Gamepad: make gamepad events play well with 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 108 matching lines @@
         startUpdating();
         sampleGamepads<Gamepad>(m_gamepads.get());
     }
     return m_gamepads.get();
 }
 
 void NavigatorGamepad::trace(Visitor* visitor)
 {
     visitor->trace(m_gamepads);
     visitor->trace(m_webkitGamepads);
+    visitor->trace(m_pendingEvents);
     WillBeHeapSupplement<Navigator>::trace(visitor);
 }
 
 void NavigatorGamepad::didUpdateData()
 {
     // 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;
 
     const GamepadDispatcher::ConnectionChange& change = GamepadDispatcher::instance().latestConnectionChange();
 
     if (!m_gamepads)
         m_gamepads = GamepadList::create();
 
     Gamepad* gamepad = m_gamepads->item(change.index);
     if (!gamepad)
         gamepad = Gamepad::create();
     sampleGamepad(change.index, *gamepad, change.pad);
     m_gamepads->set(change.index, gamepad);
 
-    const AtomicString& eventName = change.pad.connected ? EventTypeNames::gamepadconnected : EventTypeNames::gamepaddisconnected;
+    m_pendingEvents.append(gamepad);
+    m_dispatchOneEventRunner.runAsync();
+}
+
+void NavigatorGamepad::dispatchOneEvent()
+{
+    ASSERT(window());
+    ASSERT(!m_pendingEvents.isEmpty());
+
+    Gamepad* gamepad = m_pendingEvents.takeFirst();
+    const AtomicString& eventName = gamepad->connected() ? EventTypeNames::gamepadconnected : EventTypeNames::gamepaddisconnected;
     window()->dispatchEvent(GamepadEvent::create(eventName, false, true, gamepad));
+
+    if (!m_pendingEvents.isEmpty())
+        m_dispatchOneEventRunner.runAsync();
 }
 
 NavigatorGamepad::NavigatorGamepad(LocalFrame* frame)
     : DOMWindowProperty(frame)
     , DeviceEventControllerBase(frame ? frame->page() : 0)
     , DOMWindowLifecycleObserver(frame ? frame->domWindow() : 0)
+    , m_dispatchOneEventRunner(this, &NavigatorGamepad::dispatchOneEvent)
 {
 }
 
 NavigatorGamepad::~NavigatorGamepad()
 {
 }
 
 const char* NavigatorGamepad::supplementName()
 {
     return "NavigatorGamepad";
 }
 
 void NavigatorGamepad::willDestroyGlobalObjectInFrame()
 {
     stopUpdating();
     DOMWindowProperty::willDestroyGlobalObjectInFrame();
 }
 
 void NavigatorGamepad::willDetachGlobalObjectFromFrame()
 {
     stopUpdating();
     DOMWindowProperty::willDetachGlobalObjectFromFrame();
 }
 
 void NavigatorGamepad::registerWithDispatcher()
 {
     GamepadDispatcher::instance().addController(this);
+    m_dispatchOneEventRunner.resume();
 }
 
 void NavigatorGamepad::unregisterWithDispatcher()
 {
+    m_dispatchOneEventRunner.suspend();
     GamepadDispatcher::instance().removeController(this);
 }
 
 bool NavigatorGamepad::hasLastData()
 {
     // Gamepad data is polled instead of pushed.
     return false;
 }
 
 static bool isGamepadEvent(const AtomicString& eventType)
 {
     return eventType == EventTypeNames::gamepadconnected || eventType == EventTypeNames::gamepaddisconnected;
 }
 
 void NavigatorGamepad::didAddEventListener(LocalDOMWindow*, const AtomicString& eventType)
 {
     if (RuntimeEnabledFeatures::gamepadEnabled() && isGamepadEvent(eventType)) {
         if (page() && page()->visibilityState() == PageVisibilityStateVisible)
             startUpdating();
         m_hasEventListener = true;
     }
 }
 
 void NavigatorGamepad::didRemoveEventListener(LocalDOMWindow* window, const AtomicString& eventType)
 {
     if (isGamepadEvent(eventType)
         && !window->hasEventListeners(EventTypeNames::gamepadconnected)
         && !window->hasEventListeners(EventTypeNames::gamepaddisconnected)) {
-        m_hasEventListener = false;
+        didRemoveGamepadEventListeners();
     }
 }
 
 void NavigatorGamepad::didRemoveAllEventListeners(LocalDOMWindow*)
 {
+    didRemoveGamepadEventListeners();
+}
+
+void NavigatorGamepad::didRemoveGamepadEventListeners()
+{
     m_hasEventListener = false;
+    m_dispatchOneEventRunner.stop();
+    m_pendingEvents.clear();
 }
 
 void NavigatorGamepad::pageVisibilityChanged()
 {
     // Inform the embedder whether it needs to provide gamepad data for us.
-    if (page()->visibilityState() == PageVisibilityStateVisible && (m_hasEventListener || m_gamepads || m_webkitGamepads))
+    bool visible = page()->visibilityState() == PageVisibilityStateVisible;
+    if (visible && (m_hasEventListener || m_gamepads || m_webkitGamepads))
         startUpdating();
     else
         stopUpdating();
+
+    if (!visible || !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);
+
+    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)) {
+            oldGamepad->setConnected(false);
+            m_pendingEvents.append(oldGamepad);
+        }
+        if (connectedGamepadChanged || (!oldWasConnected && newIsConnected)) {
+            m_pendingEvents.append(newGamepad);
+        }
+    }
+
+    if (!m_pendingEvents.isEmpty())
+        m_dispatchOneEventRunner.runAsync();
 }
 
 } // namespace WebCore