private int QueryGetData(long /*int*/ pFormatetc) {
    if (transferAgents == null) return COM.E_FAIL;
    TransferData transferData = new TransferData();
    transferData.formatetc = new FORMATETC();
    COM.MoveMemory(transferData.formatetc, pFormatetc, FORMATETC.sizeof);
    transferData.type = transferData.formatetc.cfFormat;

    // is this type supported by the transfer agent?
    for (int i = 0; i < transferAgents.length; i++) {
      Transfer transfer = transferAgents[i];
      if (transfer != null && transfer.isSupportedType(transferData)) return COM.S_OK;
    }

    return COM.DV_E_FORMATETC;
  }
  private int GetData(long /*int*/ pFormatetc, long /*int*/ pmedium) {
    /* Called by a data consumer to obtain data from a source data object.
       The GetData method renders the data described in the specified FORMATETC
       structure and transfers it through the specified STGMEDIUM structure.
       The caller then assumes responsibility for releasing the STGMEDIUM structure.
    */
    if (pFormatetc == 0 || pmedium == 0) return COM.E_INVALIDARG;

    if (QueryGetData(pFormatetc) != COM.S_OK) return COM.DV_E_FORMATETC;

    TransferData transferData = new TransferData();
    transferData.formatetc = new FORMATETC();
    COM.MoveMemory(transferData.formatetc, pFormatetc, FORMATETC.sizeof);
    transferData.type = transferData.formatetc.cfFormat;
    transferData.stgmedium = new STGMEDIUM();
    transferData.result = COM.E_FAIL;

    DNDEvent event = new DNDEvent();
    event.widget = this;
    event.time = OS.GetMessageTime();
    event.dataType = transferData;
    notifyListeners(DND.DragSetData, event);

    if (!event.doit) return COM.E_FAIL;

    // get matching transfer agent to perform conversion
    Transfer transfer = null;
    for (int i = 0; i < transferAgents.length; i++) {
      Transfer transferAgent = transferAgents[i];
      if (transferAgent != null && transferAgent.isSupportedType(transferData)) {
        transfer = transferAgent;
        break;
      }
    }

    if (transfer == null) return COM.DV_E_FORMATETC;
    transfer.javaToNative(event.data, transferData);
    if (transferData.result != COM.S_OK) return transferData.result;
    COM.MoveMemory(pmedium, transferData.stgmedium, STGMEDIUM.sizeof);
    return transferData.result;
  }
  /**
   * This implementation of <code>javaToNative</code> converts an ImageData object represented by
   * java <code>ImageData</code> to a platform specific representation.
   *
   * @param object a java <code>ImageData</code> containing the ImageData to be converted
   * @param transferData an empty <code>TransferData</code> object that will be filled in on return
   *     with the platform specific format of the data
   * @see Transfer#nativeToJava
   */
  public void javaToNative(Object object, TransferData transferData) {
    if (!checkImage(object) || !isSupportedType(transferData)) {
      DND.error(DND.ERROR_INVALID_DATA);
    }
    if (OS.GTK_VERSION < OS.VERSION(2, 4, 0)) return;

    ImageData imgData = (ImageData) object;
    if (imgData == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
    Image image = new Image(Display.getCurrent(), imgData);
    long /*int*/ pixbuf = ImageList.createPixbuf(image);
    if (pixbuf != 0) {
      String typeStr = "";
      if (transferData.type == JPEG_ID) typeStr = "jpeg";
      else if (transferData.type == PNG_ID) typeStr = "png";
      else if (transferData.type == BMP_ID) typeStr = "bmp";
      else if (transferData.type == EPS_ID) typeStr = "eps";
      else if (transferData.type == PCX_ID) typeStr = "pcx";
      else if (transferData.type == PPM_ID) typeStr = "ppm";
      else if (transferData.type == RGB_ID) typeStr = "rgb";
      else if (transferData.type == TGA_ID) typeStr = "tga";
      else if (transferData.type == XBM_ID) typeStr = "xbm";
      else if (transferData.type == XPM_ID) typeStr = "xpm";
      else if (transferData.type == XV_ID) typeStr = "xv";
      byte[] type = Converter.wcsToMbcs(null, typeStr, true);
      long /*int*/[] buffer = new long /*int*/[1];
      long /*int*/[] len = new long /*int*/[1];
      if (type == null) return;
      OS.gdk_pixbuf_save_to_bufferv(pixbuf, buffer, len, type, null, null, null);
      OS.g_object_unref(pixbuf);
      transferData.pValue = buffer[0];
      transferData.length = (int) (len[0] + 3) / 4 * 4;
      transferData.result = 1;
      transferData.format = 32;
    }
    image.dispose();
  }