| /* |
| * Copyright (c) 2000, 2007, 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</code> class represents the mechanism with which |
| * to organize complex memory on a particular <code>Canvas</code> or |
| * <code>Window</code>. Hardware and software limitations determine whether and |
| * how a particular buffer strategy can be implemented. These limitations |
| * are detectible through the capabilities of the |
| * <code>GraphicsConfiguration</code> used when creating the |
| * <code>Canvas</code> or <code>Window</code>. |
| * <p> |
| * It is worth noting that the terms <i>buffer</i> and <i>surface</i> 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</i>, or what is currently displayed on the |
| * device; this is called <i>page flipping</i>. |
| * <p> |
| * Alternatively, the contents of the back buffer can be copied, or |
| * <i>blitted</i> forward in a chain instead of moving the video pointer. |
| * <p> |
| * <pre> |
| * 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><code> |
| * |
| * // 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></pre> |
| * |
| * @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</code> for this |
| * <code>BufferStrategy</code>. |
| * |
| * @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</code>. Since the buffers in a buffer strategy |
| * are usually type <code>VolatileImage</code>, they may become lost. |
| * For a discussion on lost buffers, see <code>VolatileImage</code>. |
| * |
| * @return Whether or not the drawing buffer was lost since the last call |
| * to <code>getDrawGraphics</code>. |
| * @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</code>, they may become lost. If a surface has |
| * been recently restored from a lost state since the last call to |
| * <code>getDrawGraphics</code>, it may require repainting. |
| * For a discussion on lost buffers, see <code>VolatileImage</code>. |
| * |
| * @return Whether or not the drawing buffer was restored since the last |
| * call to <code>getDrawGraphics</code>. |
| * @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</code> and |
| * removes it from the associated Component. After invoking this |
| * method, <code>getBufferStrategy</code> will return null. Trying |
| * to use a <code>BufferStrategy</code> 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() { |
| } |
| } |
