X11: Avoid round-tripping to get the cursor position

ui/events/platform/x11/x11_event_source.h

 // Copyright 2014 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.
 
 #ifndef UI_EVENTS_PLATFORM_X11_X11_EVENT_SOURCE_H_
 #define UI_EVENTS_PLATFORM_X11_X11_EVENT_SOURCE_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 59 matching lines @@
 
   void BlockUntilWindowUnmapped(XID window);
 
   XDisplay* display() { return display_; }
 
   // Returns the timestamp of the event currently being dispatched.  Falls back
   // on GetCurrentServerTime() if there's no event being dispatched, or if the
   // current event does not have a timestamp.
   Time GetTimestamp();
 
+  // If an event is being dispatched, copies the event into *|event| and
+  // returns true.  Otherwise *|event| is untouched and this returns false.
+  const XEvent* get_dispatching_event() const { return dispatching_event_; }

[sadrul, 2016/10/07 02:12:51]

Exposing the raw XEvent feels more icky. I would prefer something like 'bool
GetRootCursorLocationFromCurrentEvent(gfx::Point* location)' or something like
that.

[Tom (Use chromium acct), 2016/10/07 21:13:18]

Done.

+
   void StopCurrentEventStream();
   void OnDispatcherListChanged();
 
  protected:
   // Extracts cookie data from |xevent| if it's of GenericType, and dispatches
   // the event. This function also frees up the cookie data after dispatch is
   // complete.
   void ExtractCookieDataDispatchEvent(XEvent* xevent);
 
   // Handles updates after event has been dispatched.
@@ skipping 11 matching lines @@
   static X11EventSource* instance_;
 
   X11EventSourceDelegate* delegate_;
 
   // The connection to the X11 server used to receive the events.
   XDisplay* display_;
 
   // The timestamp of the event being dispatched.
   Time event_timestamp_;
 
+  // The event being dispatched, or nullptr if there is none.
+  XEvent* dispatching_event_;
+
   // State necessary for UpdateLastSeenServerTime
   bool dummy_initialized_;
   XWindow dummy_window_;
   XAtom dummy_atom_;
   std::unique_ptr<XScopedEventSelector> dummy_window_events_;
 
   // Keeps track of whether this source should continue to dispatch all the
   // available events.
   bool continue_stream_ = true;
 
   std::unique_ptr<X11HotplugEventHandler> hotplug_event_handler_;
 
   DISALLOW_COPY_AND_ASSIGN(X11EventSource);
 };
 
 }  // namespace ui
 
 #endif  // UI_EVENTS_PLATFORM_X11_X11_EVENT_SOURCE_H_