| // Copyright (c) 2006-2008 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 BASE_BASE_DROP_TARGET_H_ |
| #define BASE_BASE_DROP_TARGET_H_ |
| |
| #include <objidl.h> |
| |
| #include "base/ref_counted.h" |
| |
| struct IDropTargetHelper; |
| |
| // 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 BaseDropTarget 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 BaseDropTarget : public IDropTarget { |
| public: |
| // Create a new BaseDropTarget associating it with the given HWND. |
| explicit BaseDropTarget(HWND hwnd); |
| virtual ~BaseDropTarget(); |
| |
| // When suspend is set to |true|, the drop target does not receive drops from |
| // drags initiated within the owning HWND. |
| // TODO(beng): (http://b/1085385) figure out how we will handle legitimate |
| // drag-drop operations within the same HWND, such as dragging |
| // selected text to an edit field. |
| void set_suspend(bool suspend) { suspend_ = suspend; } |
| |
| // 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); |
| |
| // Return the drag identity. |
| static int32 GetDragIdentity() { return drag_identity_; } |
| |
| 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 drag identity (id). An up-counter that increases when the cursor first |
| // moves over the HWND in a DnD session (OnDragEnter). 0 is reserved to mean |
| // the "no/unknown" identity, and is used for initialization. The identity is |
| // sent to the renderer in drag enter notifications. Note: the identity value |
| // is passed over the renderer NPAPI interface to gears, so use int32 instead |
| // of int here. |
| static int32 drag_identity_; |
| |
| // 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_; |
| |
| // Whether or not we are currently processing drag notifications for drags |
| // initiated in this window. |
| bool suspend_; |
| |
| LONG ref_count_; |
| |
| DISALLOW_EVIL_CONSTRUCTORS(BaseDropTarget); |
| }; |
| |
| #endif // BASE_BASE_DROP_TARGET_H_ |