/*
 * @(#)DefaultTableCellRenderer.java	1.25 00/02/02
 *
 * Copyright 1998-2000 Sun Microsystems, Inc. All Rights Reserved.
 * 
 * This software is the proprietary information of Sun Microsystems, Inc.  
 * Use is subject to license terms.
 * 
 */

package javax.swing.table;

import javax.swing.*;
import javax.swing.table.TableCellRenderer;
import javax.swing.border.*;

import java.awt.Component;
import java.awt.Color;
import java.awt.Rectangle;

import java.io.Serializable;


/**
 * The standard class for rendering (displaying) individual cells
 * in a <code>JTable</code>.
 * <p>
 *
 * <strong><a name="override">Implementation Note:</a></strong>
 * This class inherits from <code>JLabel</code>, a standard component class. 
 * However <code>JTable</code> employs a unique mechanism for rendering
 * its cells and therefore requires some slightly modified behavior
 * from its cell renderer.  
 * The table class defines a single cell renderer and uses it as a 
 * as a rubber-stamp for rendering all cells in the table; 
 * it renders the first cell,
 * changes the contents of that cell renderer, 
 * shifts the origin to the new location, re-draws it, and so on.
 * The standard <code>JLabel</code> component was not
 * designed to be used this way and we want to avoid 
 * triggering a <code>revalidate</code> each time the
 * cell is drawn. This would greatly decrease performance because the
 * <code>revalidate</code> message would be
 * passed up the hierarchy of the container to determine whether any other
 * components would be affected.  So this class
 * overrides the <code>validate</code>, <code>revalidate</code>,
 * <code>repaint</code>, and <code>firePropertyChange</code> methods to be 
 * no-ops.  If you write your own renderer,
 * please keep this performance consideration in mind.
 * <p>
 *
 * <strong>Warning:</strong>
 * Serialized objects of this class will not be compatible with
 * future Swing releases.  The current serialization support is appropriate
 * for short term storage or RMI between applications running the same
 * version of Swing.  A future release of Swing will provide support for
 * long term persistence.
 *
 * @version 1.25 02/02/00
 * @author Philip Milne 
 * @see JTable
 */
public class DefaultTableCellRenderer extends JLabel
    implements TableCellRenderer, Serializable
{

    protected static Border noFocusBorder = new EmptyBorder(1, 1, 1, 1); 
    
    // We need a place to store the color the JLabel should be returned 
    // to after its foreground and background colors have been set 
    // to the selection background color. 
    // These ivars will be made protected when their names are finalized. 
    private Color unselectedForeground; 
    private Color unselectedBackground; 

    /**
     * Creates a default table cell renderer.
     */
    public DefaultTableCellRenderer() {
	super();
	setOpaque(true);
        setBorder(noFocusBorder);
    }

    /**
     * Overrides <code>JComponent.setForeground</code> to assign
     * the unselected-foreground color to the specified color.
     * 
     * @param c set the foreground color to this value
     */
    public void setForeground(Color c) {
        super.setForeground(c); 
        unselectedForeground = c; 
    }
    
    /**
     * Overrides <code>JComponent.setForeground</code> to assign
     * the unselected-background color to the specified color.
     *
     * @param c set the background color to this value
     */
    public void setBackground(Color c) {
        super.setBackground(c); 
        unselectedBackground = c; 
    }

    /**
     * Notification from the <code>UIManager</code> that the look and feel
     * [L&F] has changed.
     * Replaces the current UI object with the latest version from the 
     * <code>UIManager</code>.
     *
     * @see JComponent#updateUI
     */
    public void updateUI() {
        super.updateUI(); 
	setForeground(null);
	setBackground(null);
    }
    
