ScreenOrientationController: task-based dispatching of change events.

Source/modules/screen_orientation/ScreenOrientationController.cpp

 // Copyright 2014 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 "config.h"
 #include "modules/screen_orientation/ScreenOrientationController.h"
 
+#include "core/dom/Document.h"
+#include "core/dom/ExecutionContextTask.h"
 #include "core/events/Event.h"
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/page/Page.h"
 #include "modules/screen_orientation/ScreenOrientation.h"
 #include "modules/screen_orientation/ScreenOrientationDispatcher.h"
 #include "platform/LayoutTestSupport.h"
 #include "platform/PlatformScreen.h"
 #include "public/platform/WebScreenOrientationClient.h"
 
@@ skipping 13 matching lines @@
 
 ScreenOrientationController* ScreenOrientationController::from(LocalFrame& frame)
 {
     return static_cast<ScreenOrientationController*>(WillBeHeapSupplement<LocalFrame>::from(frame, supplementName()));
 }
 
 ScreenOrientationController::ScreenOrientationController(LocalFrame& frame, WebScreenOrientationClient* client)
     : LocalFrameLifecycleObserver(&frame)
     , PlatformEventController(frame.page())
     , m_client(client)
-    , m_dispatchEventTimer(this, &ScreenOrientationController::dispatchEventTimerFired)
+    , m_isDispatchingEvent(false)
 {
 }
 
 const char* ScreenOrientationController::supplementName()
 {
     return "ScreenOrientationController";
 }
 
 // Compute the screen orientation using the orientation angle and the screen width / height.
 WebScreenOrientationType ScreenOrientationController::computeOrientation(FrameView* view)
@@ skipping 76 matching lines @@
     // Keep track of the frames that need to be notified before notifying the
     // current frame as it will prevent side effects from the change event
     // handlers.
     WillBeHeapVector<RefPtrWillBeMember<LocalFrame>> childFrames;
     for (Frame* child = frame()->tree().firstChild(); child; child = child->tree().nextSibling()) {
         if (child->isLocalFrame())
             childFrames.append(toLocalFrame(child));
     }
 
     // Notify current orientation object.
-    if (!m_dispatchEventTimer.isActive())
-        m_dispatchEventTimer.startOneShot(0, FROM_HERE);
+    if (!m_isDispatchingEvent) {
+        if (Document* document = frame()->document()) {
+            document->postTask(FROM_HERE, createSameThreadTask(&ScreenOrientationController::dispatchChangeEvent, this));

[alex clarke (OOO till 29th), 2015/04/15 09:27:32]

FYI the blink scheduler team are thinking of adding a helper to make this kind
of refactor easier.

Something on the lines of helper.postUniqueTask(FROM_HERE,
createSameThreadTask(&ScreenOrientationController::dispatchChangeEvent, this));

The helper would contain the m_isDispatchingEvent logic (since this seems to be
a reasonably common pattern).

The helper's constructor would take the WebThread you wanted the task to run on.

When we implement that, we'll probably refactor this to use the new method. 

+            m_isDispatchingEvent = true;
+        }
+    }
 
     // ... and child frames, if they have a ScreenOrientationController.
     for (size_t i = 0; i < childFrames.size(); ++i) {
         if (ScreenOrientationController* controller = ScreenOrientationController::from(*childFrames[i]))
             controller->notifyOrientationChanged();
     }
 }
 
 void ScreenOrientationController::setOrientation(ScreenOrientation* orientation)
 {
@@ skipping 12 matching lines @@
 }
 
 void ScreenOrientationController::unlock()
 {
     // When detached, the client is no longer valid.
     if (!m_client)
         return;
     m_client->unlockOrientation();
 }
 
-void ScreenOrientationController::dispatchEventTimerFired(Timer<ScreenOrientationController>*)
+void ScreenOrientationController::dispatchChangeEvent()
 {
+    m_isDispatchingEvent = false;
     if (!m_orientation)
         return;
     m_orientation->dispatchEvent(Event::create(EventTypeNames::change));
 }
 
 void ScreenOrientationController::didUpdateData()
 {
     // Do nothing.
 }
 
@@ skipping 27 matching lines @@
 
 DEFINE_TRACE(ScreenOrientationController)
 {
     visitor->trace(m_orientation);
     LocalFrameLifecycleObserver::trace(visitor);
     WillBeHeapSupplement<LocalFrame>::trace(visitor);
     PlatformEventController::trace(visitor);
 }
 
 } // namespace blink