Swing Popup menus are not completely painted

I have this in several areas of an app I'm working on and I can see no way to replicate it outside of this app. I can't create a sscce since I can't manage to replicate this at all - This leads me to believe that it must be something caused by the parent frame / app, but I have no idea where to look.

What I see is that part of the left hand side of popup menus are not painted. I see this behaviour with JCombobox popups as well as JPopupMenu's. I've attached a couple of images to show what I mean. most of these did work properly previously and without any changes to the code where the popupmenu's are created or displayed, this problem has spread to a lot of other places now.

I'm not mixing heavyweight and lightweight components, as we only use Swing components and the two examples I show below are in completely different parts of the app. The first one is in a fairly simple panel with very little functionality, but the second example (JPoopupMenu) is in a very complex legacy panel.

On both of these and other place where I see it, I'm not altering the parent's clipping region at all and in all case, these popups are constructed and displayed on the EDT.

I know this question is rather vague, but that is because of the nature of the problem. I'll provide any requested info.

This specific case happens to be a custom combobox model, but we've seen it when using the DefaultComboBoxModel as well:

public class GroupListModel extends AbstractListModel
    implements ComboBoxModel{

private List<groupObject> groups;
private groupObject selectedItem = null;

public GroupListModel() {
    this(new ArrayList<groupObject>());
}

public GroupListModel(List<groupObject> groups) {
    this.groups = groups;
}

@Override
public int getSize() {
    return groups.size();
}

@Override
public Object getElementAt(int index) {
    if(index>=groups.size()){
        throw new IndexOutOfBoundsException();
    }
    return groups.get(index);
}

public void setGroups(List<groupObject> groups){
    this.groups = groups;
    fireContentsChanged(this, 0, groups.size());
}

public void addElement(groupObject group){
开发者_开发问答    groups.add(group);
    fireIntervalAdded(this, groups.size()-1, groups.size()-1);
}

public void addElement(groupObject group, int index){
    groups.add(index, group);
    fireIntervalAdded(this, index, index+1);
}

@Override
public void setSelectedItem(Object anItem) {
    if(anItem instanceof groupObject){
        selectedItem = (groupObject) anItem;
    }else{
        throw new IllegalArgumentException();
    }
    fireContentsChanged(this, 0, groups.size());
}

@Override
public Object getSelectedItem() {
    return selectedItem;
}

This is a JPopupMenu that gets displayed when you right click using the following code:

public void mouseClicked(MouseEvent e) {
                            if( e.getButton()==e.BUTTON3 ){
                                lastClickedID = tmp.getUniqueID();
                                lastClickedGui = (bigEventGui) gui;
                                itmComplete.setText(
                                        completed ?
                                            ctOne.getLang("uncomplete") :
                                            ctOne.getLang("complete") );
                                itmComplete.setIcon( (completed ?
                                    iconFramework.getIcon(
                                        iconFramework.UNCOMPLETE_ITEM,
                                        24, false) :
                                    iconFramework.getIcon(
                                        iconFramework.COMPLETE_ITEM,
                                        24, false) ));
                                popRCEvent.show(gui, e.getX(), e.getY() );
                            }

---

Taking out JPopupMenu.setDefaultLightWeightPopupEnabled(false); fixed it... Can somebody please try and explain why?