Introduce EventProcessor::OnEventProcessingStarted()

ui/events/event_processor.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/events/event_processor.h"
 
 #include "ui/events/event_target.h"
 #include "ui/events/event_targeter.h"
 
 namespace ui {
 
 EventDispatchDetails EventProcessor::OnEventFromSource(Event* event) {
   EventTarget* root = GetRootTarget();
   CHECK(root);
   EventTargeter* targeter = root->GetEventTargeter();
   CHECK(targeter);
-  PrepareEventForDispatch(event);
 
   // If |event| is in the process of being dispatched or has already been
   // dispatched, then dispatch a copy of the event instead.
   bool dispatch_original_event = event->phase() == EP_PREDISPATCH;
   Event* event_to_dispatch = event;
   scoped_ptr<Event> event_copy;
   if (!dispatch_original_event) {
     event_copy = Event::Clone(*event);
     event_to_dispatch = event_copy.get();
   }
 
-  EventTarget* target = targeter->FindTargetForEvent(root, event_to_dispatch);
+  OnEventProcessingStarted(event_to_dispatch);
+  EventTarget* target = NULL;
+  if (!event_to_dispatch->handled())
+    target = targeter->FindTargetForEvent(root, event_to_dispatch);

[tdanderson, 2014/09/23 21:30:27]

Another option would be to have EventTargeter::FindTargetForEvent() and all of
its overrides just do an early return NULL if the event is handled, then we
could remove the check at line 30. But I think if you prefer that option, it
should be done in a separate CL.

[sadrul, 2014/09/25 16:12:00]

I think we should do this here, and not require all targeters to have to look at
the event's dispatch state.

[tdanderson, 2014/09/25 17:11:58]

Sounds good, left as-is then.

+
   EventDispatchDetails details;
   while (target) {
     details = DispatchEvent(target, event_to_dispatch);
 
     if (!dispatch_original_event) {
       if (event_to_dispatch->stopped_propagation())
         event->StopPropagation();
       else if (event_to_dispatch->handled())
         event->SetHandled();
     }
 
     if (details.dispatcher_destroyed)
       return details;
 
     if (details.target_destroyed || event->handled())
       break;
 
     target = targeter->FindNextBestTarget(target, event_to_dispatch);
   }
 
   OnEventProcessingFinished(event);
   return details;
 }
 
-void EventProcessor::PrepareEventForDispatch(Event* event) {
+void EventProcessor::OnEventProcessingStarted(Event* event) {
 }
 
 void EventProcessor::OnEventProcessingFinished(Event* event) {
 }
 
 }  // namespace ui