Popup containing a JPanel with a JComboBox

Question

I like to get a Popup containing a JPanel with a JComboBox and some other stuff.
There are two difficulties:
- it is not possible to use a Combobox with a light weight popup. So I set combobox.LightWeightPopupEnabled(false). Otherwise the combobox popup won't be shown.
- If the user changes the popups size (see code: this.getSize() returns a different dimension because of a new Frame size). The combobox popups won't be shown proper after a while.
Does someone know, why it is not possible to use comboboxes with light weight popups?
Does somebody know, how to fix the size problem?
I am using JDK 1.4.1 for Windows Systems.
  private Popup getPopup(){
    if (popup != null) {
      hidePopup();
    Point p = this.getLocationOnScreen();
    Dimension inputSize = this.getSize();
    Dimension tableSize = tablePopup.getSize();
    if( ( p.y + tableSize.height ) < screenSize.height) {
      // will fit below input panel
      popup = factory.getPopup( this, tablePopup,
                                p.x, p.y + (int)inputSize.height );
    } else {
      // need to fit it above input panel
      popup = factory.getPopup( this, tablePopup,
                                p.x, p.y - (int)tableSize.height );
    return popup;

Answer 1

Ok, it works proper with Windows L&F. So I replaced
private PopupFactory factory =  PopupFactory.getSharedInstance();by
private WindowsPopupFactory factory = new WindowsPopupFactory();