Java example source code file (BufferStrategy.java)

This example Java source code file (BufferStrategy.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

awt, buffercapabilities, bufferstrategy, graphics

The BufferStrategy.java Java example source code

/*
 * Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package java.awt.image;

import java.awt.BufferCapabilities;
import java.awt.Graphics;
import java.awt.Image;

/**
 * The <code>BufferStrategy class represents the mechanism with which
 * to organize complex memory on a particular <code>Canvas or
 * <code>Window.  Hardware and software limitations determine whether and
 * how a particular buffer strategy can be implemented.  These limitations
 * are detectable through the capabilities of the
 * <code>GraphicsConfiguration used when creating the
 * <code>Canvas or Window.
 * <p>
 * It is worth noting that the terms <i>buffer and surface are meant
 * to be synonymous: an area of contiguous memory, either in video device
 * memory or in system memory.
 * <p>
 * There are several types of complex buffer strategies, including
 * sequential ring buffering and blit buffering.
 * Sequential ring buffering (i.e., double or triple
 * buffering) is the most common; an application draws to a single <i>back
 * buffer</i> and then moves the contents to the front (display) in a single
 * step, either by copying the data or moving the video pointer.
 * Moving the video pointer exchanges the buffers so that the first buffer
 * drawn becomes the <i>front buffer, or what is currently displayed on the
 * device; this is called <i>page flipping.
 * <p>
 * Alternatively, the contents of the back buffer can be copied, or
 * <i>blitted forward in a chain instead of moving the video pointer.
 * <pre>{@code
 * Double buffering:
 *
 *                    ***********         ***********
 *                    *         * ------> *         *
 * [To display] <---- * Front B *   Show  * Back B. * <---- Rendering
 *                    *         * <------ *         *
 *                    ***********         ***********
 *
 * Triple buffering:
 *
 * [To      ***********         ***********        ***********
 * display] *         * --------+---------+------> *         *
 *    <---- * Front B *   Show  * Mid. B. *        * Back B. * <---- Rendering
 *          *         * <------ *         * <----- *         *
 *          ***********         ***********        ***********
 *
 * }</pre>
 * <p>
 * Here is an example of how buffer strategies can be created and used:
 * <pre>
 *
 * // Check the capabilities of the GraphicsConfiguration
 * ...
 *
 * // Create our component
 * Window w = new Window(gc);
 *
 * // Show our window
 * w.setVisible(true);
 *
 * // Create a general double-buffering strategy
 * w.createBufferStrategy(2);
 * BufferStrategy strategy = w.getBufferStrategy();
 *
 * // Main loop
 * while (!done) {
 *     // Prepare for rendering the next frame
 *     // ...
 *
 *     // Render single frame
 *     do {
 *         // The following loop ensures that the contents of the drawing buffer
 *         // are consistent in case the underlying surface was recreated
 *         do {
 *             // Get a new graphics context every time through the loop
 *             // to make sure the strategy is validated
 *             Graphics graphics = strategy.getDrawGraphics();
 *
 *             // Render to graphics
 *             // ...
 *
 *             // Dispose the graphics
 *             graphics.dispose();
 *
 *             // Repeat the rendering if the drawing buffer contents
 *             // were restored
 *         } while (strategy.contentsRestored());
 *
 *         // Display the buffer
 *         strategy.show();
 *
 *         // Repeat the rendering if the drawing buffer was lost
 *     } while (strategy.contentsLost());
 * }
 *
 * // Dispose the window
 * w.setVisible(false);
 * w.dispose();
 * </code>

* * @see java.awt.Window * @see java.awt.Canvas * @see java.awt.GraphicsConfiguration * @see VolatileImage * @author Michael Martak * @since 1.4 */ public abstract class BufferStrategy { /** * Returns the <code>BufferCapabilities for this * <code>BufferStrategy. * * @return the buffering capabilities of this strategy */ public abstract BufferCapabilities getCapabilities(); /** * Creates a graphics context for the drawing buffer. This method may not * be synchronized for performance reasons; use of this method by multiple * threads should be handled at the application level. Disposal of the * graphics object obtained must be handled by the application. * * @return a graphics context for the drawing buffer */ public abstract Graphics getDrawGraphics(); /** * Returns whether the drawing buffer was lost since the last call to * <code>getDrawGraphics. Since the buffers in a buffer strategy * are usually type <code>VolatileImage, they may become lost. * For a discussion on lost buffers, see <code>VolatileImage. * * @return Whether or not the drawing buffer was lost since the last call * to <code>getDrawGraphics. * @see java.awt.image.VolatileImage */ public abstract boolean contentsLost(); /** * Returns whether the drawing buffer was recently restored from a lost * state and reinitialized to the default background color (white). * Since the buffers in a buffer strategy are usually type * <code>VolatileImage, they may become lost. If a surface has * been recently restored from a lost state since the last call to * <code>getDrawGraphics, it may require repainting. * For a discussion on lost buffers, see <code>VolatileImage. * * @return Whether or not the drawing buffer was restored since the last * call to <code>getDrawGraphics. * @see java.awt.image.VolatileImage */ public abstract boolean contentsRestored(); /** * Makes the next available buffer visible by either copying the memory * (blitting) or changing the display pointer (flipping). */ public abstract void show(); /** * Releases system resources currently consumed by this * <code>BufferStrategy and * removes it from the associated Component. After invoking this * method, <code>getBufferStrategy will return null. Trying * to use a <code>BufferStrategy after it has been disposed will * result in undefined behavior. * * @see java.awt.Window#createBufferStrategy * @see java.awt.Canvas#createBufferStrategy * @see java.awt.Window#getBufferStrategy * @see java.awt.Canvas#getBufferStrategy * @since 1.6 */ public void dispose() { } }