chromeos: Support turning displays off in extended mode.

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 <vector>
 
 #include "base/basictypes.h"
@@ skipping 86 matching lines @@
   // Detects displays first time from unknown state.
   void Start();
 
   // Stop handling display configuration events/requests.
   void Stop();
 
   // Called when powerd notifies us that some set of displays should be turned
   // on or off.  This requires enabling or disabling the CRTC associated with
   // the display(s) in question so that the low power state is engaged.
   // If |force_probe| is true, the displays will be configured even if
-  // |power_state| matches |power_state_|.
-  bool SetDisplayPower(DisplayPowerState power_state, bool force_probe);
+  // |power_state| matches |power_state_|. If
+  // |only_if_single_internal_display| is true, the state will not be
+  // changed if multiple displays are connected or if the display is not
+  // internal.
+  bool SetDisplayPower(DisplayPowerState power_state,
+                       bool force_probe,
+                       bool only_if_single_internal_display);

[Daniel Erat, 2013/03/27 23:15:19]

I would've preferred to let callers deal with the "only if single internal"
check, but that seems tricky due us needing to reprobe every time this is called
-- I think that improving that is a bit more than we should try to deal with for
27.

 
   // Force switching the display mode to |new_state|. Returns false if
   // it was called in a single-head or headless mode.
   bool SetDisplayMode(OutputState new_state);
 
   // Called when an RRNotify event is received.  The implementation is
   // interested in the cases of RRNotify events which correspond to output
   // add/remove events.  Note that Output add/remove events are sent in response
   // to our own reconfiguration operations so spurious events are common.
   // Spurious events will have no effect.
@@ skipping 129 matching lines @@
 
   // Indicates the time at which |output_state_| was entered.
   base::TimeTicks last_enter_state_time_;
 
   DISALLOW_COPY_AND_ASSIGN(OutputConfigurator);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROMEOS_DISPLAY_OUTPUT_CONFIGURATOR_H_