Add Fade-out/Fade-in animation during output-configuration change.

chromeos/display/output_configurator.h

Index: chromeos/display/output_configurator.h
diff --git a/chromeos/display/output_configurator.h b/chromeos/display/output_configurator.h
index 672a989413e1b7d0279db747ce16e5448a420548..22262c227ad8de8d41393a02cf5a12f44f95c539 100644
--- a/chromeos/display/output_configurator.h
+++ b/chromeos/display/output_configurator.h
@@ -6,6 +6,7 @@
 #define CHROMEOS_DISPLAY_OUTPUT_CONFIGURATOR_H_
 
 #include "base/basictypes.h"
+#include "base/callback.h"
 #include "base/event_types.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop.h"
@@ -57,11 +58,34 @@ enum State {
 // it.
 class CHROMEOS_EXPORT OutputConfigurator : public MessageLoop::Dispatcher {
  public:
+  // AnimationDelegate is responsible for making visual effect around the change
+  // of output configurations.  Typically it makes fade-out the displays before
+  // the transition and fade-in again after the transition finished.
+  class AnimationDelegate {

[Ben Goodger (Google), 2012/07/27 17:17:07]

I don't like how this is called "Animation*" since Animation to me implies
something very tied to the UI.

Can this instead be Observer or something like that?

e.g. class OutputConfiguratorObserver

[Jun Mukai, 2012/07/30 11:28:45]

Agree to rename this class, but I'm afraid that what this class does is not an
observer's task, since WillDisplayModeChange() accepts a callback and runs it. 
I think "observer" will just receive several events, right?

Then, I rather think to reorganize the code again like:
- create OutputConfiguratorObserver which triggers OnDisplayModeChanged() only
- ash::Shell doesn't have chromeos::OutputConfigurator directly.  Rather it has
ash::OutputConfigurator, which provides the interface to
chromeos::OutputConfigurator but conducts the fade-out animation before the
actual task.
- ash::OutputConfigurator inherits OutputConfiguratorObserver so that it knows
when fade-in animation will run.

Let me take a day to do this.

+   public:
+    virtual ~AnimationDelegate() {}
+
+    // Called when the change of display mode is scheduled.  It will usually
+    // start fading out the displays.  It also has to run |callback| once
+    // the visual effect has finished.
+    virtual void WillDisplayModeChange(base::Closure callback) {
+      callback.Run();
+    }
+
+    // Called when the change of the display mode finished.  It will usually
+    // start the fading in the displays.
+    virtual void OnDisplayModeChanged() {}
+  };
+
   OutputConfigurator();
   virtual ~OutputConfigurator();
 
   State output_state() const { return output_state_; }
 
+  void set_animation_delegate(AnimationDelegate* animation_delegate) {
+    animation_delegate_.reset(animation_delegate);
+  }
+
   // Called when the user hits ctrl-F4 to request a display mode change.
   // This method should only return false if it was called in a single-head or
   // headless mode.
@@ -85,6 +109,10 @@ class CHROMEOS_EXPORT OutputConfigurator : public MessageLoop::Dispatcher {
   virtual bool Dispatch(const base::NativeEvent& event) OVERRIDE;
 
  private:
+  // The actual task of changing display mode.  Usually this is called by the
+  // |animation_delegate_|.
+  void SetDisplayModeInternal(State new_state);
+
   // Updates |output_count_|, |output_cache_|, |mirror_supported_|,
   // |primary_output_index_|, and |secondary_output_index_| with new data.
   // Returns true if the update succeeded or false if it was skipped since no
@@ -156,6 +184,8 @@ class CHROMEOS_EXPORT OutputConfigurator : public MessageLoop::Dispatcher {
   // This is used for rotating display modes.
   State output_state_;
 
+  scoped_ptr<AnimationDelegate> animation_delegate_;
+
   DISALLOW_COPY_AND_ASSIGN(OutputConfigurator);
 };