aura: Re-enable XInput2 events.

ui/base/x/events_x.cc

Index: ui/base/x/events_x.cc
diff --git a/ui/base/x/events_x.cc b/ui/base/x/events_x.cc
index 329acbe5147d1a8a75fe1691d9b8b718b1a57c7d..bb65ba2aa4f0693ab6e3bb489a50e4bcb613e758 100644
--- a/ui/base/x/events_x.cc
+++ b/ui/base/x/events_x.cc
@@ -247,8 +247,23 @@ gfx::Point EventLocationFromNative(const base::NativeEvent& native_event) {
     case GenericEvent: {
       XIDeviceEvent* xievent =
           static_cast<XIDeviceEvent*>(native_event->xcookie.data);
-      return gfx::Point(static_cast<int>(xievent->event_x),
-                        static_cast<int>(xievent->event_y));
+
+      if (xievent->sourceid == xievent->deviceid) {
+        // This event is coming from a slave device. Read the position from the
+        // valuators, because the events reported for a slave device seems to be
+        // behind the master device by one event. See more on crbug.com/103981.
+        // The position in the valuators is in the global screen coordinates.
+        // But it is necessary to convert it into the window's coordinates.
+        // Prepare to be revolted.

[sadrul, 2011/11/21 01:30:29]

It's not all that bad, really.

+        double x = xievent->valuators.values[0] - (xievent->root_x -
+                                                   xievent->event_x);
+        double y = xievent->valuators.values[1] - (xievent->root_y -
+                                                   xievent->event_y);
+        return gfx::Point(static_cast<int>(x), static_cast<int>(y));
+      } else {
+        return gfx::Point(static_cast<int>(xievent->event_x),
+                          static_cast<int>(xievent->event_y));
+      }
     }
   }
   return gfx::Point();