sclass BackgroundProcessesUI is IBackgroundProcesses {

  Set<Entry> processes = setWithNotify(syncLinkedHashSet(), l0 updateCount);

  SimpleLiveValue<Int> lvCount = new SimpleLiveValue<Int>(Int, 0);

  record Entry(S name) is IBackgroundProcess {

    settable JMenuItem menuItem;

    settable Runnable interruptAction;

    toString { ret name; }

    close { processes.remove(this); }

  }

  JLabel shortLabel() {

    var lbl = bindToolTipToTransformedLiveValue(

      n -> makeToolTip(), lvCount,

        simpleTransformedLiveValueLabel(n -> n2(n), lvCount));

    onMouseDown_anyButton(lbl, e -> {

      var l = cloneList(processes);

      // make sure title is displayed fully

      JPopupMenu menu = new;/* {

        public Dimension getMinimumSize() {

          TitledBorder border = optCast TitledBorder(getBorder());

          _print(+border);

          ret maxDimension(super.getMinimumSize(), border?.getMinimumSize(this));

        }

      };*/

      int n = componentCount(menu);

      for (Entry a : l)

        addMenuItem(menu, processToMenuItem(a));

      if (componentCount(menu) != n) {

        var border = jRaisedSectionBorder("Background Processes");

        setBorder(menu, border);

        showPopupMenu(menu, e);

        var size = menu.getSize();

        var borderSize = dimensionPlus(10 /* hack */, 0, border.getMinimumSize(menu));

        printVars(+size, +borderSize);

        menu.setPopupSize(maxDimension(size, borderSize));

      }

    });

    ret lbl;

  }

  void add(Entry process) {

    processes.add(process);

  }

  void remove(Entry process) {

    processes.remove(process);

  }

  void addOrRemove(bool add, Entry process) {

    if (add) add(process); else remove(process);

  }

  public Entry tempAdd(S name) {

    ret tempAdd(new Entry(or2(name, "Unnamed process")));

  }

  public Entry tempAdd(Entry process) {

    if (process == null) null;

    processes.add(process);

    ret process;

  }

  void updateCount {

    lvCount.set(l(processes));

  }

  S makeToolTip() {

    var l = listProcesses();

    ret empty(l) ? "No background processes"

      : n2(l, "background process", "background processes")

      + ": " + joinWithComma(processes);

  }

  swappable JMenuItem processToMenuItem(Entry process) {

    try object process.getMenuItem();

    if (process.interruptAction() != null)

      ret jMenuItem("Interrupt " + process, rThread(process.interruptAction()));

    ret jMenuItem(process + " [no action available]");

  }

  L<Entry> listProcesses() { ret cloneList(processes); }

  Cl<Entry> processesNamedIC(S name) {

    ret filter(listProcesses(), entry -> eqic(entry.name, name));

  }

}