Bug 455988. Optimize MozAfterPaint so we never even dispatch an XPCOM event if there are no listeners. r=smaug,sr=mats

content/base/src/nsNodeUtils.cpp

@@ -590,6 +590,9 @@ nsNodeUtils::CloneAndAdopt(nsINode *aNode, PRBool aClone, PRBool aDeep,
         aNode->GetListenerManager(PR_FALSE, getter_AddRefs(elm));
         if (elm) {
           window->SetMutationListeners(elm->MutationListenerBits());
+          if (elm->MayHavePaintEventListener()) {
+            window->SetHasPaintEventListeners();
+          }
         }
       }
     }

content/events/public/nsIEventListenerManager.h

@@ -38,7 +38,7 @@
 #ifndef nsIEventListenerManager_h__
 #define nsIEventListenerManager_h__
 
-#include "nsEvent.h"
+#include "nsGUIEvent.h"
 #include "nsISupports.h"
 
 class nsPresContext;
@@ -53,15 +53,19 @@ class nsPIDOMEventTarget;
  * Event listener manager interface.
  */
 #define NS_IEVENTLISTENERMANAGER_IID \
-{ 0x0cdf1660, 0x3ac1, 0x4b84, \
-  { 0xa9, 0x35, 0xc0, 0xc0, 0xe5, 0x5d, 0x73, 0xca } }
-
+{ 0xadfdc265, 0xea1c, 0x4c0b, \
+  { 0x91, 0xca, 0x37, 0x67, 0x2c, 0x83, 0x92, 0x1f } }
 
 class nsIEventListenerManager : public nsISupports {
 
 public:
   NS_DECLARE_STATIC_IID_ACCESSOR(NS_IEVENTLISTENERMANAGER_IID)
 
+  nsIEventListenerManager() : mMayHavePaintEventListener(PR_FALSE),
+    mMayHaveMutationListeners(PR_FALSE),
+    mNoListenerForEvent(NS_EVENT_TYPE_NULL)
+  {}
+
   /**
   * Sets events listeners of all types.
   * @param an event listener
@@ -194,6 +198,21 @@ public:
    * Returns PR_TRUE if there is at least one event listener.
    */
   virtual PRBool HasListeners() = 0;
+
+
+  /**
+   * Returns PR_TRUE if there may be a paint event listener registered,
+   * PR_FALSE if there definitely isn't.
+   */
+  PRBool MayHavePaintEventListener() { return mMayHavePaintEventListener; }
+
+protected:
+  PRUint32 mMayHavePaintEventListener : 1;
+  PRUint32 mMayHaveMutationListeners : 1;
+  // These two member variables are used to cache the information
+  // about the last event which was handled but for which event listener manager
+  // didn't have event listeners.
+  PRUint32 mNoListenerForEvent : 30;
 };
 
 NS_DEFINE_STATIC_IID_ACCESSOR(nsIEventListenerManager,

content/events/src/nsEventListenerManager.cpp

@@ -342,9 +342,7 @@ PRUint32 nsEventListenerManager::mInstanceCount = 0;
 PRUint32 nsEventListenerManager::sCreatedCount = 0;
 
 nsEventListenerManager::nsEventListenerManager() :
-  mTarget(nsnull),
-  mMayHaveMutationListeners(PR_FALSE),
-  mNoListenerForEvent(NS_EVENT_TYPE_NULL)
+  mTarget(nsnull)
 {
   ++mInstanceCount;
   ++sCreatedCount;
@@ -430,6 +428,27 @@ nsEventListenerManager::GetTypeDataForEventName(nsIAtom* aName)
   return nsnull;
 }
 
+nsPIDOMWindow*
+nsEventListenerManager::GetInnerWindowForTarget()
+{
+  nsCOMPtr<nsINode> node = do_QueryInterface(mTarget);
+  if (node) {
+    // XXX sXBL/XBL2 issue -- do we really want the owner here?  What
+    // if that's the XBL document?
+    nsIDocument* document = node->GetOwnerDoc();
+    if (document)
+      return document->GetInnerWindow();
+  }
+
+  nsCOMPtr<nsPIDOMWindow> window = do_QueryInterface(mTarget);
+  if (window) {
+    NS_ASSERTION(window->IsInnerWindow(), "Target should not be an outer window");
+    return window;
+  }
+
+  return nsnull;
+}
+
 nsresult
 nsEventListenerManager::AddEventListener(nsIDOMEventListener *aListener,
                                          PRUint32 aType,
@@ -497,29 +516,19 @@ nsEventListenerManager::AddEventListener(nsIDOMEventListener *aListener,
   ls->mHandlerIsString = PR_FALSE;
   ls->mTypeData = aTypeData;
 
