Add the partial screen magnifier to Chrome OS.

ash/magnifier/partial_magnification_controller.h

Index: ash/magnifier/partial_magnification_controller.h
diff --git a/ash/magnifier/partial_magnification_controller.h b/ash/magnifier/partial_magnification_controller.h
new file mode 100644
index 0000000000000000000000000000000000000000..7908d97660fca13a979131b248ddf792449bb301
--- /dev/null
+++ b/ash/magnifier/partial_magnification_controller.h
@@ -0,0 +1,99 @@
+// 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 ASH_MAGNIFIER_PARTIAL_MAGNIFICATION_CONTROLLER_H_
+#define ASH_MAGNIFIER_PARTIAL_MAGNIFICATION_CONTROLLER_H_
+
+#include "ui/aura/window_observer.h"
+#include "ui/base/events/event_handler.h"
+#include "ui/gfx/point.h"
+#include "ui/views/widget/widget_observer.h"
+
+namespace aura {
+class RootWindow;
+}
+
+namespace ash {
+
+const float kDefaultPartialMagnifiedScale = 1.5f;
+const float kNonPartialMagnifiedScale = 1.0f;
+
+// Controls the partial screen magnifier, which is a small area of the screen
+// which is zoomed in.  The zoomed area follows the mouse cursor when enabled.
+class PartialMagnificationController
+  : public ui::EventHandler,
+    public aura::WindowObserver,
+    public views::WidgetObserver {
+ public:
+  PartialMagnificationController();
+  virtual ~PartialMagnificationController();
+
+  // Enables (or disables if |enabled| is false) partial screen magnifier
+  // feature.
+  virtual void SetEnabled(bool enabled);
+
+  bool is_enabled() const { return is_enabled_; }
+
+  // Sets the magnification ratio. 1.0f means no magnification.
+  void SetScale(float scale);
+
+  // Returns the current magnification ratio.
+  float GetScale() const { return scale_; }
+
+ private:
+  void OnMouseMove(const gfx::Point& location_in_root);
+
+  // Switch PartialMagnified RootWindow to |new_root_window|. This does
+  // following:
+  //  - Remove the magnifier from the current root window.
+  //  - Create a magnifier in the new root_window |new_root_window|.
+  //  - Switch the target window from current window to |new_root_window|.
+  void SwitchTargetRootWindow(aura::RootWindow* new_root_window);
+
+  // Returns the root window that contains the mouse cursor.
+  aura::RootWindow* GetCurrentRootWindow();
+
+  // Return true if the magnification scale > kMinPartialMagnifiedScaleThreshold
+  bool IsPartialMagnified() const;
+
+  // Create the magnifier window.
+  void CreateMagnifierWindow();
+
+  // Cleans up the window if needed.
+  void CloseMagnifierWindow();
+
+  // Removes this as an observer of the zoom widget and the root window.
+  void RemoveZoomWidgetObservers();
+
+  // ui::EventHandler overrides:
+  virtual ui::EventResult OnKeyEvent(ui::KeyEvent* event) OVERRIDE;
+  virtual ui::EventResult OnMouseEvent(ui::MouseEvent* event) OVERRIDE;
+  virtual ui::EventResult OnScrollEvent(ui::ScrollEvent* event) OVERRIDE;
+  virtual ui::EventResult OnTouchEvent(ui::TouchEvent* event) OVERRIDE;
+  virtual ui::EventResult OnGestureEvent(ui::GestureEvent* event) OVERRIDE;
+
+  // Overridden from WindowObserver:
+  virtual void OnWindowDestroying(aura::Window* window) OVERRIDE;
+
+  // Overridden from WidgetObserver:
+  virtual void OnWidgetClosing(views::Widget* widget) OVERRIDE;
+
+  // True if the magnified window is in motion of zooming or un-zooming effect.
+  // Otherwise, false.
+  bool is_on_zooming_;
+
+  bool is_enabled_;
+
+  // Current scale, origin (left-top) position of the magnification window.
+  float scale_;
+  gfx::Point origin_;
+
+  views::Widget* zoom_widget_;
+
+  DISALLOW_COPY_AND_ASSIGN(PartialMagnificationController);
+};
+
+}  // namespace ash
+
+#endif  // ASH_MAGNIFIER_PARTIAL_MAGNIFICATION_CONTROLLER_H_