sbool AutoComboBox3_handleTab = true;

sclass AutoComboBox3 extends JComboBox<S> {
  F1<S, Collection<S>> entryMaker; // called (serially) in non-AWT thread
  ReliableSingleThread rst = new(r { update2() });
  S textBehindModel;
  
  *() { this(null); }
  
  *(F1<S, Collection<S>> *entryMaker) {
    setSelectedIndex(-1);
    setEditable(true);
    JTextField text = cast this.getEditor().getEditorComponent();
    text.setFocusable(true);

    text.addKeyListener(new KeyAdapter {
      public void /*keyPressed*/keyReleased(KeyEvent key) {
        if (key.getKeyCode() == KeyEvent.VK_ENTER) ret;
        
        if (key.getKeyCode() == KeyEvent.VK_ESCAPE) { hidePopup(); ret; }
        
        if (AutoComboBox3_handleTab && key.getKeyCode() == KeyEvent.VK_TAB /*&& key.getModifiers() == 0*/) {
          //_print("Have tab event (modifiers=" + key.getModifiers() + ")");
          if (key.getModifiers() == 0 && isPopupVisible()) {
            setSelectedIndex(0); // accept item
            hidePopup();
          } else // standard tab behavior
            swing_standardTabBehavior(key);
            
          ret;
        }
        
        JTextField tf = cast getEditor().getEditorComponent();
        if (tf.getCaretPosition() != l(tf.getText())) ret;
    
        update();
      }
    });
      
    if (AutoComboBox3_handleTab)
      text.setFocusTraversalKeysEnabled(false);
  }
  
  Collection<S> getSuggestions(S text) {
    ret callF(entryMaker, text);
  }
  
  JTextField textField() {
    ret (JTextField) getEditor().getEditorComponent();
  }
  
  void update {
    if (neq(getText(textField()), textBehindModel))
      rst.trigger();
  }
  
  bool setTextBehindModel(fS text) {
    ret swing(func -> Bool {
      if (eq(text, textBehindModel)) false;
      textBehindModel = text;
      true;
    });
  }
  
  void update2 {
    fS text = getText(textField());
    if (!setTextBehindModel(text)) ret;
    try {
      final Vector list = new Vector(getSuggestions(text));
      swing {
        if (nempty(list)) {
          S currentText = getText(textField());
          setModel(new DefaultComboBoxModel(list));
          setTextBehindModel(text);
          setSelectedIndex(-1);
          textField().setText(currentText);
          showPopup();
        } else
          hidePopup();
      }
    } catch print e {
      setTextBehindModel(null);
    }
  }
}

Began life as a copy of #1012958