sclass JFileDropTarget is Swingable {
  settable S msg = "Drop file here";
  
  // currently dropped file
  settable File file;
  
  SingleComponentPanel scp = scp();
  
  cachedVisualize {
    if (!scp.hasComponent())
      scp.setComponent(makeComponent());
  }
  
  JComponent makeComponent() {
    ret file == null
      ? noFileComponent()
      : componentForFile(msg);
  }
  
  JComponent noFileComponent() {
    ret jcenteredlabel(msg);
  }
  
  swappable JComponent componentForFile(File file) {
    ret jfullcenter(jFilePathLabel(file));
  }
}