code: protected void onUp(Event event) {
  
          m_clientX = event.getClientX();
          m_clientY = event.getClientY();
          m_modifierCTRL = event.getCtrlKey() || event.getMetaKey();
          if ((m_currentTarget == null) || (m_currentTarget.getPlaceholderIndex() < 0)) {
              cancel();
          } else {
              drop();
          }
      }
docs: Executed on mouse up while dragging.<p>
  
  @param event the event