Source code of Windows XP (NT5)
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#ifndef _DROPTGT_H_
#define _DROPTGT_H_
// There are two drag-drop support objects:
//
// CDropTargetWrap - This object takes a collection of drop-target
// objects and wraps them as one drop-target
// handler. The first drop-target wins over the
// the last one if there is a conflict in who
// will take the drop.
//
// CDelegateDropTarget - This class implements IDropTarget given an
// IDelegateDropTargetCB interface. It handles
// all hit testing, caching, and scrolling for you.
// Use this class by inheriting it in your derived
// class; it is not intended to be instantiated alone.
//
// Event notifications for HitTestDDT
#define HTDDT_ENTER 0
#define HTDDT_OVER 1
#define HTDDT_LEAVE 2
class CDelegateDropTarget : public IDropTarget
{
public:
// *** IDropTarget methods ***
virtual STDMETHODIMP DragEnter(IDataObject *pdtobj, DWORD grfKeyState, POINTL pt, DWORD *pdwEffect);
virtual STDMETHODIMP DragOver(DWORD grfKeyState, POINTL pt, DWORD *pdwEffect);
virtual STDMETHODIMP DragLeave(void);
virtual STDMETHODIMP Drop(IDataObject *pdtobj, DWORD grfKeyState, POINTL pt, DWORD *pdwEffect);
// *** Other methods to be implemented by derived class ***
virtual HRESULT GetWindowsDDT (HWND * phwndLock, HWND * phwndScroll) PURE;
virtual HRESULT HitTestDDT (UINT nEvent, LPPOINT ppt, DWORD_PTR * pdwId, DWORD *pdwEffect) PURE;
virtual HRESULT GetObjectDDT (DWORD_PTR dwId, REFIID riid, LPVOID * ppvObj) PURE;
virtual HRESULT OnDropDDT (IDropTarget *pdt, IDataObject *pdtobj,
DWORD * pgrfKeyState, POINTL pt, DWORD *pdwEffect) PURE;
friend IDropTarget* DropTargetWrap_CreateInstance(IDropTarget* pdtPrimary,
IDropTarget* pdtSecondary,
HWND hwnd, IDropTarget* pdt3 = NULL);
protected:
CDelegateDropTarget();
virtual ~CDelegateDropTarget();
BOOL IsValid() { return (_hwndLock && _hwndScroll); }
void SetCallback(IDelegateDropTargetCB* pdtcb);
HRESULT Init(); // init lock + scroll windows
friend IDropTarget* DelegateDropTarget_CreateInstance(IDelegateDropTargetCB* pdtcb);
private:
void _ReleaseCurrentDropTarget();
// the below are parameters we use to implement this IDropTarget
HWND _hwndLock;
HWND _hwndScroll;
// the object we are dragging
LPDATAOBJECT _pDataObj; // from DragEnter()/Drop()
// the below indicate the current drag state
BITBOOL _fPrime:1; // TRUE iff _itemOver/_grfKeyState is valid
DWORD_PTR _itemOver; // item we are visually dragging over
IDropTarget* _pdtCur; // drop target for _itemOver
DWORD _grfKeyState; // cached key state
DWORD _dwEffectOut; // last *pdwEffect out
POINT _ptLast; // last dragged position
// for scrolling
RECT _rcLockWindow; // WindowRect of hwnd for DAD_ENTER
AUTO_SCROLL_DATA _asd; // for auto scrolling
} ;
// dummy drop target to only call DAD_DragEnterEx() on DragEnter();
class CDropDummy : public IDropTarget
{
public:
// *** IUnknown ***
virtual STDMETHODIMP_(ULONG) AddRef(void);
virtual STDMETHODIMP_(ULONG) Release(void);
virtual STDMETHODIMP QueryInterface(REFIID riid, LPVOID * ppvObj);
// *** IDropTarget methods ***
virtual STDMETHODIMP DragEnter(IDataObject *pdtobj, DWORD grfKeyState, POINTL pt, DWORD *pdwEffect);
virtual STDMETHODIMP DragOver(DWORD grfKeyState, POINTL pt, DWORD *pdwEffect);
virtual STDMETHODIMP DragLeave(void)
{
DAD_DragLeave();
return(S_OK);
};
virtual STDMETHODIMP Drop(IDataObject *pdtobj, DWORD grfKeyState, POINTL pt, DWORD *pdwEffect)
{
DragLeave();
return(S_OK);
};
CDropDummy(HWND hwndLock) : _hwndLock(hwndLock), _cRef(1) { return; };
protected:
~CDropDummy() { return; };
private:
HWND _hwndLock; // window for dummy drop target.
int _cRef;
};
#endif // _DROPTGT_H_