    // implements javax.swing.table.TableCellRenderer
    /**
     *
     * Returns the default table cell renderer.
     *
     * @param table  the <code>JTable</code>
     * @param value  the value to assign to the cell at
     *			<code>[row, column]</code>
     * @param isSelected true if cell is selected
     * @param isFocus true if cell has focus
     * @param row  the row of the cell to render
     * @param column the column of the cell to render
     * @return the default table cell renderer
     */
    public Component getTableCellRendererComponent(JTable table, Object value,
                          boolean isSelected, boolean hasFocus, int row, int column) {

	if (isSelected) {
	   super.setForeground(table.getSelectionForeground());
	   super.setBackground(table.getSelectionBackground());
	}
	else {
	    super.setForeground((unselectedForeground != null) ? unselectedForeground 
	                                                       : table.getForeground());
	    super.setBackground((unselectedBackground != null) ? unselectedBackground 
	                                                       : table.getBackground());
	}
	
	setFont(table.getFont());

	if (hasFocus) {
	    setBorder( UIManager.getBorder("Table.focusCellHighlightBorder") );
	    if (table.isCellEditable(row, column)) {
	        super.setForeground( UIManager.getColor("Table.focusCellForeground") );
	        super.setBackground( UIManager.getColor("Table.focusCellBackground") );
	    }
	} else {
	    setBorder(noFocusBorder);
	}

        setValue(value); 

	// ---- begin optimization to avoid painting background ----
	Color back = getBackground();
	boolean colorMatch = (back != null) && ( back.equals(table.getBackground()) ) && table.isOpaque();
        setOpaque(!colorMatch);
	// ---- end optimization to aviod painting background ----

	return this;
    }
    

    /*
     * The following methods are overridden as a performance measure to 
     * to prune code-paths are often called in the case of renders
     * but which we know are unnecessary.  Great care should be taken
     * when writing your own renderer to weigh the benefits and 
     * drawbacks of overriding methods like these.
     */

    /**
     * Overridden for performance reasons.
     * See the <a href="#override">Implementation Note</a> 
     * for more information.
     */
    public void validate() {}

    /**
     * Overridden for performance reasons.
     * See the <a href="#override">Implementation Note</a> 
     * for more information.
     */
    public void revalidate() {}

    /**
     * Overridden for performance reasons.
     * See the <a href="#override">Implementation Note</a> 
     * for more information.
     */
    public void repaint(long tm, int x, int y, int width, int height) {}

    /**
     * Overridden for performance reasons.
     * See the <a href="#override">Implementation Note</a> 
     * for more information.
     */
    public void repaint(Rectangle r) { }

    /**
     * Overridden for performance reasons.
     * See the <a href="#override">Implementation Note</a> 
     * for more information.
     */
    protected void firePropertyChange(String propertyName, Object oldValue, Object newValue) {	
	// Strings get interned...
	if (propertyName=="text") {
	    super.firePropertyChange(propertyName, oldValue, newValue);
	}
    }

    /**
     * Overridden for performance reasons.
     * See the <a href="#override">Implementation Note</a> 
     * for more information.
     */
    public void firePropertyChange(String propertyName, boolean oldValue, boolean newValue) { }


    /**
     * Sets the string for the cell being rendered to <code>value</code>.
     * 
     * @param value  the string value for this cell; if value is
     *		<code>null</code> it sets the text value to an empty string
     * @see JLabel#setText
     * 
     */
    protected void setValue(Object value) {
	setText((value == null) ? "" : value.toString());
    }
	

    /**
     * A subclass of <code>DefaultTableCellRenderer</code> that
     * implements <code>UIResource</code>.
     * <code>DefaultTableCellRenderer</code> doesn't implement
     * <code>UIResource</code>
     * directly so that applications can safely override the
     * <code>cellRenderer</code> property with
     * <code>DefaultTableCellRenderer</code> subclasses.
     * <p>
     * <strong>Warning:</strong>
     * Serialized objects of this class will not be compatible with
     * future Swing releases.  The current serialization support is appropriate
     * for short term storage or RMI between applications running the same
     * version of Swing.  A future release of Swing will provide support for
     * long term persistence.
     */
    public static class UIResource extends DefaultTableCellRenderer 
        implements javax.swing.plaf.UIResource
    {
    }

}