sclass CollapsibleLeftPanel is Swingable {
  S sidePanelName;
  JComponent sideComponent;
  JSplitPane splitPane;
  bool collapsed;
  SingleComponentPanel spcSide = singleComponentPanel();
  
  *(S *sidePanelName, JComponent *sideComponent, JComponent mainComponent,
    bool *collapsed) {
    updateScpSide();
    splitPane = jhsplit(0.25, scpSide, mainComponent);
  }
  
  void setCollapsed(bool collapsed) {
    if (this.collapsed != collapsed) {
      this.collapsed = collapsed;
      updateScpSide();
    }
  }
  
  void updateScpSide {
    scpSide.set(collapsed ? collapsedComponent()
      : wrappedSideComponent());
  }
  
  visual splitPane;
}