DROPTGT.CPP

/* 
 * DROPTGT.CPP 
 * Cosmo Chapter 21 
 * 
 * Implementation of the IDropTarget interface. 
 * 
 * Copyright (c)1993-1995 Microsoft Corporation, All Rights Reserved 
 * 
 * Kraig Brockschmidt, Microsoft 
 * Internet  :  kraigb@microsoft.com 
 * Compuserve:  >INTERNET:kraigb@microsoft.com 
 */ 
 
 
#include "cosmo.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 we're interested in or not. 
 * 
 * Parameters: 
 *  pIDataSource    LPDATAOBJECT providing the source data. 
 *  grfKeyState     DWORD flags: states of keys and mouse buttons. 
 *  pt              POINTL coordinates in the document client space. 
 *  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; 
 
    /* 
     * 1.  Check if we can paste from the pIDataSource we're 
     *     provided. We already made this nice useful function 
     *     to test. 
     */ 
 
    m_pIDataObject=NULL; 
 
    if (!m_pDoc->FQueryPasteFromData(pIDataSource)) 
        { 
        *pdwEffect=DROPEFFECT_NONE; 
        return NOERROR; 
        } 
 
 
    /* 
     * 2.  We can always drop anywhere in our document, 
     *     so pt is uninteresting. 
     */ 
 
 
    /* 
     * 3. We return either a COPY or MOVE effect flag, depending on 
     *    the state of the grfKeyState flags.  We MOVE on no key or 
     *    Shift key, COPY on Ctrl key. 
     */ 
 
    //Default is move 
    *pdwEffect=DROPEFFECT_MOVE; 
 
    if (grfKeyState & MK_CONTROL) 
        *pdwEffect=DROPEFFECT_COPY; 
 
    /* 
     * 4. We really don't need to keep the IDataObject around since 
     *    we're not interested in it in DragOver.  However, we'll 
     *    save it just for demonstration. 
     */ 
    m_pIDataObject=pIDataSource; 
    m_pIDataObject->AddRef(); 
 
    /* 
     * 5.  We always accept drops of our data on us, so we only need 
     *     to provide some UI feedback here which we do by inverting 
     *     the edge of the polyline window in this document.  We'll 
     *     remove this in DragLeave and in Drop.  DragOver won't 
     *     effect it since we can always drop. 
     * 
     *     Since we're inverting a border, insure that this window is 
     *     on top. 
     */ 
 
    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 current keyboard/mouse states 
 *  pt              POINTL where the mouse currently is. 
 *  pdwEffect       LPDWORD 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; 
        } 
 
    //We can always drop; return effect flags based on keys. 
    *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) 
    { 
    //1.  Remove the UI feedback 
   m_pDoc->DropSelectTargetWindow(); 
 
   //2.  Release the held IDataObject 
   ReleaseInterface(m_pIDataObject); 
         
    return NOERROR; 
    } 
 
 
 
 
 
/* 
 * CDropTarget::Drop 
 * 
 * Purpose: 
 *  Instructs the drop target to paste 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 to store what you do with the data. 
 * 
 * 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); 
 
    //1.  Remove the UI feedback, release pointer 
    DragLeave(); 
     
    //No point in drag-drop to ourselves (for Cosmo, at least) 
    if (m_pDoc->m_fDragSource) 
        return ResultFromScode(E_FAIL); 
 
    //2.  Try a paste 
    fRet=m_pDoc->PasteFromData(pIDataSource); 
 
    //3.  Store the effect 
    if (!fRet) 
        return ResultFromScode(E_FAIL); 
 
    *pdwEffect=DROPEFFECT_MOVE; 
 
    if (grfKeyState & MK_CONTROL) 
        *pdwEffect=DROPEFFECT_COPY; 
 
    return NOERROR; 
    }