Bug 1305458 Part2: Add nsIDOMEventTarget::PreHandleEvent. r=smaug

MozReview-Commit-ID: HiCDTXgNr0l

--HG--
extra : rebase_source : ce3318fac96a1baf86059274230b1e6cae750347

dom/events/EventDispatcher.cpp

@@ -136,6 +136,7 @@ static bool IsEventTargetChrome(EventTarget* aEventTarget,
 #define NS_TARGET_CHAIN_MAY_HAVE_MANAGER        (1 << 2)
 #define NS_TARGET_CHAIN_CHECKED_IF_CHROME       (1 << 3)
 #define NS_TARGET_CHAIN_IS_CHROME_CONTENT       (1 << 4)
+#define NS_TARGET_CHAIN_WANTS_PRE_HANDLE_EVENT  (1 << 5)
 
 // EventTargetChainItem represents a single item in the event target chain.
 class EventTargetChainItem
@@ -209,6 +210,20 @@ public:
     return !!(mFlags & NS_TARGET_CHAIN_WANTS_WILL_HANDLE_EVENT);
   }
 
+  void SetWantsPreHandleEvent(bool aWants)
+  {
+    if (aWants) {
+      mFlags |= NS_TARGET_CHAIN_WANTS_PRE_HANDLE_EVENT;
+    } else {
+      mFlags &= ~NS_TARGET_CHAIN_WANTS_PRE_HANDLE_EVENT;
+    }
+  }
+
+  bool WantsPreHandleEvent()
+  {
+    return !!(mFlags & NS_TARGET_CHAIN_WANTS_PRE_HANDLE_EVENT);
+  }
+
   void SetMayHaveListenerManager(bool aMayHave)
   {
     if (aMayHave) {
@@ -245,6 +260,11 @@ public:
    */
   void GetEventTargetParent(EventChainPreVisitor& aVisitor);
 
+  /**
+   * Calls PreHandleEvent for those items which called SetWantsPreHandleEvent.
+   */
+  void PreHandleEvent(EventChainVisitor& aVisitor);
+
   /**
    * If the current item in the event target chain has an event listener
    * manager, this method calls EventListenerManager::HandleEvent().
@@ -324,10 +344,20 @@ EventTargetChainItem::GetEventTargetParent(EventChainPreVisitor& aVisitor)
   SetForceContentDispatch(aVisitor.mForceContentDispatch);
   SetWantsWillHandleEvent(aVisitor.mWantsWillHandleEvent);
   SetMayHaveListenerManager(aVisitor.mMayHaveListenerManager);
+  SetWantsPreHandleEvent(aVisitor.mWantsPreHandleEvent);
   mItemFlags = aVisitor.mItemFlags;
   mItemData = aVisitor.mItemData;
 }
 
+void
+EventTargetChainItem::PreHandleEvent(EventChainVisitor& aVisitor)
+{
+  if (!WantsPreHandleEvent()) {
+    return;
+  }
+  Unused << mTarget->PreHandleEvent(aVisitor);
+}
+
 void
 EventTargetChainItem::PostHandleEvent(EventChainPostVisitor& aVisitor)
 {
@@ -706,7 +736,11 @@ EventDispatcher::Dispatch(nsISupports* aTarget,
           targets[i] = chain[i].CurrentTarget()->GetTargetForDOMEvent();
         }
       } else {
-        // Event target chain is created. Handle the chain.
+        // Event target chain is created. PreHandle the chain.
+        for (uint32_t i = 0; i < chain.Length(); ++i) {
+          chain[i].PreHandleEvent(preVisitor);
+        }
+        // Handle the chain.
         EventChainPostVisitor postVisitor(preVisitor);
         EventTargetChainItem::HandleEventTargetChain(chain, postVisitor,
                                                      aCallback, cd);

dom/events/EventDispatcher.h

@@ -123,6 +123,7 @@ public:
     , mOriginalTargetIsInAnon(aIsInAnon)
     , mWantsWillHandleEvent(false)
     , mMayHaveListenerManager(true)
+    , mWantsPreHandleEvent(false)
     , mParentTarget(nullptr)
     , mEventTargetAtParent(nullptr)
   {
@@ -137,6 +138,7 @@ public:
     mForceContentDispatch = false;
     mWantsWillHandleEvent = false;
     mMayHaveListenerManager = true;
+    mWantsPreHandleEvent = false;
     mParentTarget = nullptr;
     mEventTargetAtParent = nullptr;
   }
@@ -186,6 +188,12 @@ public:
    */
   bool                  mMayHaveListenerManager;
 
+  /**
+   * Whether or not nsIDOMEventTarget::PreHandleEvent will be called. Default is
+   * false;
+   */
+  bool mWantsPreHandleEvent;
+
   /**
    * Parent item in the event target chain.
    */

dom/interfaces/events/nsIDOMEventTarget.idl

@@ -13,6 +13,7 @@
 using mozilla::dom::Nullable;
 
 namespace mozilla {
+class EventChainVisitor;
 class EventChainPostVisitor;
 class EventChainPreVisitor;
 class EventListenerManager;
@@ -226,6 +227,18 @@ interface nsIDOMEventTarget : nsISupports
   [noscript, nostdcall]
   void GetEventTargetParent(in EventChainPreVisitorRef aVisitor);
 
+  /**
+   * Called before the capture phase of the event flow and after event target
+   * chain creation. This is used to handle those stuffs must be executed before
+   * dispatch event to DOM
+   */
+%{C++
+  virtual nsresult PreHandleEvent(mozilla::EventChainVisitor& aVisitor)
+  {
+    return NS_OK;
+  }
+%}
+
   /**
    * If EventChainPreVisitor.mWantsWillHandleEvent is set PR_TRUE,
    * called just before possible event handlers on this object will be called.