001 /*
002 * $Id: Painter.java 2124 2007-07-16 13:55:44Z kschaefe $
003 *
004 * Copyright 2006 Sun Microsystems, Inc., 4150 Network Circle,
005 * Santa Clara, California 95054, U.S.A. All rights reserved.
006 *
007 * This library is free software; you can redistribute it and/or
008 * modify it under the terms of the GNU Lesser General Public
009 * License as published by the Free Software Foundation; either
010 * version 2.1 of the License, or (at your option) any later version.
011 *
012 * This library is distributed in the hope that it will be useful,
013 * but WITHOUT ANY WARRANTY; without even the implied warranty of
014 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
015 * Lesser General Public License for more details.
016 *
017 * You should have received a copy of the GNU Lesser General Public
018 * License along with this library; if not, write to the Free Software
019 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
020 */
021
022 package org.jdesktop.swingx.painter;
023
024 import java.awt.Graphics2D;
025
026 /**
027 * <p>A painting delegate. The Painter interface defines exactly one method,
028 * <code>paint</code>. It is used in situations where the developer can change
029 * the painting routine of a component without having to resort to subclassing
030 * the component.</p>
031 *
032 * <p><code>Painter</code>s are simply encapsulations of Java2D code and make
033 * it fairly trivial to reuse existing <code>Painter</code>s or to combine
034 * them together. Implementations of this interface are also trivial to write,
035 * such that if you can't find a <code>Painter</code> that does what you need,
036 * you can write one with minimal effort. Writing a <code>Painter</code> requires
037 * knowledge of Java2D.</p>
038 *
039 * <p>A <code>Painter</code> may be created with a type parameter. This type will be
040 * expected in the <code>paint</code> method. For example, you may wish to write a
041 * <code>Painter</code> that only works with subclasses of {@link java.awt.Component}.
042 * In that case, when the <code>Painter</code> is declared, you may declare that
043 * it requires a <code>Component</code>, allowing the paint method to be type safe. Ex:
044 * <pre><code>
045 * Painter<Component> p = new Painter<Component>() {
046 * public void paint(Graphics2D g, Component c, int width, int height) {
047 * g.setColor(c.getBackground());
048 * //and so forth
049 * }
050 * }
051 * </code></pre></p>
052 *
053 * <p>This class is <strong>not</strong> threadsafe.</p>
054 *
055 * @author rbair
056 * @see AbstractPainter
057 * @see CompoundPainter
058 * @see org.jdesktop.swingx.JXPanel
059 * @see org.jdesktop.swingx.JXLabel
060 * @see org.jdesktop.swingx.JXButton
061 */
062 public interface Painter<T> {
063 /**
064 * <p>Renders to the given {@link java.awt.Graphics2D} object. Implementations
065 * of this method <em>may</em> modify state on the <code>Graphics2D</code>, and are not
066 * required to restore that state upon completion. In most cases, it is recommended
067 * that the caller pass in a scratch graphics object. The <code>Graphics2D</code>
068 * must never be null.</p>
069 *
070 * <p>State on the graphics object may be honored by the <code>paint</code> method,
071 * but may not be. For instance, setting the antialiasing rendering hint on the
072 * graphics may or may not be respected by the <code>Painter</code> implementation.</p>
073 *
074 * <p>The supplied object parameter acts as an optional configuration argument.
075 * For example, it could be of type <code>Component</code>. A <code>Painter</code>
076 * that expected it could then read state from that <code>Component</code> and
077 * use the state for painting. For example, an implementation may read the
078 * backgroundColor and use that.</p>
079 *
080 * <p>Generally, to enhance reusability, most standard <code>Painter</code>s ignore
081 * this parameter. They can thus be reused in any context. The <code>object</code>
082 * may be null. Implementations must not throw a NullPointerException if the object
083 * parameter is null.</p>
084 *
085 * <p>Finally, the <code>width</code> and <code>height</code> arguments specify the
086 * width and height that the <code>Painter</code> should paint into. More
087 * specifically, the specified width and height instruct the painter that it should
088 * paint fully within this width and height. Any specified clip on the
089 * <code>g</code> param will further constrain the region.</p>
090 *
091 * <p>For example, suppose I have a <code>Painter</code> implementation that draws
092 * a gradient. The gradient goes from white to black. It "stretches" to fill the
093 * painted region. Thus, if I use this <code>Painter</code> to paint a 500 x 500
094 * region, the far left would be black, the far right would be white, and a smooth
095 * gradient would be painted between. I could then, without modification, reuse the
096 * <code>Painter</code> to paint a region that is 20x20 in size. This region would
097 * also be black on the left, white on the right, and a smooth gradient painted
098 * between.</p>
099 *
100 * @param g The Graphics2D to render to. This must not be null.
101 * @param object an optional configuration parameter. This may be null.
102 * @param width width of the area to paint.
103 * @param height height of the area to paint.
104 */
105 public void paint(Graphics2D g, T object, int width, int height);
106 }