Handles the failures of output state change.

chromeos/display/output_configurator.h

 // Copyright (c) 2012 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 CHROMEOS_DISPLAY_OUTPUT_CONFIGURATOR_H_
 #define CHROMEOS_DISPLAY_OUTPUT_CONFIGURATOR_H_
 
 #include "base/basictypes.h"
 #include "base/event_types.h"
 #include "base/observer_list.h"
@@ skipping 30 matching lines @@
 // This class interacts directly with the underlying Xrandr API to manipulate
 // CTRCs and Outputs.  It will likely grow more state, over time, or expose
 // Output info in other ways as more of the Chrome display code grows up around
 // it.
 class CHROMEOS_EXPORT OutputConfigurator : public MessageLoop::Dispatcher {
  public:
   class Observer {
    public:
     // Called when the change of the display mode finished.  It will usually
     // start the fading in the displays.
-    virtual void OnDisplayModeChanged() = 0;
+    virtual void OnDisplayModeChanged() {};
+
+    // Called when the change of the display mode is issued but failed.
+    virtual void OnDisplayModeChangeFailed() {};
   };
 
   OutputConfigurator();
   virtual ~OutputConfigurator();
 
   int connected_output_count() const { return connected_output_count_; }
 
   OutputState output_state() const { return output_state_; }
 
   // Called when the user hits ctrl-F4 to request a display mode change.
@@ skipping 51 matching lines @@
   // The timer to delay sending the notification of OnDisplayChanged(). See also
   // the comments in Dispatch().
   scoped_ptr<base::OneShotTimer<OutputConfigurator> > notification_timer_;
 
   DISALLOW_COPY_AND_ASSIGN(OutputConfigurator);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROMEOS_DISPLAY_OUTPUT_CONFIGURATOR_H_