Extract the code of showing a dragging window on another display from PhantomWindowController.

ash/wm/drag_window_controller.h

Index: ash/wm/drag_window_controller.h
diff --git a/ash/wm/drag_window_controller.h b/ash/wm/drag_window_controller.h
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+// 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_DRAG_WINDOW_CONTROLLER_H_
+#define ASH_WM_DRAG_WINDOW_CONTROLLER_H_
+
+#include "ash/ash_export.h"
+#include "base/basictypes.h"
+#include "base/gtest_prod_util.h"
+#include "base/memory/scoped_ptr.h"
+#include "ui/gfx/display.h"
+#include "ui/gfx/rect.h"
+
+namespace aura {
+class Window;
+}
+
+namespace ui {
+class Layer;
+}
+
+namespace views {
+class Widget;
+}
+
+namespace ash {
+namespace internal {
+
+// DragWindowController is responsible for showing a semi-transparent window
+// while dragging a window across displays.
+class ASH_EXPORT DragWindowController {
+ public:
+  explicit DragWindowController(aura::Window* window);
+  virtual ~DragWindowController();
+
+  // Sets the display where the window is placed after the window is dropped.
+  void SetDestinationDisplay(const gfx::Display& dst_display);
+
+  // Shows the drag window at the specified location (coordinates of the
+  // parent). If |layer| is non-NULL, it is shown on top of the drag window.
+  // |layer| is owned by the caller.
+  // This does not immediately show the window.
+  void Show();
+
+  // Hides the drag window.
+  void Hide();
+
+  // This is used to set bounds for the drag window immediately. This should
+  // be called only when the drag window is already visible.
+  void SetBounds(const gfx::Rect& bounds);
+
+  // Sets the opacity of the drag window.
+  void SetOpacity(float opacity);
+
+ private:
+  FRIEND_TEST_ALL_PREFIXES(WorkspaceWindowResizerTest, DragWindowController);
+
+  // Creates and shows the |drag_widget_| at |bounds|.
+  // |layer| is shown on top of the drag window if it is non-NULL.
+  // |layer| is not owned by this object.
+  void CreateDragWidget(const gfx::Rect& bounds);
+
+  // Sets bounds of the drag window. The window is shown on |dst_display_|
+  // if its id() is valid. Otherwise, a display nearest to |bounds| is chosen.
+  void SetBoundsInternal(const gfx::Rect& bounds);
+
+  // Recreates a fresh layer for |window_| and all its child windows.
+  void RecreateWindowLayers();
+
+  // Window the drag window is placed beneath.
+  aura::Window* window_;
+
+  // The display where the drag is placed. When dst_display_.id() is
+  // kInvalidDisplayID (i.e. the default), a display nearest to the current
+  // |bounds_| is automatically used.
+  gfx::Display dst_display_;
+
+  // Initially the bounds of |window_|. Each time Show() is invoked
+  // |start_bounds_| is then reset to the bounds of |drag_widget_| and
+  // |bounds_| is set to the value passed into Show(). The animation animates
+  // between these two values.
+  gfx::Rect bounds_;
+
+  views::Widget* drag_widget_;
+
+  // The copy of window_->layer() and its children. This object is the owner of
+  // the layer.
+  ui::Layer* layer_;
+
+  DISALLOW_COPY_AND_ASSIGN(DragWindowController);
+};
+
+}  // namespace internal
+}  // namespace ash
+
+#endif  // ASH_WM_DRAG_WINDOW_CONTROLLER_H_