CrOS Tablet Window management - Split Screen part I

ash/wm/overview/overview_window_drag_controller.h

+// Copyright 2017 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_OVERVIEW_WINDOW_DRAG_CONTROLLER_H_
+#define ASH_WM_OVERVIEW_OVERVIEW_WINDOW_DRAG_CONTROLLER_H_
+
+#include <memory>
+
+#include "ash/ash_export.h"
+#include "base/macros.h"
+#include "ui/gfx/geometry/point.h"
+#include "ui/gfx/geometry/rect.h"
+
+namespace ash {
+
+class WindowSelector;
+class WindowSelectorItem;
+class PhantomWindowController;
+class SplitViewController;
+
+// The drag controller for an overview window item in overview mode. It updates
+// the position of the corresponding window item using transform while dragging
+// and shows/hides the phantom window accordingly.
+class ASH_EXPORT OverviewWindowDragController {
+ public:
+  explicit OverviewWindowDragController(WindowSelector* window_selector);
+  ~OverviewWindowDragController();
+
+  void InitiateDrag(WindowSelectorItem* item,
+                    const gfx::Point& location_in_screen);
+  void Drag(const gfx::Point& location_in_screen);
+  void CompleteDrag();
+
+  WindowSelectorItem* item() { return item_; }
+
+ private:
+  enum SnapType { SNAP_LEFT, SNAP_RIGHT, SNAP_NONE };
+
+  void UpdatePhantomWindow(const gfx::Point& location_in_screen);
+  SnapType GetSnapType(const gfx::Point& location_in_screen);
+
+  void SnapToLeft();
+  void SnapToRight();
+
+  WindowSelector* window_selector_;
+
+  SplitViewController* split_view_controller_;
+
+  // Gives a previews of where the dragged window will end up.
+  std::unique_ptr<PhantomWindowController> phantom_window_controller_;
+
+  // The drag target window in the overview mode.
+  WindowSelectorItem* item_ = nullptr;
+
+  // The location of the initial mouse/touch/gesture event in screen.
+  gfx::Point initial_event_location_;

[varkha, 2017/06/21 01:51:52]

I suspect you could use previous_event_location_ for the same purpose with no
loss of clarity.

[xdai1, 2017/06/22 21:46:33]

You're right. Removed |initial_event_location_|. Thanks!

+
+  // The location of the previous mouse/touch/gesture event in screen.
+  gfx::Point previous_event_location_;
+
+  // Set to true once the bounds of |item_| changes.
+  bool did_move_ = false;
+
+  SnapType snap_type_ = SNAP_NONE;
+
+  DISALLOW_COPY_AND_ASSIGN(OverviewWindowDragController);
+};
+
+}  // namespace ash
+
+#endif  // ASH_WM_OVERVIEW_OVERVIEW_WINDOW_DRAG_CONTROLLER_H_