1 /*
2 * Copyright (c) 2005, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25 package javax.swing;
26
27 import java.awt.Graphics2D;
28
29 /**
30 * <p>A painting delegate. The Painter interface defines exactly one method,
31 * <code>paint</code>. It is used in situations where the developer can change
32 * the painting routine of a component without having to resort to subclassing
33 * the component. It is also generically useful when doing any form of painting
34 * delegation.</p>
35 *
36 * <p><code>Painter</code>s are simply encapsulations of Java2D code and make
37 * it fairly trivial to reuse existing <code>Painter</code>s or to combine
38 * them together. Implementations of this interface are also trivial to write,
39 * such that if you can't find a <code>Painter</code> that does what you need,
40 * you can write one with minimal effort. Writing a <code>Painter</code> requires
41 * knowledge of Java2D.</p>
42 *
43 * <p>A <code>Painter</code> may be created with a type parameter. This type will be
44 * expected in the <code>paint</code> method. For example, you may wish to write a
45 * <code>Painter</code> that only works with subclasses of {@link java.awt.Component}.
46 * In that case, when the <code>Painter</code> is declared, you may declare that
47 * it requires a <code>Component</code>, allowing the paint method to be type safe. Ex:
48 * <pre>
49 * {@code
50 * Painter<Component> p = new Painter<Component>() {
51 * public void paint(Graphics2D g, Component c, int width, int height) {
52 * g.setColor(c.getBackground());
53 * //and so forth
54 * }
55 * }
56 * }
57 * </pre>
58 *
59 * <p>This interface makes no guarantees of threadsafety.</p>
60 *
61 * @author rbair
62 */
63 public interface Painter<T> {
64 /**
65 * <p>Renders to the given {@link java.awt.Graphics2D} object. Implementations
66 * of this method <em>may</em> modify state on the <code>Graphics2D</code>, and are not
67 * required to restore that state upon completion. In most cases, it is recommended
68 * that the caller pass in a scratch graphics object. The <code>Graphics2D</code>
69 * must never be null.</p>
70 *
71 * <p>State on the graphics object may be honored by the <code>paint</code> method,
72 * but may not be. For instance, setting the antialiasing rendering hint on the
73 * graphics may or may not be respected by the <code>Painter</code> implementation.</p>
74 *
75 * <p>The supplied object parameter acts as an optional configuration argument.
76 * For example, it could be of type <code>Component</code>. A <code>Painter</code>
77 * that expected it could then read state from that <code>Component</code> and
78 * use the state for painting. For example, an implementation may read the
79 * backgroundColor and use that.</p>
80 *
81 * <p>Generally, to enhance reusability, most standard <code>Painter</code>s ignore
82 * this parameter. They can thus be reused in any context. The <code>object</code>
83 * may be null. Implementations must not throw a NullPointerException if the object
84 * parameter is null.</p>
85 *
86 * <p>Finally, the <code>width</code> and <code>height</code> arguments specify the
87 * width and height that the <code>Painter</code> should paint into. More
88 * specifically, the specified width and height instruct the painter that it should
89 * paint fully within this width and height. Any specified clip on the
90 * <code>g</code> param will further constrain the region.</p>
91 *
92 * <p>For example, suppose I have a <code>Painter</code> implementation that draws
93 * a gradient. The gradient goes from white to black. It "stretches" to fill the
94 * painted region. Thus, if I use this <code>Painter</code> to paint a 500 x 500
95 * region, the far left would be black, the far right would be white, and a smooth
96 * gradient would be painted between. I could then, without modification, reuse the
97 * <code>Painter</code> to paint a region that is 20x20 in size. This region would
98 * also be black on the left, white on the right, and a smooth gradient painted
99 * between.</p>
100 *
101 * @param g The Graphics2D to render to. This must not be null.
102 * @param object an optional configuration parameter. This may be null.
103 * @param width width of the area to paint.
104 * @param height height of the area to paint.
105 */
106 public void paint(Graphics2D g, T object, int width, int height);
107 }