sclass CollapsibleLeftPanel > MetaWithChangeListeners is Swingable {
  settableWithVar volatile S sidePanelName;
  JComponent sideComponent, mainComponent;
  JSplitPane splitPane;
  settableWithVar volatile bool expanded;
  SingleComponentPanel scp = singleComponentPanel();
  
  *(bool *expanded, S *sidePanelName, JComponent *sideComponent, JComponent *mainComponent) {
  }
  
  void expand {
    if (scaffolding()) print("CollapsibleLeftPanel.expand");
    setExpanded(true);
  }
  
  void collapse { setExpanded(false); }
  
  scaffolded void updateScp() swing {
    if (expanded) {
      splitPane().setRightComponent(jMinWidth0(mainComponent));
      scp.set(splitPane());
    } else {
      splitPane().setRightComponent(jMinWidth0(jpanel()));
      scp.set(westAndCenterWithMargin(
        sidePanelMargins(vstack(expandButton())), mainComponent));
    }
  }
  
  JComponent expandButton() {
    ret jClickableImage_instantToolTip(#1103075, "Expand " + sidePanelName, r expand);
  }
  
  JComponent collapseButton() {
    ret jClickableImage_instantToolTip(#1103076, "Collapse " + sidePanelName, r collapse);
  }
  
  JComponent wrappedSideComponent() {
    ret sidePanelMargins(northAndCenterWithMargin(
      westAndCenterWithMargin(collapseButton(), liveValueLabel(varSidePanelName())),
      sideComponent
    ));
  }

  JSplitPane splitPane() {
    if (scaffolding()) print("splitPane " + splitPane);
    if (splitPane == null) {
      splitPane = jhsplit_minZero(0.25, wrappedSideComponent(), null);
      varExpanded().onChangeAndNow(r updateScp);
    }
    ret splitPane;
  }
  
  swappable JComponent sidePanelMargins(JComponent c) { ret c; }
  
  visualize {
    splitPane();
    ret scp;
  }
}