droptgt.cpp

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/*
 * DROPTGT.CPP
 * Component Cosmo Chapter 13
 *
 * Implementation of the DropTarget object.
 *
 * Copyright (c)1993-1995 Microsoft Corporation, All Rights Reserved
 *
 * Kraig Brockschmidt, Microsoft
 * Internet  :  [e-mail]
 * Compuserve:  >INTERNET:[e-mail]
 */


#include "cocosmo.h"



/*
 * CDropTarget::CDropTarget
 * CDropTarget::~CDropTarget
 *
 * Constructor Parameters:
 *  pDoc            PCCosmoDoc of the document containing us.
 */

CDropTarget::CDropTarget(PCCosmoDoc pDoc)
    {
    m_cRef=0;
    m_pDoc=pDoc;

    m_pIDataObject=NULL;
    return;
    }


CDropTarget::~CDropTarget(void)
    {
    return;
    }




/*
 * CDropTarget::QueryInterface
 * CDropTarget::AddRef
 * CDropTarget::Release
 *
 * Purpose:
 *  IUnknown members for CDropTarget object.
 */

STDMETHODIMP CDropTarget::QueryInterface(REFIID riid, PPVOID ppv)
    {
    *ppv=NULL;

    if (IID_IUnknown==riid || IID_IDropTarget==riid)
        *ppv=this;

    if (NULL!=*ppv)
        {
        ((LPUNKNOWN)*ppv)->AddRef();
        return NOERROR;
        }

    return ResultFromScode(E_NOINTERFACE);
    }


STDMETHODIMP_(ULONG) CDropTarget::AddRef(void)
    {
    return ++m_cRef;
    }

STDMETHODIMP_(ULONG) CDropTarget::Release(void)
    {
     if (0!=--m_cRef)
        return m_cRef;

    delete this;
    return 0;
    }





/*
 * CDropTarget::DragEnter
 *
 * Purpose:
 *  Indicates that data in a drag operation has been dragged over
 *  our window that's a potential target.  We are to decide if it's
 *  something in which we're interested.
 *
 * Parameters:
 *  pIDataSource    LPDATAOBJECT providing the source data.
 *  grfKeyState     DWORD flags: states of keys and mouse buttons.
 *  pt              POINTL coordinates in the client space of
 *                  the document.
 *  pdwEffect       LPDWORD into which we'll place the appropriate
 *                  effect flag for this point.
 *
 * Return Value:
 *  HRESULT         NOERROR
 */

STDMETHODIMP CDropTarget::DragEnter(LPDATAOBJECT pIDataSource
    , DWORD grfKeyState, POINTL pt, LPDWORD pdwEffect)
    {
    HWND        hWnd;

    m_pIDataObject=NULL;

    if (!m_pDoc->FQueryPasteFromData(pIDataSource))
        {
        *pdwEffect=DROPEFFECT_NONE;
        return NOERROR;
        }

    *pdwEffect=DROPEFFECT_MOVE;

    if (grfKeyState & MK_CONTROL)
        *pdwEffect=DROPEFFECT_COPY;

    m_pIDataObject=pIDataSource;
    m_pIDataObject->AddRef();

    hWnd=m_pDoc->Window();
    BringWindowToTop(hWnd);
    UpdateWindow(hWnd);
    m_pDoc->DropSelectTargetWindow();

    return NOERROR;
    }






/*
 * CDropTarget::DragOver
 *
 * Purpose:
 *  Indicates that the mouse was moved inside the window represented
 *  by this drop target.  This happens on every WM_MOUSEMOVE, so
 *  this function should be very efficient.
 *
 * Parameters:
 *  grfKeyState     DWORD providing the current keyboard and
 *                  mouse states
 *  pt              POINTL where the mouse currently is.
 *  pdwEffect       LPDWORD in which to store the effect flag
 *                  for this point.
 *
 * Return Value:
 *  HRESULT         NOERROR
 */

STDMETHODIMP CDropTarget::DragOver(DWORD grfKeyState, POINTL pt
    , LPDWORD pdwEffect)
    {
    if (NULL==m_pIDataObject)
        {
        *pdwEffect=DROPEFFECT_NONE;
        return NOERROR;
        }

    *pdwEffect=DROPEFFECT_MOVE;

    if (grfKeyState & MK_CONTROL)
        *pdwEffect=DROPEFFECT_COPY;

    return NOERROR;
    }






/*
 * CDropTarget::DragLeave
 *
 * Purpose:
 *  Informs the drop target that the operation has left its window.
 *
 * Parameters:
 *  None
 *
 * Return Value:
 *  HRESULT         NOERROR
 */

STDMETHODIMP CDropTarget::DragLeave(void)
    {
    m_pDoc->DropSelectTargetWindow();
    ReleaseInterface(m_pIDataObject);
    return NOERROR;
    }





/*
 * CDropTarget::Drop
 *
 * Purpose:
 *  Instructs the drop target to paste the data that was just now
 *  dropped on it.
 *
 * Parameters:
 *  pIDataSource    LPDATAOBJECT from which we'll paste.
 *  grfKeyState     DWORD providing current keyboard/mouse state.
 *  pt              POINTL at which the drop occurred.
 *  pdwEffect       LPDWORD in which to store what you did.
 *
 * Return Value:
 *  HRESULT         NOERROR
 */

STDMETHODIMP CDropTarget::Drop(LPDATAOBJECT pIDataSource
    , DWORD grfKeyState, POINTL pt, LPDWORD pdwEffect)
    {
    BOOL        fRet=TRUE;

    *pdwEffect=DROPEFFECT_NONE;

    if (NULL==m_pIDataObject)
        return ResultFromScode(E_FAIL);

    DragLeave();

    if (m_pDoc->m_fDragSource)
        return ResultFromScode(E_FAIL);

    fRet=m_pDoc->PasteFromData(pIDataSource);

    if (!fRet)
        return ResultFromScode(E_FAIL);

    *pdwEffect=DROPEFFECT_MOVE;

    if (grfKeyState & MK_CONTROL)
        *pdwEffect=DROPEFFECT_COPY;

    return NOERROR;
    }