public void addCollapseButton(Runnable handler) {
    JComponent component = getEditorComponent();
    if (component instanceof EditorTextField) {
      ((EditorTextField)component).addSettingsProvider(editor -> {
        editor.getContentComponent().putClientProperty(Expandable.class, new Expandable() {
          @Override
          public void expand() {
          }

          @Override
          public void collapse() {
            handler.run();
          }

          @Override
          public boolean isExpanded() {
            return true;
          }
        });
        addCollapseButton(editor, handler);
      });
    }
  }
public void addCollapseButton(Runnable handler)