It is time.

ui/base/dragdrop/drop_target_win.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_BASE_DRAGDROP_DROP_TARGET_WIN_H_
-#define UI_BASE_DRAGDROP_DROP_TARGET_WIN_H_
-
-#include <objidl.h>
-
-#include "base/memory/ref_counted.h"
-#include "ui/base/ui_base_export.h"
-
-// Windows interface.
-struct IDropTargetHelper;
-
-namespace ui {
-
-// A DropTarget implementation that takes care of the nitty gritty
-// of dnd. While this class is concrete, subclasses will most likely
-// want to override various OnXXX methods.
-//
-// Because DropTarget is ref counted you shouldn't delete it directly,
-// rather wrap it in a scoped_refptr. Be sure and invoke RevokeDragDrop(m_hWnd)
-// before the HWND is deleted too.
-//
-// This class is meant to be used in a STA and is not multithread-safe.
-class UI_BASE_EXPORT DropTargetWin : public IDropTarget {
- public:
-  // Create a new DropTarget associating it with the given HWND.
-  explicit DropTargetWin(HWND hwnd);
-  virtual ~DropTargetWin();
-
-  // IDropTarget implementation:
-  HRESULT __stdcall DragEnter(IDataObject* data_object,
-                              DWORD key_state,
-                              POINTL cursor_position,
-                              DWORD* effect);
-  HRESULT __stdcall DragOver(DWORD key_state,
-                             POINTL cursor_position,
-                             DWORD* effect);
-  HRESULT __stdcall DragLeave();
-  HRESULT __stdcall Drop(IDataObject* data_object,
-                         DWORD key_state,
-                         POINTL cursor_position,
-                         DWORD* effect);
-
-  // IUnknown implementation:
-  HRESULT __stdcall QueryInterface(const IID& iid, void** object);
-  ULONG __stdcall AddRef();
-  ULONG __stdcall Release();
-
- protected:
-  // Returns the hosting HWND.
-  HWND GetHWND() { return hwnd_; }
-
-  // Invoked when the cursor first moves over the hwnd during a dnd session.
-  // This should return a bitmask of the supported drop operations:
-  // DROPEFFECT_NONE, DROPEFFECT_COPY, DROPEFFECT_LINK and/or
-  // DROPEFFECT_MOVE.
-  virtual DWORD OnDragEnter(IDataObject* data_object,
-                            DWORD key_state,
-                            POINT cursor_position,
-                            DWORD effect);
-
-  // Invoked when the cursor moves over the window during a dnd session.
-  // This should return a bitmask of the supported drop operations:
-  // DROPEFFECT_NONE, DROPEFFECT_COPY, DROPEFFECT_LINK and/or
-  // DROPEFFECT_MOVE.
-  virtual DWORD OnDragOver(IDataObject* data_object,
-                           DWORD key_state,
-                           POINT cursor_position,
-                           DWORD effect);
-
-  // Invoked when the cursor moves outside the bounds of the hwnd during a
-  // dnd session.
-  virtual void OnDragLeave(IDataObject* data_object);
-
-  // Invoked when the drop ends on the window. This should return the operation
-  // that was taken.
-  virtual DWORD OnDrop(IDataObject* data_object,
-                       DWORD key_state,
-                       POINT cursor_position,
-                       DWORD effect);
-
- private:
-  // Returns the cached drop helper, creating one if necessary. The returned
-  // object is not addrefed. May return NULL if the object couldn't be created.
-  static IDropTargetHelper* DropHelper();
-
-  // The data object currently being dragged over this drop target.
-  scoped_refptr<IDataObject> current_data_object_;
-
-  // A helper object that is used to provide drag image support while the mouse
-  // is dragging over the content area.
-  //
-  // DO NOT ACCESS DIRECTLY! Use DropHelper() instead, which will lazily create
-  // this if it doesn't exist yet. This object can take tens of milliseconds to
-  // create, and we don't want to block any window opening for this, especially
-  // since often, DnD will never be used. Instead, we force this penalty to the
-  // first time it is actually used.
-  static IDropTargetHelper* cached_drop_target_helper_;
-
-  // The HWND of the source. This HWND is used to determine coordinates for
-  // mouse events that are sent to the renderer notifying various drag states.
-  HWND hwnd_;
-
-  LONG ref_count_;
-
-  DISALLOW_COPY_AND_ASSIGN(DropTargetWin);
-};
-
-}  // namespace ui
-
-#endif  // UI_BASE_DRAGDROP_DROP_TARGET_WIN_H_