Regularly poll the X11 event queue.

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 "base/memory/scoped_ptr.h"
 #include "ui/events/events_export.h"
 #include "ui/events/platform/platform_event_source.h"
@@ skipping 10 matching lines @@
 
 // A PlatformEventSource implementation for reading events from X11 server and
 // dispatching the events to the appropriate dispatcher.
 class EVENTS_EXPORT X11EventSource : public PlatformEventSource {
  public:
   explicit X11EventSource(XDisplay* display);
   ~X11EventSource() override;
 
   static X11EventSource* GetInstance();
 
-  // Called by the glib source dispatch function. Processes all (if any)
-  // available X events.
-  void DispatchXEvents();
+  // Processes pending X events.  Returns true if any events were dispatched.
+  // This function should be called repeatedly until it returns false to
+  // ensure all events are processed.
+  bool DispatchXEvents();
 
   // Blocks on the X11 event queue until we receive notification from the
   // xserver that |w| has been mapped; StructureNotifyMask events on |w| are
   // pulled out from the queue and dispatched out of order.
   //
   // For those that know X11, this is really a wrapper around XWindowEvent
   // which still makes sure the preempted event is dispatched instead of
   // dropped on the floor. This method exists because mapping a window is
   // asynchronous (and we receive an XEvent when mapped), while there are also
   // functions which require a mapped window.
   void BlockUntilWindowMapped(XID window);
 
  protected:
   XDisplay* display() { return display_; }
 
  private:
   // PlatformEventSource:
   uint32_t DispatchEvent(XEvent* xevent) override;
   void StopCurrentEventStream() override;
   void OnDispatcherListChanged() override;
 
   // The connection to the X11 server used to receive the events.
   XDisplay* display_;
 
   // Keeps track of whether this source should continue to dispatch all the
   // available events.
   bool continue_stream_;
 
+  // Dispatch one event at a time.
+  bool dispatch_one_event_per_loop_;
+
   scoped_ptr<X11HotplugEventHandler> hotplug_event_handler_;
 
   DISALLOW_COPY_AND_ASSIGN(X11EventSource);
 };
 
 }  // namespace ui
 
 #endif  // UI_EVENTS_PLATFORM_X11_X11_EVENT_SOURCE_H_