispatch WM_MOUSEACTIVATE messages during
+      // our call to ::UpdateWindow (in the presence of out-of-process
+      // plugins, it seems). We are not able to handle event dispatch
+      // here.
+      // No script runners should be added as we paint!
+      nsContentUtils::AddScriptBlockerAndPreventAddingRunners();
+      vm->UpdateViewAfterScroll(view, repaintRegion);
+      nsContentUtils::RemoveScriptBlocker();
+      // Nothing should run here on removing the blocker, since we
+      // prevented the addition of any script runners.
+    }
 
     nsIFrame* presContextRootFrame = presContext->FrameManager()->GetRootFrame();
     if (nearestWidget == presContextRootFrame->GetWindow()) {

view/src/nsViewManager.cpp

@@ -861,25 +861,29 @@ NS_IMETHODIMP nsViewManager::DispatchEvent(nsGUIEvent *aEvent,
 
         // Refresh the view
         if (IsRefreshEnabled()) {
+          nsRefPtr<nsViewManager> rootVM = RootViewManager();
+
           // If an ancestor widget was hidden and then shown, we could
           // have a delayed resize to handle.
           PRBool didResize = PR_FALSE;
-          for (nsViewManager *vm = this; vm;
-               vm = vm->mRootView->GetParent()
-                      ? vm->mRootView->GetParent()->GetViewManager()
-                      : nsnull) {
-            if (vm->mDelayedResize != nsSize(NSCOORD_NONE, NSCOORD_NONE) &&
-                IsViewVisible(vm->mRootView)) {
-              vm->FlushDelayedResize();
+          if (rootVM->mScrollCnt == 0) {
+            for (nsViewManager *vm = this; vm;
+                 vm = vm->mRootView->GetParent()
+                        ? vm->mRootView->GetParent()->GetViewManager()
+                        : nsnull) {
+              if (vm->mDelayedResize != nsSize(NSCOORD_NONE, NSCOORD_NONE) &&
+                  IsViewVisible(vm->mRootView)) {
+                vm->FlushDelayedResize();
 
-              // Paint later.
-              vm->UpdateView(vm->mRootView, NS_VMREFRESH_NO_SYNC);
-              didResize = PR_TRUE;
+                // Paint later.
+                vm->UpdateView(vm->mRootView, NS_VMREFRESH_NO_SYNC);
+                didResize = PR_TRUE;
 
-              // not sure if it's valid for us to claim that we
-              // ignored this, but we're going to do so anyway, since
-              // we didn't actually paint anything
-              *aStatus = nsEventStatus_eIgnore;
+                // not sure if it's valid for us to claim that we
+                // ignored this, but we're going to do so anyway, since
+                // we didn't actually paint anything
+                *aStatus = nsEventStatus_eIgnore;
+              }
             }
           }
 
@@ -888,7 +892,6 @@ NS_IMETHODIMP nsViewManager::DispatchEvent(nsGUIEvent *aEvent,
 
             // Notify view observers that we're about to paint.
             // Make sure to not send WillPaint notifications while scrolling.
-            nsRefPtr<nsViewManager> rootVM = RootViewManager();
 
             nsCOMPtr<nsIWidget> widget;
             rootVM->GetRootWidget(getter_AddRefs(widget));