Gamepad: honor page visibility

Source/modules/gamepad/NavigatorGamepad.cpp

Index: Source/modules/gamepad/NavigatorGamepad.cpp
diff --git a/Source/modules/gamepad/NavigatorGamepad.cpp b/Source/modules/gamepad/NavigatorGamepad.cpp
index d1c006ef9a76fdb2b6725626b327a8a675a79c49..38ac468eaba9b6ade51f98a4ea237bd53467cb01 100644
--- a/Source/modules/gamepad/NavigatorGamepad.cpp
+++ b/Source/modules/gamepad/NavigatorGamepad.cpp
@@ -36,6 +36,7 @@
 #include "modules/gamepad/GamepadEvent.h"
 #include "modules/gamepad/GamepadList.h"
 #include "modules/gamepad/WebKitGamepadList.h"
+#include "wtf/TemporaryChange.h"
 
 namespace WebCore {
 
@@ -134,16 +135,10 @@ void NavigatorGamepad::didConnectOrDisconnectGamepad(unsigned index, const blink
     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();
 
@@ -154,14 +149,14 @@ void NavigatorGamepad::didConnectOrDisconnectGamepad(unsigned index, const blink
     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)
 {
 }
 
@@ -177,12 +172,14 @@ const char* NavigatorGamepad::supplementName()
 void NavigatorGamepad::willDestroyGlobalObjectInFrame()
 {
     stopUpdating();
+    invalidateCanContinueDispatchingSentinel();
     DOMWindowProperty::willDestroyGlobalObjectInFrame();
 }
 
 void NavigatorGamepad::willDetachGlobalObjectFromFrame()
 {
     stopUpdating();
+    invalidateCanContinueDispatchingSentinel();
     DOMWindowProperty::willDetachGlobalObjectFromFrame();
 }
 
@@ -211,8 +208,6 @@ PassRefPtrWillBeRawPtr<Event> NavigatorGamepad::getLastEvent()
 
 bool NavigatorGamepad::isNullEvent(Event*)
 {
-    // This is called only when hasLastData() is true.
-    ASSERT_NOT_REACHED();
     return false;
 }
 
@@ -235,10 +230,11 @@ void NavigatorGamepad::didAddEventListener(DOMWindow*, const AtomicString& event
     }
 }
 
-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*)
@@ -246,4 +242,63 @@ 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