Bug 775447: Properly count number of touch listeners in AsyncPanZoomController r=cjones

dom/ipc/PBrowser.ipdl

@@ -247,6 +247,8 @@ parent:
                                 nsString aName, nsString aFeatures)
       returns (bool windowOpened);
 
+    NotifyDOMTouchListenerAdded();
+
     __delete__();
 
 child:

dom/ipc/TabChild.cpp

@@ -20,6 +20,7 @@
 #include "mozilla/layers/CompositorChild.h"
 #include "mozilla/layers/PLayersChild.h"
 #include "mozilla/layout/RenderFrameChild.h"
+#include "mozilla/unused.h"
 #include "nsComponentManagerUtils.h"
 #include "nsComponentManagerUtils.h"
 #include "nsContentUtils.h"
@@ -106,6 +107,24 @@ TabChild::TabChild(PRUint32 aChromeFlags, bool aIsBrowserElement,
     printf("creating %d!\n", NS_IsMainThread());
 }
 
+nsresult
+TabChild::Observe(nsISupports *aSubject,
+                  const char *aTopic,
+                  const PRUnichar *aData)
+{
+  if (!strcmp(aTopic, "dom-touch-listener-added")) {
+    nsCOMPtr<nsIDOMWindow> subject(do_QueryInterface(aSubject));
+    nsCOMPtr<nsIDOMWindow> win(do_GetInterface(mWebNav));
+    nsCOMPtr<nsIDOMWindow> topSubject;
+    subject->GetTop(getter_AddRefs(topSubject));
+    if (win == topSubject) {
+      SendNotifyDOMTouchListenerAdded();
+    }
+  }
+
+  return NS_OK;
+}
+
 nsresult
 TabChild::Init()
 {
@@ -121,6 +140,16 @@ TabChild::Init()
 
   nsCOMPtr<nsIDocShellTreeItem> docShellItem(do_QueryInterface(mWebNav));
   docShellItem->SetItemType(nsIDocShellTreeItem::typeContentWrapper);
+
+  nsCOMPtr<nsIObserverService> observerService =
+    do_GetService(NS_OBSERVERSERVICE_CONTRACTID);
+
+  if (observerService) {
+    observerService->AddObserver(this,
+                                 "dom-touch-listener-added",
+                                 false);
+  }
+
   return NS_OK;
 }
 

dom/ipc/TabChild.h

@@ -140,7 +140,8 @@ class TabChild : public PBrowserChild,
                  public nsIWindowProvider,
                  public nsSupportsWeakReference,
                  public nsIDialogCreator,
-                 public nsITabChild
+                 public nsITabChild,
+                 public nsIObserver
 {
     typedef mozilla::layout::RenderFrameChild RenderFrameChild;
     typedef mozilla::dom::ClonedMessageData ClonedMessageData;
@@ -166,6 +167,7 @@ public:
     NS_DECL_NSIWINDOWPROVIDER
     NS_DECL_NSIDIALOGCREATOR
     NS_DECL_NSITABCHILD
+    NS_DECL_NSIOBSERVER
 
     virtual bool RecvLoadURL(const nsCString& uri);
     virtual bool RecvShow(const nsIntSize& size);

dom/ipc/TabParent.cpp

@@ -1090,5 +1090,14 @@ TabParent::RecvBrowserFrameOpenWindow(PBrowserParent* aOpener,
   return true;
 }
 
+bool
+TabParent::RecvNotifyDOMTouchListenerAdded()
+{
+  if (RenderFrameParent* rfp = GetRenderFrame()) {
+    rfp->NotifyDOMTouchListenerAdded();
+  }
+  return true;
+}
+
 } // namespace tabs
 } // namespace mozilla

dom/ipc/TabParent.h

@@ -101,6 +101,7 @@ public:
     virtual bool RecvSetBackgroundColor(const nscolor& aValue);
     virtual bool RecvGetDPI(float* aValue);
     virtual bool RecvGetWidgetNativeData(WindowsHandle* aValue);
+    virtual bool RecvNotifyDOMTouchListenerAdded();
     virtual PContentDialogParent* AllocPContentDialog(const PRUint32& aType,
                                                       const nsCString& aName,
                                                       const nsCString& aFeatures,

gfx/layers/ipc/AsyncPanZoomController.cpp

@@ -53,7 +53,8 @@ AsyncPanZoomController::AsyncPanZoomController(GeckoContentController* aGeckoCon
      mLastSampleTime(TimeStamp::Now()),
      mState(NOTHING),
      mDPI(72),
-     mContentPainterStatus(CONTENT_IDLE)
+     mContentPainterStatus(CONTENT_IDLE),
+     mMayHaveTouchListeners(false)
 {
   if (aGestures == USE_GESTURE_DETECTOR) {
     mGestureEventListener = new GestureEventListener(this);
@@ -784,6 +785,10 @@ void AsyncPanZoomController::NotifyLayersUpdated(const FrameMetrics& aViewportFr
     // we get a larger displayport. This is very bad because we're wasting a
     // paint and not initializating the displayport correctly.
     RequestContentRepaint();
+
+    // Assuming a first paint means a new page has been loaded, clear the flag
+    // indicating that we may have touch listeners.
+    mMayHaveTouchListeners = false;
   } else if (!mFrameMetrics.mContentRect.IsEqualEdges(aViewportFrame.mContentRect)) {
     mFrameMetrics.mCSSContentRect = aViewportFrame.mCSSContentRect;
     SetPageRect(mFrameMetrics.mCSSContentRect);
@@ -802,5 +807,9 @@ void AsyncPanZoomController::UpdateViewportSize(int aWidth, int aHeight) {
   mFrameMetrics = metrics;
 }
 
+void AsyncPanZoomController::NotifyDOMTouchListenerAdded() {
+  mMayHaveTouchListeners = true;
+}
+
 }
 }

gfx/layers/ipc/AsyncPanZoomController.h

@@ -99,6 +99,16 @@ public:
    */
   void UpdateViewportSize(int aWidth, int aHeight);
 
+  /**
+   * A DOM touch listener has been added. When called, we enable the machinery
+   * that allows touch listeners to preventDefault any touch inputs. This should
+   * not be called unless there are actually touch listeners as it introduces
+   * potentially unbounded lag because it causes a round-trip through content.
+   * Usually, if content is responding in a timely fashion, this only introduces
+   * a nearly constant few hundred ms of lag.
+   */
+  void NotifyDOMTouchListenerAdded();
+
   // --------------------------------------------------------------------------
   // These methods must only be called on the compositor thread.
   //
@@ -394,6 +404,10 @@ private:
   // requests a repaint.
   ContentPainterStatus mContentPainterStatus;
 
+  // Whether or not we might have touch listeners. This is a conservative
+  // approximation and may not be accurate.
+  bool mMayHaveTouchListeners;
+
   friend class Axis;
 };
 

layout/ipc/RenderFrameParent.cpp

@@ -852,6 +852,14 @@ RenderFrameParent::BuildDisplayList(nsDisplayListBuilder* aBuilder,
                                  bounds));
 }
 
+void
+RenderFrameParent::NotifyDOMTouchListenerAdded()
+{
+  if (mPanZoomController) {
+    mPanZoomController->NotifyDOMTouchListenerAdded();
+  }
+}
+
 }  // namespace layout
 }  // namespace mozilla
 

layout/ipc/RenderFrameParent.h

@@ -93,6 +93,8 @@ public:
 
   void NotifyDimensionsChanged(int width, int height);
 
+  void NotifyDOMTouchListenerAdded();
+
 protected:
   void ActorDestroy(ActorDestroyReason why) MOZ_OVERRIDE;