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// Copyright 2008, Google Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#ifndef BASE_BASE_DROP_TARGET_H__
#define BASE_BASE_DROP_TARGET_H__
#include <atlbase.h>
#include <objidl.h>
#include <shobjidl.h>
#include "base/basictypes.h"
// 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.
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);
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.
CComPtr<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_;
// 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__
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