1 /* BufferCapabilities.java -- double-buffering capabilities descriptor 2 Copyright (C) 2002, 2005 Free Software Foundation, Inc. 3 4 This file is part of GNU Classpath. 5 6 GNU Classpath is free software; you can redistribute it and/or modify 7 it under the terms of the GNU General Public License as published by 8 the Free Software Foundation; either version 2, or (at your option) 9 any later version. 10 11 GNU Classpath is distributed in the hope that it will be useful, but 12 WITHOUT ANY WARRANTY; without even the implied warranty of 13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14 General Public License for more details. 15 16 You should have received a copy of the GNU General Public License 17 along with GNU Classpath; see the file COPYING. If not, write to the 18 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 19 02110-1301 USA. 20 21 Linking this library statically or dynamically with other modules is 22 making a combined work based on this library. Thus, the terms and 23 conditions of the GNU General Public License cover the whole 24 combination. 25 26 As a special exception, the copyright holders of this library give you 27 permission to link this library with independent modules to produce an 28 executable, regardless of the license terms of these independent 29 modules, and to copy and distribute the resulting executable under 30 terms of your choice, provided that you also meet, for each linked 31 independent module, the terms and conditions of the license of that 32 module. An independent module is a module which is not derived from 33 or based on this library. If you modify this library, you may extend 34 this exception to your version of the library, but you are not 35 obligated to do so. If you do not wish to do so, delete this 36 exception statement from your version. */ 37 38 39 package java.awt; 40 41 import java.awt.image.BufferStrategy; 42 43 /** 44 * A double-buffering capability descriptor. This class exposes 45 * details about the double-buffering algorithms used by image 46 * buffers. 47 * 48 * BufferCapabilities represents algorithms that involve at least two 49 * buffers but it can also specify so-called "multi-buffer" schemes 50 * involving more than two buffers. This class describes the 51 * capabilities of the front and back buffers as well as the results 52 * of "flipping" -- that is, what happens when an image is transferred 53 * from the back buffer to the front buffer. 54 * 55 * Flipping may or may not be supported or may be supported only in 56 * fullscreen mode. If it is not supported then "blitting" is implied 57 * -- that is, the contents of the back buffer are copied using a fast 58 * block transfer operation from the back buffer to the front buffer. 59 * 60 * The front buffer is the one that is displayed. 61 * 62 * @author Eric Blake (ebb9@email.byu.edu) 63 * 64 * @see BufferStrategy#getCapabilities() 65 * @see GraphicsConfiguration#getBufferCapabilities() 66 * 67 * @since 1.4 68 */ 69 public class BufferCapabilities implements Cloneable 70 { 71 /** 72 * A type-safe enumeration of buffer flipping results. 73 * 74 * @see AttributeValue 75 */ 76 public static final class FlipContents extends AttributeValue 77 { 78 /** 79 * The names of the different flipping results. 80 */ 81 private static final String[] NAMES 82 = { "undefined", "background", "prior", "copied" }; 83 84 /** 85 * The contents of the back buffer are undefined after flipping. 86 */ 87 public static final FlipContents UNDEFINED = new FlipContents(0); 88 89 /** 90 * The back buffer is cleared with the background color after 91 * flipping. 92 */ 93 public static final FlipContents BACKGROUND = new FlipContents(1); 94 95 /** 96 * The back buffer contains the pre-flipping contents of the front 97 * buffer after flipping. In other words a true "flip" has been 98 * performed. 99 */ 100 public static final FlipContents PRIOR = new FlipContents(2); 101 102 /** 103 * The back buffer has the same contents as the front buffer after 104 * flipping. 