It is time.

ui/views/widget/drop_helper.h

-// Copyright (c) 2011 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 UI_VIEWS_WIDGET_DROP_HELPER_H_
-#define UI_VIEWS_WIDGET_DROP_HELPER_H_
-
-#include "base/basictypes.h"
-
-namespace gfx {
-class Point;
-}  // namespace gfx
-
-namespace ui {
-class OSExchangeData;
-}  // namespace ui
-using ui::OSExchangeData;
-
-namespace views {
-
-class RootView;
-class View;
-
-// DropHelper provides support for managing the view a drop is going to occur
-// at during dnd as well as sending the view the appropriate dnd methods.
-// DropHelper is intended to be used by a class that interacts with the system
-// drag and drop. The system class invokes OnDragOver as the mouse moves,
-// then either OnDragExit or OnDrop when the drop is done.
-class DropHelper {
- public:
-  explicit DropHelper(View* root_view);
-  ~DropHelper();
-
-  // Current view drop events are targeted at, may be NULL.
-  View* target_view() const { return target_view_; }
-
-  // Returns the RootView the DropHelper was created with.
-  View* root_view() const { return root_view_; }
-
-  // Resets the target_view_ to NULL if it equals view.
-  //
-  // This is invoked when a View is removed from the RootView to make sure
-  // we don't target a view that was removed during dnd.
-  void ResetTargetViewIfEquals(View* view);
-
-  // Invoked when a the mouse is dragged over the root view during a drag and
-  // drop operation. This method returns a bitmask of the types in DragDropTypes
-  // for the target view. If no view wants the drop, DRAG_NONE is returned.
-  int OnDragOver(const OSExchangeData& data,
-                 const gfx::Point& root_view_location,
-                 int drag_operation);
-
-  // Invoked when a the mouse is dragged out of the root view during a drag and
-  // drop operation.
-  void OnDragExit();
-
-  // Invoked when the user drops data on the root view during a drag and drop
-  // operation. See OnDragOver for details on return type.
-  //
-  // NOTE: implementations must invoke OnDragOver before invoking this,
-  // supplying the return value from OnDragOver as the drag_operation.
-  int OnDrop(const OSExchangeData& data,
-             const gfx::Point& root_view_location,
-             int drag_operation);
-
-  // Calculates the target view for a drop given the specified location in
-  // the coordinate system of the rootview. This tries to avoid continually
-  // querying CanDrop by returning target_view_ if the mouse is still over
-  // target_view_.
-  View* CalculateTargetView(const gfx::Point& root_view_location,
-                            const OSExchangeData& data,
-                            bool check_can_drop);
-
- private:
-  // Implementation of CalculateTargetView. If |deepest_view| is non-NULL it is
-  // set to the deepest descendant of the RootView that contains the point
-  // |root_view_location|
-  View* CalculateTargetViewImpl(const gfx::Point& root_view_location,
-                                const OSExchangeData& data,
-                                bool check_can_drop,
-                                View** deepest_view);
-
-  // Methods to send the appropriate drop notification to the targeted view.
-  // These do nothing if the target view is NULL.
-  void NotifyDragEntered(const OSExchangeData& data,
-                         const gfx::Point& root_view_location,
-                         int drag_operation);
-  int NotifyDragOver(const OSExchangeData& data,
-                     const gfx::Point& root_view_location,
-                     int drag_operation);
-  void NotifyDragExit();
-
-  // RootView we were created for.
-  View* root_view_;
-
-  // View we're targeting events at.
-  View* target_view_;
-
-  // The deepest view under the current drop coordinate.
-  View* deepest_view_;
-
-  DISALLOW_COPY_AND_ASSIGN(DropHelper);
-};
-
-}  // namespace views
-
-#endif  // UI_VIEWS_WIDGET_DROP_HELPER_H_