code: //==============================================================================
  //	
  //	Copyright (c) 2002-
  //	Authors:
  //	* Andrew Hinton <ug60axh@cs.bham.ac.uk> (University of Birmingham)
  //	* Dave Parker <david.parker@comlab.ox.ac.uk> (University of Oxford, formerly University of Birmingham)
  //	
  //------------------------------------------------------------------------------
  //	
  //	This file is part of PRISM.
  //	
  //	PRISM is free software; you can redistribute it and/or modify
  //	it under the terms of the GNU General Public License as published by
  //	the Free Software Foundation; either version 2 of the License, or
  //	(at your option) any later version.
  //	
  //	PRISM is distributed in the hope that it will be useful,
  //	but WITHOUT ANY WARRANTY; without even the implied warranty of
  //	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  //	GNU General Public License for more details.
  //	
  //	You should have received a copy of the GNU General Public License
  //	along with PRISM; if not, write to the Free Software Foundation,
  //	Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  //	
  //==============================================================================
  
  package userinterface.util;
  
  import java.awt.Color;
  import java.awt.Component;
  import java.awt.Insets;
  
  import javax.swing.JTable;
  import javax.swing.JTextArea;
  import javax.swing.UIManager;
  import javax.swing.border.EmptyBorder;
  
  import prism.Prism;
  import prism.PrismLangException;
  
  /**
   * This does not store an expression, it actually maintains a string which is
   * tested for its validity with the PRISM parser
   */
  public class ExpressionProperty extends SingleProperty
  {
  
  	protected Prism pr;
  
  	private boolean valid;
  
  	/** Creates a new instance of ExpressionProperty */
  	public ExpressionProperty(PropertyOwner owner, String name, String value, Prism pr)
  	{
  		this(owner, name, value, "", pr);
  	}
  
  	public ExpressionProperty(PropertyOwner owner, String name, String value, String comment, Prism pr)
  	{
  		super(owner, name, "", "", true, comment);
  		this.pr = pr;
  		valid = true;
  		area = new JTextArea();
  		area.setLineWrap(false);
  		area.setOpaque(true);
  		try {
  			setProperty(value);
  		} catch (Exception e) {
  		}
  	}
  
  	public String getExpression()
  	{
  		return (String) getProperty();
  	}
  
  	public void setProperty(Object property) throws PropertyException
  	{
  		String expression = property.toString();
  		try {
  			if (pr == null)
  				throw new PrismLangException("");
  			if (!expression.equals("")) {
  				Prism.parseSingleExpressionString(expression);
  			}
  			valid = true;
  		} catch (PrismLangException e) {
  			valid = false;
  		}
  		super.setProperty(property);
  	}
  
  	public void setEnabled(boolean enabled)
  	{
  		super.setEnabled(enabled);
  
  		if (area != null)
  			area.setEnabled(enabled);
  	}
  
  	JTextArea area;
  
  	public Component getTableCellRendererComponent(JTable table, Object value, boolean isSelected, boolean hasFocus, int row, int column)
  	{
  		////System.out.println("rendering "+value.toString());
  		if (isSelected) {
  			area.setForeground(table.getSelectionForeground());
  			area.setBackground(table.getSelectionBackground());
  		} else {
  			area.setForeground(table.getForeground());
  			area.setBackground(table.getBackground());
  		}
  
  		area.setFont(table.getFont());
  
  		if (hasFocus) {
  			area.setBorder(UIManager.getBorder("Table.focusCellHighlightBorder"));
  			if (table.isCellEditable(row, column)) {
  				area.setForeground(UIManager.getColor("Table.focusCellForeground"));
  				area.setBackground(UIManager.getColor("Table.focusCellBackground"));
  			}
  		} else {
  			area.setBorder(new EmptyBorder(0, 2, 2, 1));
  		}
  		//area.setBackground( Color.yellow);
  		area.setMargin(new Insets(0, 2, 4, 2));
  		area.setText((value == null) ? "" : toString());
  
  		if (!valid) {
  			area.setForeground(Color.red);
  
  		}
  		return area;
  	}
  }
  