Split Screen mode implementation

athena/wm/bezel_controller.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 ATHENA_WM_BEZEL_CONTROLLER_H_
 #define ATHENA_WM_BEZEL_CONTROLLER_H_
 
 #include "ui/events/event_handler.h"
 
 namespace aura {
@@ skipping 17 matching lines @@
   enum Bezel { BEZEL_NONE, BEZEL_LEFT, BEZEL_RIGHT, BEZEL_TOP, BEZEL_BOTTOM };
 
   // Responsible for handling scroll gestures initiated from the bezel.
   // Two touch points are need to perform the bezel scroll gesture from
   // the left and right bezel.
   class ScrollDelegate {
    public:
     virtual ~ScrollDelegate() {}
 
     // Beginning of a bezel scroll gesture started from the |bezel|.
+    // |delta| is the difference between the x-coordinate of the current scroll
+    // position and the bezel. It will be zero or negative for the right bezel.
     virtual void ScrollBegin(Bezel bezel, float delta) = 0;
 
     // End of the current bezel scroll
     virtual void ScrollEnd() = 0;
 
     // Update of the scroll position for the currently active bezel scroll.
+    // |delta| is the difference between the x-coordinate of the current scroll
+    // position and the bezel. It will be zero or negative for the right bezel.

[oshima, 2014/08/08 16:45:34]

nit: you may refer to the comment in ScrollBegin for |delta| instead of
repeating the comment.

[mfomitchev, 2014/08/08 17:40:50]

Done.

     virtual void ScrollUpdate(float delta) = 0;
 
     // Should return false if the delegate isn't going to react to the scroll
     // events.
     virtual bool CanScroll() = 0;
   };
 
   explicit BezelController(aura::Window* container);
   virtual ~BezelController() {}
 
   // Set the delegate to handle the gestures from left and right bezels.
   // Two touch points are need to perform the bezel scroll gesture from
   // the left and right bezel.
   void set_left_right_delegate(ScrollDelegate* delegate) {
     left_right_delegate_ = delegate;
   }
 
  private:
   enum State {
     NONE,
     IGNORE_CURRENT_SCROLL,
     BEZEL_GESTURE_STARTED,
     BEZEL_SCROLLING_ONE_FINGER,
     BEZEL_SCROLLING_TWO_FINGERS,
   };
 
-  // Calculates the distance from |position| to the |bezel|.
-  float GetDistance(const gfx::PointF& position, Bezel bezel);
-
-  // |scroll_position| only needs to be passed in the scrolling state
-  void SetState(State state, const gfx::PointF& scroll_position);
+  void SetState(State state);
+  // |scroll_delta| only needs to be passed when |state| is one of the
+  // BEZEL_SROLLING states.
+  void SetState(State state, float scroll_delta);
 
   // Returns the bezel corresponding to the |location| or BEZEL_NONE if the
   // location is outside of the bezel area.
   Bezel GetBezel(const gfx::PointF& location);
 
   // ui::EventHandler overrides
   virtual void OnGestureEvent(ui::GestureEvent* event) OVERRIDE;
 
   aura::Window* container_;
 
   State state_;
 
   // The bezel where the currently active scroll was started.
   Bezel scroll_bezel_;
 
   // The target of the bezel scroll gesture. Used to filter out other gestures
   // when the bezel scroll is in progress.
   ui::EventTarget* scroll_target_;
 
   // Responsible for handling gestures started from the left and right bezels.
   // Not owned.
   ScrollDelegate* left_right_delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(BezelController);
 };
 
 }  // namespace athena
 
 #endif  // ATHENA_WM_BEZEL_CONTROLLER_H_