public void actionPerformed(ActionEvent e) {
		ConfigurationButton button = null;
		try {
			button = (ConfigurationButton) e.getSource();
		} catch (ClassCastException ex) {
			return; // Then, we don't care.
		}
		Configuration config = button.getConfiguration();
		if (!configurationToButtonMap.containsKey(config))
			return;
		if (button.isSelected())
			selected.add(config);
		else
			selected.remove(config);
		distributeSelectionEvent(new ConfigurationSelectionEvent(this));
	}