-  // For mutation listeners, we need to update the global bit on the DOM window.
-  // Otherwise we won't actually fire the mutation event.
-  if (aType >= NS_MUTATION_START && aType <= NS_MUTATION_END) {
+  if (aType == NS_AFTERPAINT) {
+    mMayHavePaintEventListener = PR_TRUE;
+    nsPIDOMWindow* window = GetInnerWindowForTarget();
+    if (window) {
+      window->SetHasPaintEventListener();
+    }
+  } else if (aType >= NS_MUTATION_START && aType <= NS_MUTATION_END) {
+    // For mutation listeners, we need to update the global bit on the DOM window.
+    // Otherwise we won't actually fire the mutation event.
     mMayHaveMutationListeners = PR_TRUE;
     // Go from our target to the nearest enclosing DOM window.
-    nsCOMPtr<nsPIDOMWindow> window;
-    nsCOMPtr<nsIDocument> document;
-    nsCOMPtr<nsINode> node(do_QueryInterface(mTarget));
-    if (node) {
-      // XXX sXBL/XBL2 issue -- do we really want the owner here?  What
-      // if that's the XBL document?
-      document = node->GetOwnerDoc();
-      if (document) {
-        window = document->GetInnerWindow();
-      }
-    }
-
-    if (!window) {
-      window = do_QueryInterface(mTarget);
-    }
+    nsPIDOMWindow* window = GetInnerWindowForTarget();
     if (window) {
-      NS_ASSERTION(window->IsInnerWindow(),
-                   "Setting mutation listener bits on outer window?");
       // If aType is NS_MUTATION_SUBTREEMODIFIED, we need to listen all
       // mutations. nsContentUtils::HasMutationListeners relies on this.
       window->SetMutationListeners((aType == NS_MUTATION_SUBTREEMODIFIED) ?

content/events/src/nsEventListenerManager.h

@@ -191,14 +191,10 @@ protected:
                          nsIPresShell *aPresShell, nsPoint& aTargetPt);
   nsresult GetDOM2EventGroup(nsIDOMEventGroup** aGroup);
   PRBool ListenerCanHandle(nsListenerStruct* aLs, nsEvent* aEvent);
+  nsPIDOMWindow* GetInnerWindowForTarget();
 
   nsAutoTObserverArray<nsListenerStruct, 2> mListeners;
   nsISupports*                              mTarget;  //WEAK
-  PRUint32                                  mMayHaveMutationListeners : 1;
-  // These two member variables are used to cache the information
-  // about the last event which was handled but for which event listener manager
-  // didn't have event listeners.
-  PRUint32                                  mNoListenerForEvent : 31;
   nsCOMPtr<nsIAtom>                         mNoListenerForEventAtom;
 
   static PRUint32                           mInstanceCount;

dom/public/base/nsPIDOMWindow.h

@@ -76,8 +76,8 @@ class nsScriptObjectHolder;
 class nsXBLPrototypeHandler;
 
 #define NS_PIDOMWINDOW_IID \
-{ 0x909852b5, 0xb9e6, 0x4d94, \
-  { 0x8d, 0xe3, 0x05, 0x16, 0x34, 0x80, 0x0b, 0x73 } }
+{ 0x3d2b6b38, 0x810d, 0x4ac5, \
+  { 0x81, 0x7c, 0xb9, 0x70, 0x81, 0x80, 0x4d, 0x9f } }
 
 class nsPIDOMWindow : public nsIDOMWindowInternal
 {
@@ -379,6 +379,24 @@ public:
     return mIsModalContentWindow;
   }
 
