droptgt.cpp

wxGTK 是 wxWidgets 的 linux GTK+ (>2.2.3)版本。wxWidgets 是一个跨平台的 GUI 框架

    if ( !ScreenToClient(m_hwnd, (POINT *)&pt) )
    {
        wxLogLastError(wxT("ScreenToClient"));
    }

    // first ask the drop target if it wants data
    if ( m_pTarget->OnDrop(pt.x, pt.y) ) {
        // it does, so give it the data source
        m_pTarget->SetDataSource(pIDataSource);

        // and now it has the data
        wxDragResult rc = ConvertDragEffectToResult(
            GetDropEffect(grfKeyState, m_pTarget->GetDefaultAction()));
        rc = m_pTarget->OnData(pt.x, pt.y, rc);
        if ( wxIsDragResultOk(rc) ) {
            // operation succeeded
            *pdwEffect = ConvertDragResultToEffect(rc);
        }
        //else: *pdwEffect is already DROPEFFECT_NONE
    }
    //else: OnDrop() returned false, no need to copy data

    // release the held object
    RELEASE_AND_NULL(m_pIDataObject);

    return S_OK;
}

// ============================================================================
// wxDropTarget implementation
// ============================================================================

// ----------------------------------------------------------------------------
// ctor/dtor
// ----------------------------------------------------------------------------

wxDropTarget::wxDropTarget(wxDataObject *dataObj)
            : wxDropTargetBase(dataObj)
{
    // create an IDropTarget implementation which will notify us about d&d
    // operations.
    m_pIDropTarget = new wxIDropTarget(this);
    m_pIDropTarget->AddRef();
}

wxDropTarget::~wxDropTarget()
{
    ReleaseInterface(m_pIDropTarget);
}

// ----------------------------------------------------------------------------
// [un]register drop handler
// ----------------------------------------------------------------------------

bool wxDropTarget::Register(WXHWND hwnd)
{
    // FIXME
    // RegisterDragDrop not available on Windows CE >= 400?
    // Or maybe we can dynamically load them from ceshell.dll
    // or similar.
#if defined(__WXWINCE__) && _WIN32_WCE >= 400
    wxUnusedVar(hwnd);
    return false;
#else
    HRESULT hr;

    // May exist in later WinCE versions
#ifndef __WXWINCE__
    hr = ::CoLockObjectExternal(m_pIDropTarget, TRUE, FALSE);
    if ( FAILED(hr) ) {
        wxLogApiError(wxT("CoLockObjectExternal"), hr);
        return false;
    }
#endif

    hr = ::RegisterDragDrop((HWND) hwnd, m_pIDropTarget);
    if ( FAILED(hr) ) {
    // May exist in later WinCE versions
#ifndef __WXWINCE__
        ::CoLockObjectExternal(m_pIDropTarget, FALSE, FALSE);
#endif
        wxLogApiError(wxT("RegisterDragDrop"), hr);
        return false;
    }

    // we will need the window handle for coords transformation later
    m_pIDropTarget->SetHwnd((HWND)hwnd);

    return true;
#endif
}

void wxDropTarget::Revoke(WXHWND hwnd)
{
#if defined(__WXWINCE__) && _WIN32_WCE >= 400
    // Not available, see note above
    wxUnusedVar(hwnd);
#else
    HRESULT hr = ::RevokeDragDrop((HWND) hwnd);

    if ( FAILED(hr) ) {
        wxLogApiError(wxT("RevokeDragDrop"), hr);
    }

    // May exist in later WinCE versions
#ifndef __WXWINCE__
    ::CoLockObjectExternal(m_pIDropTarget, FALSE, TRUE);
#endif

    m_pIDropTarget->SetHwnd(0);
#endif
}

// ----------------------------------------------------------------------------
// base class pure virtuals
// ----------------------------------------------------------------------------

// OnDrop() is called only if we previously returned true from
// IsAcceptedData(), so no need to check anything here
bool wxDropTarget::OnDrop(wxCoord WXUNUSED(x), wxCoord WXUNUSED(y))
{
    return true;
}

