It is a problem that SynthArrowButton created by SynthComboBoxUI is able to gain a focus and behaves partly like a separate component.

Problem from the user's point of view:

0) run the following code snippet
1) press Alt+t
2) press down arrow key and choose some item
3) Press Enter

--> only Button (SynthComboBoxUI) blinks and combobox remains open. So user is not able to use keyboard in combination with labelFor to choose an item from the JComboBox.

Or just attach a FocusListener to the 'c' combobox, run the snippet and just keep pressing TAB. Nothing happend under Metal L&F which is right but which is not the case with GTK L&F since focus is traversed between SynthArrowButton and JComboBox components (which should behave as one component).


public static void main(String[] args) throws Exception {
    UIManager.setLookAndFeel("com.sun.java.swing.plaf.gtk.GTKLookAndFeel");
    SwingUtilities.invokeLater(new Runnable() {
        public void run() {
            JFrame f = new JFrame();
            f.setLayout(new FlowLayout());
            f.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
            JComboBox c = new JComboBox();
            c.addItem("Test 1");
            c.addItem("Test 2");
            c.addItem("Test 3");
            JLabel l = new JLabel("Test: ");
            l.setDisplayedMnemonic('T');
            l.setLabelFor(c);
            f.add(l);
            f.add(c);
            f.pack();
            f.setVisible(true);
        }
    });
}