Implement workspace scrubbing

ash/wm/workspace/workspace_cycler.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 ASH_WM_WORKSPACE_WORKSPACE_CYCLER_H_
+#define ASH_WM_WORKSPACE_WORKSPACE_CYCLER_H_
+
+#include "ash/ash_export.h"
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "ui/aura/window_observer.h"
+#include "ui/base/events/event_handler.h"
+#include "ui/gfx/point.h"
+
+namespace ash {
+namespace internal {
+
+class WorkspaceManager;
+
+// Class to enable quick workspace switching (scrubbing) via ctrl-up-drag /
+// ctrl-down-drag.
+// Note: this is experimental and disables ctrl-clicks. It should not be
+// enabled other than through flags until we implement 3 finger drag as the
+// mechanism to invoke it. At that point we will add test coverage.
+class ASH_EXPORT WorkspaceCycler : public aura::WindowObserver,
+                                   public ui::EventHandler {
+ public:
+  explicit WorkspaceCycler(WorkspaceManager* workspace_manager);
+  virtual ~WorkspaceCycler();
+
+ private:
+

[sky, 2012/11/28 15:15:34]

nit: no newline.

+  // Initiates scrubbing.
+  void StartScrubbing();
+
+  // Stops scrubbing.
+  void StopScrubbing();
+
+  // aura::WindowObserver overrides:
+  virtual void OnWindowDestroyed(aura::Window* window) OVERRIDE;
+
+  // ui::EventHandler overrides:
+  virtual ui::EventResult OnMouseEvent(ui::MouseEvent* event) OVERRIDE;
+
+  WorkspaceManager* workspace_manager_;
+
+  enum ScrubState {

[sky, 2012/11/28 15:15:34]

Style guide says enums are typically first in a section.

+    SCRUBBING,
+    CANCELLED_SCRUBBING,
+    NOT_SCRUBBING
+  };
+
+  ScrubState scrub_state_;
+
+  // The position of the event which most recently switched the active
+  // workspace. If scrubbing has just begun, |last_transition_position_| is set
+  // to the position of the event which initiated scrubbing.
+  gfx::Point last_transition_position_;

[sky, 2012/11/28 15:15:34]

Document coordinates, in fact I think you should name this
last_transition_position_in_root_ to make it clear.

+
+  // The window of the active workspace when workspace scrubbing was initiated.
+  aura::Window* initial_workspace_window_;
+
+  DISALLOW_COPY_AND_ASSIGN(WorkspaceCycler);
+};
+
+}  // namespace internal
+}  // namespace ash
+
+#endif  // ASH_WM_WORKSPACE_WORKSPACE_CYCLER_H_