Gamepad API: add support for gamepadconnected and gamepaddisconnected events

Source/core/frame/DOMWindow.cpp

Index: Source/core/frame/DOMWindow.cpp
diff --git a/Source/core/frame/DOMWindow.cpp b/Source/core/frame/DOMWindow.cpp
index f301a446854c952d9e5d615c8fa947f8bcde5072..cce5251f7b7e3b2b6ee802e0067131f0285bd7da 100644
--- a/Source/core/frame/DOMWindow.cpp
+++ b/Source/core/frame/DOMWindow.cpp
@@ -105,6 +105,9 @@
 #include "wtf/text/WTFString.h"
 #include <algorithm>
 
+// FIXME: this is a layering vilation.

[Inactive, 2014/03/14 19:46:08]

Yes, we don't want that :)

[kbalazs, 2014/03/14 23:51:27]

Done.

+#include "modules/gamepad/NavigatorGamepad.h"
+
 using std::min;
 using std::max;
 
@@ -1518,6 +1521,13 @@ bool DOMWindow::addEventListener(const AtomicString& eventType, PassRefPtr<Event
             // Subframes return false from allowsBeforeUnloadListeners.
             UseCounter::count(document(), UseCounter::SubFrameBeforeUnloadRegistered);
         }
+    } else if (eventType == EventTypeNames::gamepadconnected || eventType == EventTypeNames::gamepaddisconnected) {

[sof, 2014/03/14 20:52:43]

Just above these special cases, DOMWindow observers are notified about the event
listener being added. I think you can hook in your sampling trigger that way.
Grep for implementations of DOMWindowLifecycleObserver to see how.

[kbalazs, 2014/03/14 23:51:27]

Wonderful, thanks. Together with
FrameLoaderClientImpl::dispatchDidClearWindowObjectInWorld this lead me to a
solution.

+        // If an event listener is added for gamepad events sample the gamepads once to start monitoring gamepad state.
+        // FIXME: we need to instantiate NavigatorGamepad here so that it can listen to the events.
+        // Otherwise it would only be created when js calls getGamepads() or webkitGetGamepads() and we cannot assume that
+        // it will happen before a gamepad is connected. But this is a layering violation because NavigatorGamepad lives
+        // in modules.
+        NavigatorGamepad::getGamepads(navigator());

[Inactive, 2014/03/14 19:46:08]

You should probably take a look at
FrameLoaderClientImpl::dispatchDidClearWindowObjectInWorld(DOMWrapperWorld*
world) but abarth@ may have a better idea.

[kbalazs, 2014/03/14 23:51:27]

Done.

     }
 
     return true;