/*
* $Id$
*
* Copyright 2006 Sun Microsystems, Inc., 4150 Network Circle,
* Santa Clara, California 95054, U.S.A. All rights reserved.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
package org.jdesktop.swingx.painter;
import java.awt.Graphics2D;
/**
* <p>A painting delegate. The Painter interface defines exactly one method,
* <code>paint</code>. It is used in situations where the developer can change
* the painting routine of a component without having to resort to subclassing
* the component.</p>
*
* <p><code>Painter</code>s are simply encapsulations of Java2D code and make
* it fairly trivial to reuse existing <code>Painter</code>s or to combine
* them together. Implementations of this interface are also trivial to write,
* such that if you can't find a <code>Painter</code> that does what you need,
* you can write one with minimal effort. Writing a <code>Painter</code> requires
* knowledge of Java2D.</p>
*
* <p>A <code>Painter</code> may be created with a type parameter. This type will be
* expected in the <code>paint</code> method. For example, you may wish to write a
* <code>Painter</code> that only works with subclasses of {@link java.awt.Component}.
* In that case, when the <code>Painter</code> is declared, you may declare that
* it requires a <code>Component</code>, allowing the paint method to be type safe. Ex:
* <pre><code>
* Painter<Component> p = new Painter<Component>() {
* public void paint(Graphics2D g, Component c, int width, int height) {
* g.setColor(c.getBackground());
* //and so forth
* }
* }
* </code></pre></p>
*
* <p>This class is <strong>not</strong> threadsafe.</p>
*
* @author rbair
* @see AbstractPainter
* @see CompoundPainter
*/
public interface Painter<T> {
/**
* <p>Renders to the given {@link java.awt.Graphics2D} object. Implementations
* of this method <em>may</em> modify state on the <code>Graphics2D</code>, and are not
* required to restore that state upon completion. In most cases, it is recommended
* that the caller pass in a scratch graphics object. The <code>Graphics2D</code>
* must never be null.</p>
*
* <p>State on the graphics object may be honored by the <code>paint</code> method,
* but may not be. For instance, setting the antialiasing rendering hint on the
* graphics may or may not be respected by the <code>Painter</code> implementation.</p>
*
* <p>The supplied object parameter acts as an optional configuration argument.
* For example, it could be of type <code>Component</code>. A <code>Painter</code>
* that expected it could then read state from that <code>Component</code> and
* use the state for painting. For example, an implementation may read the
* backgroundColor and use that.</p>
*
* <p>Generally, to enhance reusability, most standard <code>Painter</code>s ignore
* this parameter. They can thus be reused in any context. The <code>object</code>
* may be null. Implementations must not throw a NullPointerException if the object
* parameter is null.</p>
*
* <p>Finally, the <code>width</code> and <code>height</code> arguments specify the
* width and height that the <code>Painter</code> should paint into. More
* specifically, the specified width and height instruct the painter that it should
* paint fully within this width and height. Any specified clip on the
* <code>g</code> param will further constrain the region.</p>
*
* <p>For example, suppose I have a <code>Painter</code> implementation that draws
* a gradient. The gradient goes from white to black. It "stretches" to fill the
* painted region. Thus, if I use this <code>Painter</code> to paint a 500 x 500
* region, the far left would be black, the far right would be white, and a smooth
* gradient would be painted between. I could then, without modification, reuse the
* <code>Painter</code> to paint a region that is 20x20 in size. This region would
* also be black on the left, white on the right, and a smooth gradient painted
* between.</p>
*
* @param g The Graphics2D to render to. This must not be null.
* @param object an optional configuration parameter. This may be null.
* @param width width of the area to paint.
* @param height height of the area to paint.
*/
public void paint(Graphics2D g, T object, int width, int height);
}