DROPSRC.CPP

/* 
 * DROPSRC.CPP 
 * Patron Chapter 20 
 * 
 * Implementation of a DropSource object. 
 * 
 * Copyright (c)1993-1995 Microsoft Corporation, All Rights Reserved 
 * 
 * Kraig Brockschmidt, Microsoft 
 * Internet  :  kraigb@microsoft.com 
 * Compuserve:  >INTERNET:kraigb@microsoft.com 
 */ 
 
 
#include "patron.h" 
 
 
/* 
 * CDropSource::CDropSource 
 * CDropSource::~CDropSource 
 * 
 * Constructor Parameters: 
 *  None 
 */ 
 
CDropSource::CDropSource(void) 
    { 
    m_cRef=0; 
    return; 
    } 
 
CDropSource::~CDropSource(void) 
    { 
    return; 
    } 
 
 
 
 
/* 
 * CDropSource::QueryInterface 
 * CDropSource::AddRef 
 * CDropSource::Release 
 * 
 * Purpose: 
 *  IUnknown members for CDropSource object. 
 */ 
 
STDMETHODIMP CDropSource::QueryInterface(REFIID riid, PPVOID ppv) 
    { 
    *ppv=NULL; 
 
    if (IID_IUnknown==riid || IID_IDropSource==riid) 
        *ppv=this; 
 
    if (NULL!=*ppv) 
        { 
        ((LPUNKNOWN)*ppv)->AddRef(); 
        return NOERROR; 
        } 
 
    return ResultFromScode(E_NOINTERFACE); 
    } 
 
 
STDMETHODIMP_(ULONG) CDropSource::AddRef(void) 
    { 
    return ++m_cRef; 
    } 
 
STDMETHODIMP_(ULONG) CDropSource::Release(void) 
    { 
    if (0!=--m_cRef) 
        return m_cRef; 
 
    delete this; 
    return 0; 
    } 
 
 
 
 
 
/* 
 * CDropSource::QueryDragContinue 
 * 
 * Purpose: 
 *  Determines whether to continue a drag operation or cancel it. 
 * 
 * Parameters: 
 *  fEsc            BOOL indicating that the ESC key was pressed. 
 *  grfKeyState     DWORD providing states of keys and mouse buttons 
 * 
 * Return Value: 
 *  HRESULT         DRAGDROP_S_CANCEL to stop the drag, 
 *                  DRAGDROP_S_DROP to drop the data where it is, 
 *                  or NOERROR to continue. 
 */ 
 
STDMETHODIMP CDropSource::QueryContinueDrag(BOOL fEsc, DWORD grfKeyState) 
    { 
    if (fEsc) 
        return ResultFromScode(DRAGDROP_S_CANCEL); 
 
    if (!(grfKeyState & MK_LBUTTON)) 
        return ResultFromScode(DRAGDROP_S_DROP); 
 
    return NOERROR; 
    } 
 
 
 
 
 
 
/* 
 * CDropSource::GiveFeedback 
 * 
 * Purpose: 
 *  Provides cursor feedback to the user since the source task 
 *  always has the mouse capture.  We can also provide any other 
 *  type of feedback above cursors if we so desire. 
 * 
 * Parameters: 
 *  dwEffect        DWORD effect flags returned from the last target 
 * 
 * Return Value: 
 *  HRESULT         NOERROR if you set a cursor yourself or 
 *                  DRAGDROP_S_USEDEFAULTCURSORS to let OLE do 
 *                  the work. 
 */ 
 
STDMETHODIMP CDropSource::GiveFeedback(DWORD dwEffect) 
    { 
    return ResultFromScode(DRAGDROP_S_USEDEFAULTCURSORS); 
    }