105 */ 106 public static final FlipContents COPIED = new FlipContents(3); 107 108 /** 109 * Create a new flipping result descriptor. 110 * 111 * @param value the enumeration value 112 */ FlipContents(int value)113 private FlipContents(int value) 114 { 115 super(value, NAMES); 116 } 117 } 118 119 /** 120 * Front buffer capabilities descriptor. 121 */ 122 private final ImageCapabilities front; 123 124 /** 125 * Back buffer capabilities descriptor. 126 */ 127 private final ImageCapabilities back; 128 129 /** 130 * Describes the results of a "flip" operation. 131 */ 132 private final FlipContents flip; 133 134 /** 135 * Creates a buffer capabilities object. 136 * 137 * @param frontCaps front buffer capabilities descriptor 138 * @param backCaps back buffer capabilities descriptor 139 * @param flip the results of a flip operation or null if 140 * flipping is not supported 141 * 142 * @exception IllegalArgumentException if frontCaps or backCaps is 143 * null 144 */ BufferCapabilities(ImageCapabilities frontCaps, ImageCapabilities backCaps, FlipContents flip)145 public BufferCapabilities(ImageCapabilities frontCaps, 146 ImageCapabilities backCaps, 147 FlipContents flip) 148 { 149 if (frontCaps == null || backCaps == null) 150 throw new IllegalArgumentException(); 151 this.front = frontCaps; 152 this.back = backCaps; 153 this.flip = flip; 154 } 155 156 /** 157 * Retrieve the front buffer's image capabilities. 158 * 159 * @return the front buffer's image capabilities 160 */ getFrontBufferCapabilities()161 public ImageCapabilities getFrontBufferCapabilities() 162 { 163 return front; 164 } 165 166 /** 167 * Retrieve the back buffer's image capabilities. 168 * 169 * @return the back buffer's image capabilities 170 */ getBackBufferCapabilities()171 public ImageCapabilities getBackBufferCapabilities() 172 { 173 return back; 174 } 175 176 /** 177 * Return whether or not flipping is supported. 178 * 179 * @return true if flipping is supported, false otherwise 180 */ isPageFlipping()181 public boolean isPageFlipping() 182 { 183 return flip != null; 184 } 185 186 /** 187 * Retrieve the result of a flipping operation. If this method 188 * returns null then flipping is not supported. This implies that 189 * "blitting", a fast block transfer, is used to copy the contents 190 * of the back buffer to the front buffer. Other possible return 191 * values are: 192 * <ul> 193 * <li><code>FlipContents.UNDEFINED</code> the contents of the 194 * back buffer are undefined after flipping.</li> 195 * <li><code>FlipContents.BACKGROUND</code> the contents of the 196 * back buffer are cleared to the background color after 197 * flipping.</li> 198 * <li><code>FlipContents.PRIOR</code> the back buffer contains 199 * the pre-flipping contents of the front * buffer after 200 * flipping.</li> 201 * <li><code>FlipContents.COPIED</code> the back buffer has the 202 * same contents as the front buffer after flipping.</li> 203 * </ul> 204 * 205 * @return the result of a flipping operation or null if flipping is 206 * not supported 207 */ getFlipContents()208 public FlipContents getFlipContents() 209 { 210 return flip; 211 } 212 213 /** 214 * Returns true if flipping is only supported in fullscreen mode. 215 * 216 * @return true if flipping is only supported in fullscreen mode, 217 * false otherwise 218 */ isFullScreenRequired()219 public boolean isFullScreenRequired() 220 { 221 return true; 222 } 223 224 /** 225 * Returns true if flipping can involve more than two buffers. One 226 * or more intermediate buffers may be available in addition to the 227 * front and back buffers. 228 * 229 * @return true if there are more than two buffers available for 230 * flipping, false otherwise 231 */ isMultiBufferAvailable()232 public boolean isMultiBufferAvailable() 233 { 234 return false; 235 } 236 237 /** 238 * Clone this buffering capability descriptor. 239 * 240 * @return a clone of this buffer capability descriptor 241 */ clone()242 public Object clone() 243 { 244 try 245 { 246 return super.clone(); 247 } 248 catch (CloneNotSupportedException e) 249 { 250 throw (Error) new InternalError().initCause(e); 251 } 252 } 253 } 254