XMouseDragGestureRecognizer.java 文件源码

/**
 * determine the drop action from the event
 */

protected int mapDragOperationFromModifiers(MouseEvent e) {
    int mods = e.getModifiersEx();
    int btns = mods & ButtonMask;

    // Do not allow right mouse button drag since Motif DnD does not
    // terminate drag operation on right mouse button release.
    if (!(btns == InputEvent.BUTTON1_DOWN_MASK ||
          btns == InputEvent.BUTTON2_DOWN_MASK)) {
        return DnDConstants.ACTION_NONE;
    }

    return
        SunDragSourceContextPeer.convertModifiersToDropAction(mods,
                                                              getSourceActions());
}