// copy the data from the data source to the target data object
bool wxDropTarget::GetData()
{
    wxDataFormat format = GetSupportedFormat(m_pIDataSource);
    if ( format == wxDF_INVALID ) {
        // this is strange because IsAcceptedData() succeeded previously!
        wxFAIL_MSG(wxT("strange - did supported formats list change?"));

        return false;
    }

    STGMEDIUM stm;
    FORMATETC fmtMemory;
    fmtMemory.cfFormat  = format;
    fmtMemory.ptd       = NULL;
    fmtMemory.dwAspect  = DVASPECT_CONTENT;
    fmtMemory.lindex    = -1;
    fmtMemory.tymed     = TYMED_HGLOBAL;  // TODO to add other media

    bool rc = false;

    HRESULT hr = m_pIDataSource->GetData(&fmtMemory, &stm);
    if ( SUCCEEDED(hr) ) {
        IDataObject *dataObject = m_dataObject->GetInterface();

        hr = dataObject->SetData(&fmtMemory, &stm, TRUE);
        if ( SUCCEEDED(hr) ) {
            rc = true;
        }
        else {
            wxLogApiError(wxT("IDataObject::SetData()"), hr);
        }
    }
    else {
        wxLogApiError(wxT("IDataObject::GetData()"), hr);
    }

    return rc;
}

// ----------------------------------------------------------------------------
// callbacks used by wxIDropTarget
// ----------------------------------------------------------------------------

// we need a data source, so wxIDropTarget gives it to us using this function
void wxDropTarget::SetDataSource(IDataObject *pIDataSource)
{
    m_pIDataSource = pIDataSource;
}

// determine if we accept data of this type
bool wxDropTarget::IsAcceptedData(IDataObject *pIDataSource) const
{
    return GetSupportedFormat(pIDataSource) != wxDF_INVALID;
}

// ----------------------------------------------------------------------------
// helper functions
// ----------------------------------------------------------------------------

wxDataFormat wxDropTarget::GetSupportedFormat(IDataObject *pIDataSource) const
{
    // this strucutre describes a data of any type (first field will be
    // changing) being passed through global memory block.
    static FORMATETC s_fmtMemory = {
        0,
        NULL,
        DVASPECT_CONTENT,
        -1,
        TYMED_HGLOBAL       // TODO is it worth supporting other tymeds here?
    };

    // get the list of supported formats
    size_t nFormats = m_dataObject->GetFormatCount(wxDataObject::Set);
    wxDataFormat format;
    wxDataFormat *formats;
    formats = nFormats == 1 ? &format :  new wxDataFormat[nFormats];

    m_dataObject->GetAllFormats(formats, wxDataObject::Set);

    // cycle through all supported formats
    size_t n;
    for ( n = 0; n < nFormats; n++ ) {
        s_fmtMemory.cfFormat = formats[n];

        // NB: don't use SUCCEEDED macro here: QueryGetData returns S_FALSE
        //     for file drag and drop (format == CF_HDROP)
        if ( pIDataSource->QueryGetData(&s_fmtMemory) == S_OK ) {
            format = formats[n];

            break;
        }
    }

    if ( formats != &format ) {
        // free memory if we allocated it
        delete [] formats;
    }

    return n < nFormats ? format : wxFormatInvalid;
}

// ----------------------------------------------------------------------------
// private functions
// ----------------------------------------------------------------------------

static wxDragResult ConvertDragEffectToResult(DWORD dwEffect)
{
    switch ( dwEffect ) {
        case DROPEFFECT_COPY:
            return wxDragCopy;

        case DROPEFFECT_LINK:
            return wxDragLink;

        case DROPEFFECT_MOVE:
            return wxDragMove;

        default:
            wxFAIL_MSG(wxT("invalid value in ConvertDragEffectToResult"));
            // fall through

        case DROPEFFECT_NONE:
            return wxDragNone;
    }
}

static DWORD ConvertDragResultToEffect(wxDragResult result)
{
    switch ( result ) {
        case wxDragCopy:
            return DROPEFFECT_COPY;

        case wxDragLink:
            return DROPEFFECT_LINK;

        case wxDragMove:
            return DROPEFFECT_MOVE;

        default:
            wxFAIL_MSG(wxT("invalid value in ConvertDragResultToEffect"));
            // fall through

        case wxDragNone:
            return DROPEFFECT_NONE;
    }
}

#endif // wxUSE_OLE && wxUSE_DRAG_AND_DROP