Gamepad: honor page visibility

Source/modules/gamepad/NavigatorGamepad.cpp

 /*
  * Copyright (C) 2011, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
  *
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 18 matching lines @@
 #include "RuntimeEnabledFeatures.h"
 #include "core/dom/Document.h"
 #include "core/frame/DOMWindow.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/Navigator.h"
 #include "core/page/Page.h"
 #include "modules/gamepad/GamepadDispatcher.h"
 #include "modules/gamepad/GamepadEvent.h"
 #include "modules/gamepad/GamepadList.h"
 #include "modules/gamepad/WebKitGamepadList.h"
+#include "wtf/TemporaryChange.h"
 
 namespace WebCore {
 
 template<typename T>
 static void sampleGamepad(unsigned index, T& gamepad, const blink::WebGamepad& webGamepad)
 {
     gamepad.setId(webGamepad.id);
     gamepad.setIndex(index);
     gamepad.setConnected(webGamepad.connected);
     gamepad.setTimestamp(webGamepad.timestamp);
@@ skipping 78 matching lines @@
     visitor->trace(m_gamepads);
     visitor->trace(m_webkitGamepads);
     WillBeHeapSupplement<Navigator>::trace(visitor);
 }
 
 void NavigatorGamepad::didConnectOrDisconnectGamepad(unsigned index, const blink::WebGamepad& webGamepad, bool connected)
 {
     ASSERT(index < blink::WebGamepads::itemsLengthCap);
     ASSERT(connected == webGamepad.connected);
 
-    // We should stop listening once we detached.
-    ASSERT(window());
-
     // We register to the dispatcher before sampling gamepads so we need to check if we actually have an event listener.
     if (!m_hasEventListener)
         return;
 
-    if (window()->document()->activeDOMObjectsAreStopped() || window()->document()->activeDOMObjectsAreSuspended())
-        return;
-
     if (!m_gamepads)
         m_gamepads = GamepadList::create();
 
     Gamepad* gamepad = m_gamepads->item(index);
     if (!gamepad)
         gamepad = Gamepad::create();
     sampleGamepad(index, *gamepad, webGamepad);
     m_gamepads->set(index, gamepad);
 
     const AtomicString& eventName = connected ? EventTypeNames::gamepadconnected : EventTypeNames::gamepaddisconnected;
-    RefPtrWillBeRawPtr<GamepadEvent> event = GamepadEvent::create(eventName, false, true, gamepad);
-    window()->dispatchEvent(event);
+    dispatchDeviceEvent(GamepadEvent::create(eventName, false, true, gamepad));
 }
 
 NavigatorGamepad::NavigatorGamepad(LocalFrame* frame)
     : DOMWindowProperty(frame)
     , DeviceSensorEventController(frame ? frame->page() : 0)
     , DOMWindowLifecycleObserver(frame ? frame->domWindow() : 0)
+    , m_canContinueDispatchingSentinelPtr(0)
 {
 }
 
 NavigatorGamepad::~NavigatorGamepad()
 {
 }
 
 const char* NavigatorGamepad::supplementName()
 {
     return "NavigatorGamepad";
 }
 
 void NavigatorGamepad::willDestroyGlobalObjectInFrame()
 {
     stopUpdating();
+    invalidateCanContinueDispatchingSentinel();
     DOMWindowProperty::willDestroyGlobalObjectInFrame();
 }
 
 void NavigatorGamepad::willDetachGlobalObjectFromFrame()
 {
     stopUpdating();
+    invalidateCanContinueDispatchingSentinel();
     DOMWindowProperty::willDetachGlobalObjectFromFrame();
 }
 
 void NavigatorGamepad::registerWithDispatcher()
 {
     GamepadDispatcher::instance().addClient(this);
 }
 
 void NavigatorGamepad::unregisterWithDispatcher()
 {
     GamepadDispatcher::instance().removeClient(this);
 }
 
 bool NavigatorGamepad::hasLastData()
 {
     // Gamepad data is polled instead of pushed.
     return false;
 }
 
 PassRefPtrWillBeRawPtr<Event> NavigatorGamepad::getLastEvent()
 {
     // This is called only when hasLastData() is true.
     ASSERT_NOT_REACHED();
     return nullptr;
 }
 
 bool NavigatorGamepad::isNullEvent(Event*)
 {
-    // This is called only when hasLastData() is true.
-    ASSERT_NOT_REACHED();
     return false;
 }
 
