Refactor screen/monitor so that gfx::Screen returns monitor object.

ui/gfx/screen.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 UI_GFX_SCREEN_H_
 #define UI_GFX_SCREEN_H_
 #pragma once
 
 #include "ui/gfx/native_widget_types.h"
 #include "ui/gfx/point.h"
 #include "ui/gfx/rect.h"
-#include "ui/gfx/size.h"
 
 namespace gfx {
 
+class Monitor;
+class MonitorObserver;
+class ScreenImpl;
+
 // A utility class for getting various info about screen size, monitors,
-// cursor position, etc.
-// TODO(erikkay) add more of those methods here
+// cursor position, etc. The monitor object returned by Screen's method
+// is valid only until the next |GetMonitorXXX| method is called.
+// TODO(oshima): Implment monitor observers on other platforms and
+// remove above restruction. See crbug.com/122863 for details.
 class UI_EXPORT Screen {
  public:
   virtual ~Screen() {}
 
-#if defined(USE_ASH)
+#if defined(USE_AURA)
   // Sets the instance to use. This takes owernship of |screen|, deleting the
   // old instance. This is used on aura to avoid circular dependencies between
   // ui and aura.
-  static void SetInstance(Screen* screen);
+  static void SetInstance(ScreenImpl* screen);
 #endif
 
+  static void AddMonitorObserver(MonitorObserver* observer);
+  static void RemoveMonitorObserver(MonitorObserver* observer);
+
   // Returns the current absolute position of the mouse pointer.
   static gfx::Point GetCursorScreenPoint();
 
-  // Returns the work area of the monitor nearest the specified window.
-  static gfx::Rect GetMonitorWorkAreaNearestWindow(gfx::NativeView view);
-
-  // Returns the bounds of the monitor nearest the specified window.
-  static gfx::Rect GetMonitorAreaNearestWindow(gfx::NativeView view);
-
-  // Returns the work area of the monitor nearest the specified point.
-  static gfx::Rect GetMonitorWorkAreaNearestPoint(const gfx::Point& point);
-
-  // Returns the monitor area (not the work area, but the complete bounds) of
-  // the monitor nearest the specified point.
-  static gfx::Rect GetMonitorAreaNearestPoint(const gfx::Point& point);
-
-  // Returns the bounds of the work area of the primary monitor.
-  static gfx::Rect GetPrimaryMonitorWorkArea();
-
-  // Returns the bounds of the primary monitor.
-  static gfx::Rect GetPrimaryMonitorBounds();
-
-  // Returns the bounds of the work area of the monitor that most closely
-  // intersects the provided bounds.
-  static gfx::Rect GetMonitorWorkAreaMatching(
-      const gfx::Rect& match_rect);
-
   // Returns the window under the cursor.
   static gfx::NativeWindow GetWindowAtCursorScreenPoint();
 
-  // Returns the dimensions of the primary monitor in pixels.
-  static gfx::Size GetPrimaryMonitorSize();
-
   // Returns the number of monitors.
   // Mirrored displays are excluded; this method is intended to return the
   // number of distinct, usable displays.
   static int GetNumMonitors();
 
- protected:
-  virtual gfx::Point GetCursorScreenPointImpl() = 0;
-  virtual gfx::Rect GetMonitorWorkAreaNearestWindowImpl(
-      gfx::NativeView view) = 0;
-  virtual gfx::Rect GetMonitorAreaNearestWindowImpl(
-      gfx::NativeView view) = 0;
-  virtual gfx::Rect GetMonitorWorkAreaNearestPointImpl(
-      const gfx::Point& point) = 0;
-  virtual gfx::Rect GetMonitorAreaNearestPointImpl(const gfx::Point& point) = 0;
-  virtual gfx::NativeWindow GetWindowAtCursorScreenPointImpl() = 0;
-  virtual gfx::Size GetPrimaryMonitorSizeImpl() = 0;
-  virtual int GetNumMonitorsImpl() = 0;
+  // Returns the monitor nearest the specified window. See the comment at the
+  // top regarding the life sycle of |gfx::Monitor| object.
+  static const gfx::Monitor* GetMonitorNearestWindow(gfx::NativeView view);
 
-private:
-#if defined(USE_AURA)
-  // The singleton screen instance. Only used on aura.
-  static Screen* instance_;
-#endif
+  // Returns the the monitor nearest the specified point. See the comment at the
+  // top regarding the life sycle of |gfx::Monitor| object.
+  static const gfx::Monitor* GetMonitorNearestPoint(const gfx::Point& point);
+
+  // Returns the bounds of the work area of the primary monitor.  See
+  // the comment at the top regarding the life sycle of |gfx::Monitor|
+  // object.
+  static const gfx::Monitor* GetPrimaryMonitor();
+
+  // Returns the monitor that most closely intersects the provided bounds. See
+  // the comment at the top regarding the life sycle of |gfx::Monitor|
+  // object.
+  static const gfx::Monitor* GetMonitorMatching(const gfx::Rect& match_rect);
+
+  // Utility functions to get Monitor bounds/WorkArea bounds.
+  static gfx::Rect GetMonitorAreaNearestWindow(gfx::NativeView view);
+  static gfx::Rect GetMonitorWorkAreaNearestWindow(gfx::NativeView view);
+  static gfx::Rect GetMonitorAreaNearestPoint(const gfx::Point& point);
+  static gfx::Rect GetMonitorWorkAreaNearestPoint(const gfx::Point& point);
 };
 
 }  // namespace gfx
 
 #endif  // VIEWS_SCREEN_H_