+  /**
+   * Call this to indicate that some node (this window, its document,
+   * or content in that document) has a paint event listener.
+   */
+  void SetHasPaintEventListeners()
+  {
+    mMayHavePaintEventListener = PR_TRUE;
+  }
+
+  /**
+   * Call this to check whether some node (this window, its document,
+   * or content in that document) has a paint event listener.
+   */
+  PRBool HasPaintEventListeners()
+  {
+    return mMayHavePaintEventListener;
+  }
+  
   /**
    * Initialize window.java and window.Packages, and start LiveConnect
    * if we're running with a non-NPRuntime enabled Java plugin.
@@ -398,6 +416,7 @@ protected:
     : mFrameElement(nsnull), mDocShell(nsnull), mModalStateDepth(0),
       mRunningTimeout(nsnull), mMutationBits(0), mIsDocumentLoaded(PR_FALSE),
       mIsHandlingResizeEvent(PR_FALSE), mIsInnerWindow(aOuterWindow != nsnull),
+      mMayHavePaintEventListener(PR_FALSE),
       mIsModalContentWindow(PR_FALSE), mInnerWindow(nsnull),
       mOuterWindow(aOuterWindow)
   {
@@ -427,6 +446,7 @@ protected:
   PRPackedBool           mIsDocumentLoaded;
   PRPackedBool           mIsHandlingResizeEvent;
   PRPackedBool           mIsInnerWindow;
+  PRPackedBool           mMayHavePaintEventListener;
 
   // This variable is used on both inner and outer windows (and they
   // should match).

layout/base/nsPresContext.cpp

@@ -84,6 +84,7 @@
 #include "nsRuleNode.h"
 #include "nsEventDispatcher.h"
 #include "gfxUserFontSet.h"
+#include "nsIEventListenerManager.h"
 
 #ifdef IBMBIDI
 #include "nsBidiPresUtils.h"
@@ -1541,10 +1542,10 @@ nsPresContext::SetUserFontSet(gfxUserFontSet *aUserFontSet)
 void
 nsPresContext::FireDOMPaintEvent()
 {
-  nsCOMPtr<nsIDocShell> docShell(do_QueryReferent(mContainer));
-  if (!docShell)
+  nsCOMPtr<nsPIDOMWindow> ourWindow = mDocument->GetWindow();
+  if (!ourWindow)
     return;
-  nsCOMPtr<nsPIDOMWindow> ourWindow = do_GetInterface(docShell);
+
   nsISupports* eventTarget = ourWindow;
   if (mSameDocDirtyRegion.IsEmpty() && !IsChrome()) {
     // Don't tell the window about this event, it should not know that
@@ -1570,10 +1571,43 @@ nsPresContext::FireDOMPaintEvent()
   nsEventDispatcher::Dispatch(eventTarget, this, &event);
 }
 
+static PRBool MayHavePaintEventListener(nsPIDOMWindow* aInnerWindow)
+{
+  if (!aInnerWindow)
+    return PR_FALSE;
+  if (aInnerWindow->HasPaintEventListeners())
+    return PR_TRUE;
+
+  nsPIDOMEventTarget* chromeEventHandler = aInnerWindow->GetChromeEventHandler();
+  if (!chromeEventHandler)
+    return PR_FALSE;
+
+  nsCOMPtr<nsIEventListenerManager> manager;
+  chromeEventHandler->GetListenerManager(PR_FALSE, getter_AddRefs(manager));
+  if (manager && manager->MayHavePaintEventListener())
+    return PR_TRUE;
+
+  nsCOMPtr<nsINode> node = do_QueryInterface(chromeEventHandler);
+  if (node)
+    return MayHavePaintEventListener(node->GetOwnerDoc()->GetInnerWindow());
+
+  nsCOMPtr<nsPIDOMWindow> window = do_QueryInterface(chromeEventHandler);
+  if (window)
+    return MayHavePaintEventListener(window);
+
+  return PR_FALSE;
+}
+
 void
 nsPresContext::NotifyInvalidation(const nsRect& aRect, PRBool aIsCrossDoc)
 {
-  if (aRect.IsEmpty())
+  // If there is no paint event listener, then we don't need to fire
+  // the asynchronous event. We don't even need to record invalidation.
+  // MayHavePaintEventListener is pretty cheap and we could make it
+  // even cheaper by providing a more efficient
+  // nsPIDOMWindow::GetListenerManager.
+  if (aRect.IsEmpty() ||
+      !MayHavePaintEventListener(mDocument->GetInnerWindow()))
     return;
 
   if (mSameDocDirtyRegion.IsEmpty() && mCrossDocDirtyRegion.IsEmpty()) {