Added arrow key navigation to Overview Mode

ash/wm/overview/window_grid.h

Index: ash/wm/overview/window_grid.h
diff --git a/ash/wm/overview/window_grid.h b/ash/wm/overview/window_grid.h
new file mode 100644
index 0000000000000000000000000000000000000000..0513c50e90bba39cf42919bbd469063cad391a38
--- /dev/null
+++ b/ash/wm/overview/window_grid.h
@@ -0,0 +1,113 @@
+// 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 ASH_WM_OVERVIEW_WINDOW_GRID_H_
+#define ASH_WM_OVERVIEW_WINDOW_GRID_H_
+
+#include <vector>
+
+#include "ash/wm/overview/window_selector.h"
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+
+namespace aura {
+class Window;
+}
+
+namespace views {
+class Widget;
+}
+
+namespace ash {
+
+class WindowSelectorItem;
+
+// Represents a grid of windows in the Overview Mode in a particular root
+// window, and manages a selection widget that can be moved with the arrow keys.
+// The idea behind the movement strategy is that it should be possible to access
+// any window pressing a given arrow key repeatedly.
+//  +-------+  +-------+  +-------+
+//  |   0   |  |   1   |  |   2   |
+//  |       |  |       |  |       |

[flackr, 2014/06/03 17:12:07]

nit: These boxes probably don't need the extra empty line.

[Nina, 2014/06/04 20:21:13]

Done.

[flackr, 2014/06/04 22:25:06]

Sorry, to be specific, I meant you could remove lines 32, 36, and 40.

[Nina, 2014/06/05 18:04:34]

Done.

+//  +-------+  +-------+  +-------+
+//  +-------+  +-------+  +-------+
+//  |   3   |  |   4   |  |   5   |
+//  |       |  |       |  |       |
+//  +-------+  +-------+  +-------+
+//  +-------+
+//  |   6   |
+//  |       |
+//  +-------+
+// Example sequences:
+//  - Going right->left

[flackr, 2014/06/03 17:12:07]

nit: "Going left to right:" and "Going "top" to "bottom""

[Nina, 2014/06/04 20:21:13]

Done.

+//    0, 1, 2, 3, 4, 5, 6
+//  - Going down->up
+//    0, 3, 6, 1, 4, 2, 5
+// The selector is switched to the next window grid (if available) or wrapped if
+// it reaches the end of its movement sequence.
+class WindowGrid {
+ public:
+  WindowGrid(aura::Window* root_window,
+             const std::vector<WindowSelectorItem*>& window_list);
+  ~WindowGrid();
+
+  // Moves the selection widget to the specified |direction|. Returns true if,
+  // after moving, the widget is out of bounds.
+  bool Move(WindowSelector::Direction direction);
+
+  // Positions all the windows in the grid.
+  void PositionWindows(bool animate);
+
+  // Removes |window| from the grid, if present.
+  // RemoveWindow() repositions the items in the grid if necessary.

[flackr, 2014/06/03 17:12:07]

No need to mention method name since it's the comment for this method. Just
"Repositions the items in the grid if necessary."

[Nina, 2014/06/04 20:21:13]

Comment noted, this code has been removed.

+  void RemoveWindow(aura::Window* window);
+
+  // Returns the target selected window, or NULL if there is none selected.
+  WindowSelectorItem* SelectedWindow() const;
+
+  // Returns true if the grid has no more windows.
+  bool empty() const { return window_list_.empty(); }
+
+  // Returns true if the selection widget is active.
+  bool is_selecting() const { return selection_widget_ != NULL; }
+
+  // Returns the root window in which the grid displays the windows.
+  const aura::Window* root_window() const { return root_window_; }
+
+  const std::vector<WindowSelectorItem*>& window_list() const {
+    return window_list_.get();
+  }
+
+ private:
+  // Internal function to initialize the selection widget.
+  void InitSelectionWidget(WindowSelector::Direction direction);
+
+  // Updates |selected_index_| according to the specified |direction|. Returns
+  // |true| if the new selection index is out of this window grid bounds.
+  bool MoveSelectedIndex(WindowSelector::Direction direction);
+
+  // Returns the target bounds of the currently selected item.
+  const gfx::Rect GetSelectionBounds() const;
+
+  // Root window the grid is in.
+  aura::Window* root_window_;
+
+  // Vector containing all the windows in this grid.
+  ScopedVector<WindowSelectorItem> window_list_;
+
+  // Widget that indicates to the user which is the selected window.
+  scoped_ptr<views::Widget> selection_widget_;
+
+  // Current selected window position.
+  size_t selected_index_;
+
+  // Number of columns in the grid.
+  size_t num_columns_;
+
+  DISALLOW_COPY_AND_ASSIGN(WindowGrid);
+};
+
+}  // namespace ash
+
+#endif  // ASH_WM_OVERVIEW_WINDOW_GRID_H_