 Document* NavigatorGamepad::document()
 {
     return window() ? window()->document() : 0;
 }
 
 static bool isGamepadEvent(const AtomicString& eventType)
 {
     return eventType == EventTypeNames::gamepadconnected || eventType == EventTypeNames::gamepaddisconnected;
 }
 
 void NavigatorGamepad::didAddEventListener(DOMWindow*, const AtomicString& eventType)
 {
     if (RuntimeEnabledFeatures::gamepadEnabled() && isGamepadEvent(eventType)) {
         if (page() && page()->visibilityState() == PageVisibilityStateVisible)
             startUpdating();
         m_hasEventListener = true;
     }
 }
 
-void NavigatorGamepad::didRemoveEventListener(DOMWindow*, const AtomicString& eventType)
+void NavigatorGamepad::didRemoveEventListener(DOMWindow* window, const AtomicString& eventType)
 {
-    if (isGamepadEvent(eventType))
-        m_hasEventListener = false;
+    if (!isGamepadEvent(eventType) || window->hasEventListeners(EventTypeNames::gamepadconnected) || window->hasEventListeners(EventTypeNames::gamepaddisconnected))
+        return;
+    m_hasEventListener = false;
 }
 
 void NavigatorGamepad::didRemoveAllEventListeners(DOMWindow*)
 {
     m_hasEventListener = false;
 }
 
+void NavigatorGamepad::willBeDestroyed()
+{
+    invalidateCanContinueDispatchingSentinel();
+}
+
+void NavigatorGamepad::pageVisibilityChanged()
+{
+    DeviceSensorEventController::pageVisibilityChanged();
+
+    if (page()->visibilityState() != PageVisibilityStateVisible || !m_hasEventListener)
+        return;
+
+    // Tell the page what has changed. m_gamepads contains the state before we became hidden.
+    // We create a new snapshot and compare them.
+    GamepadList* oldGamepads = m_gamepads.release();
+    gamepads();
+    GamepadList* newGamepads = m_gamepads.get();
+    ASSERT(newGamepads);
+
+    // Set m_gamepads to null so that if we are polled while dispatching it doesn't mess up our snapshot.
+    // After we are done, set it back to the new snapshot otherwise we could report these changes multiple
+    // times after we go hidden and then visible again.
+    WTF::TemporaryChange<PersistentWillBeMember<GamepadList> > padsScope(m_gamepads, nullptr);
+
+    // We need to dispatch multiple events to the page and we have to deal with the fact that we can be destroyed by the event handler.
+    // We use a fancy version of the protecting RefPtr idiom because Supplement's are not RefCounted. Before we die we change the value
+    // of a local variable via our member pointer. After dispatching the event we check this local variable which is safe even if we have died.
+    // TODO(b.kelemen): simplify this when we can rely on Oilpan.
+    bool canContinueDispatchingSentinel = true;
+    WTF::TemporaryChange<bool*> sentinelScope(m_canContinueDispatchingSentinelPtr, &canContinueDispatchingSentinel);
+
+    for (unsigned i = 0; i < blink::WebGamepads::itemsLengthCap; ++i) {
+        Gamepad* oldGamepad = oldGamepads ? oldGamepads->item(i) : 0;
+        Gamepad* newGamepad = newGamepads->item(i);
+        bool oldWasConnected = oldGamepad && oldGamepad->connected();
+        bool newIsConnected = newGamepad && newGamepad->connected();
+        bool connectedGamepadChanged = oldWasConnected && newIsConnected && oldGamepad->id() != newGamepad->id();
+
+        if (connectedGamepadChanged || (oldWasConnected && !newIsConnected)) {
+            const AtomicString& eventName = EventTypeNames::gamepaddisconnected;
+            dispatchDeviceEvent(GamepadEvent::create(eventName, false, true, oldGamepad));
+            if (!canContinueDispatchingSentinel || !m_hasEventListener)
+                return;
+        }
+        if (connectedGamepadChanged || (!oldWasConnected && newIsConnected)) {
+            const AtomicString& eventName = EventTypeNames::gamepadconnected;
+            dispatchDeviceEvent(GamepadEvent::create(eventName, false, true, newGamepad));
+            if (!canContinueDispatchingSentinel || !m_hasEventListener)
+                return;
+        }
+    }
+}
+
+void NavigatorGamepad::invalidateCanContinueDispatchingSentinel()
+{
+    if (m_canContinueDispatchingSentinelPtr)
+        *m_canContinueDispatchingSentinelPtr = false;
+}
+
 } // namespace WebCore