aura: Turn XInput2 back on.

ui/base/x/events_x.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/base/events.h"
 
 #include <X11/Xlib.h>
 #include <X11/extensions/XInput2.h>
 #include <string.h>
 
@@ skipping 238 matching lines @@
 gfx::Point EventLocationFromNative(const base::NativeEvent& native_event) {
   switch (native_event->type) {
     case ButtonPress:
     case ButtonRelease:
       return gfx::Point(native_event->xbutton.x, native_event->xbutton.y);
     case MotionNotify:
       return gfx::Point(native_event->xmotion.x, native_event->xmotion.y);
     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));
+
+      // Read the position from the valuators, because the location reported in
+      // event_x/event_y seems to be different (and doesn't match for events
+      // coming from slave device and master device) from the values in the
+      // valuators. 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. If the valuator is not set, that means
+      // the value hasn't changed, and so we can use the value from
+      // event_x/event_y (which are in the window's coordinates).
+      double* valuators = xievent->valuators.values;
+
+      double x = xievent->event_x;
+      if (XIMaskIsSet(xievent->valuators.mask, 0))
+        x = *valuators++ - (xievent->root_x - xievent->event_x);
+
+      double y = xievent->event_y;
+      if (XIMaskIsSet(xievent->valuators.mask, 1))
+        y = *valuators++ - (xievent->root_y - xievent->event_y);
+
+      return gfx::Point(static_cast<int>(x), static_cast<int>(y));
     }
   }
   return gfx::Point();
 }
 
 KeyboardCode KeyboardCodeFromNative(const base::NativeEvent& native_event) {
   return KeyboardCodeFromXKeyEvent(native_event);
 }
 
 bool IsMouseEvent(const base::NativeEvent& native_event) {
@@ skipping 109 matching lines @@
   // Make sure we use atom from current xdisplay, which may
   // change during the test.
   noop->xclient.message_type = XInternAtom(
       base::MessagePumpX::GetDefaultXDisplay(),
       "noop", False);
 #endif
   return noop;
 }
 
 }  // namespace ui