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Visual C++

DropTargetImpl.h：源码内容
							#if !defined(AFX_DROPTARGETIMPL_H__20010406_CE55_D769_D3CA_0080AD509054__INCLUDED_)
#define AFX_DROPTARGETIMPL_H__20010406_CE55_D769_D3CA_0080AD509054__INCLUDED_
#pragma once
//////////////////////////////////////////////////////////////////////////////
// IDropTargetImpl
class ATL_NO_VTABLE IDropTargetImpl : public IDropTarget
{
public:
   IDropTargetImpl() : m_pFolder(NULL), m_hwndTarget(NULL), m_fAcceptFmt(false)
   { 
   }
   ~IDropTargetImpl()
   {
      if( m_pFolder!=NULL ) m_pFolder->Release();
   }
   HRESULT _Init(CFolder *pFolder, HWND hWnd)
   {
      ATLTRACE(_T("CDropTarget::_Initn"));
      ATLASSERT(pFolder);
      m_pFolder = pFolder;
      m_pFolder->AddRef();
      m_hwndTarget = hWnd;
      return S_OK;
   }
// Attributes
public:
   CFolder *m_pFolder;
   HWND m_hwndTarget;
   bool m_fAcceptFmt;
// IDropTarget
public:
   STDMETHOD(DragEnter)(LPDATAOBJECT pDataObj, 
                        DWORD dwKeyState, 
                        POINTL, 
                        LPDWORD pdwEffect)
   {
      ATLTRACE(_T("CDropTarget::DragEntern"));
      ATLASSERT(pDataObj);
      // Does the drag source provide our CF types?
      m_fAcceptFmt = false;
      if( !m_fAcceptFmt ) {
         FORMATETC fe = { CF_HDROP, NULL, DVASPECT_CONTENT, -1, TYMED_HGLOBAL };
         m_fAcceptFmt = (S_OK == pDataObj->QueryGetData(&fe));
      }
      if( !m_fAcceptFmt ) {
         FORMATETC fe = { _Module.m_CFSTR_FILEDESCRIPTOR, NULL, DVASPECT_CONTENT, -1, TYMED_HGLOBAL };
         m_fAcceptFmt = (S_OK == pDataObj->QueryGetData(&fe));
      }
      *pdwEffect = _QueryDrop(dwKeyState, pdwEffect);
      return S_OK;
   }
   STDMETHOD(DragOver)(DWORD dwKeyState, POINTL /*pt*/, LPDWORD pdwEffect)
   {
      *pdwEffect = _QueryDrop(dwKeyState, pdwEffect);
      return S_OK;
   }
   
   STDMETHOD(DragLeave)(VOID)
   {
      ATLTRACE(_T("CDropTarget::DragLeaven"));
      m_fAcceptFmt = false;
      return S_OK;
   }
   STDMETHOD(Drop)(LPDATAOBJECT pDataObj,
                   DWORD dwKeyState,
                   POINTL /*pt*/,
                   LPDWORD pdwEffect)
   {
      ATLTRACE(_T("CDropTarget::Dropn"));
      ATLASSERT(pDataObj);
      ATLASSERT(pdwEffect);
      ATLASSERT(m_pFolder);
      // Determine drop effect...
      DWORD dwDropEffect = _QueryDrop(dwKeyState, pdwEffect);
      *pdwEffect = DROPEFFECT_NONE; // default to failed/cancelled
      // Did we accept this drop effect?
      if( dwDropEffect==DROPEFFECT_NONE ) return S_OK;
      // Drop data...
      HRESULT Hr;
      if( SUCCEEDED(Hr = m_pFolder->_DoDrop(pDataObj, dwDropEffect) ) ) {
         // Our DoDrop() method returns S_FALSE if something was cancelled.
         // In this case, we let the droptype fall back to DROPEFFECT_COPY
         // so nothing gets deleted.
         *pdwEffect = ( Hr==S_OK ? dwDropEffect : DROPEFFECT_COPY );
      }
      m_pFolder->_SendViewMessage(m_hwndTarget, WM_COMMAND, ID_VIEW_REFRESH);
      return S_OK;
   }
// Implementation
private:
   DWORD _QueryDrop(DWORD dwKeyState, LPDWORD pdwEffect)
   {
      ATLASSERT(pdwEffect);
      if( !m_fAcceptFmt ) return DROPEFFECT_NONE;
      DWORD dwMask = _GetDropEffectFromKeyState(dwKeyState);
      if( (*pdwEffect) & dwMask ) return (*pdwEffect) & dwMask;
      // Map common alternatives
      if( (*pdwEffect) & DROPEFFECT_COPY ) return DROPEFFECT_COPY;
      if( (*pdwEffect) & DROPEFFECT_MOVE ) return DROPEFFECT_MOVE;
      return DROPEFFECT_NONE;
   }
   DWORD _GetDropEffectFromKeyState(DWORD dwKeyState)
   {
      // "Move" is the default.
      // We don't support DROPEFFECT_LINK operations.
      DWORD dwDropEffect = DROPEFFECT_MOVE;
      if( dwKeyState & MK_CONTROL ) dwDropEffect = DROPEFFECT_COPY;
      return dwDropEffect;
   }
};
#endif // !defined(AFX_DROPTARGETIMPL_H__20010406_CE55_D769_D3CA_0080AD509054__INCLUDED_)

						