Showing the changes to java/pkg/java/awt/Canvas.java (1 of 18352 files). Show all
Unified · Split
| @@ -0,0 +1,254 @@ | ||
| 1 | +/* | |
| 2 | + * Copyright (c) 1995, 2010, 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 java.awt; | |
| 26 | + | |
| 27 | +import java.awt.image.BufferStrategy; | |
| 28 | +import java.awt.peer.CanvasPeer; | |
| 29 | +import javax.accessibility.*; | |
| 30 | + | |
| 31 | +/** | |
| 32 | + * A <code>Canvas</code> component represents a blank rectangular | |
| 33 | + * area of the screen onto which the application can draw or from | |
| 34 | + * which the application can trap input events from the user. | |
| 35 | + * <p> | |
| 36 | + * An application must subclass the <code>Canvas</code> class in | |
| 37 | + * order to get useful functionality such as creating a custom | |
| 38 | + * component. The <code>paint</code> method must be overridden | |
| 39 | + * in order to perform custom graphics on the canvas. | |
| 40 | + * | |
| 41 | + * @author Sami Shaio | |
| 42 | + * @since JDK1.0 | |
| 43 | + */ | |
| 44 | +public class Canvas extends Component implements Accessible { | |
| 45 | + | |
| 46 | + private static final String base = "canvas"; | |
| 47 | + private static int nameCounter = 0; | |
| 48 | + | |
| 49 | + /* | |
| 50 | + * JDK 1.1 serialVersionUID | |
| 51 | + */ | |
| 52 | + private static final long serialVersionUID = -2284879212465893870L; | |
| 53 | + | |
| 54 | + /** | |
| 55 | + * Constructs a new Canvas. | |
| 56 | + */ | |
| 57 | + public Canvas() { | |
| 58 | + } | |
| 59 | + | |
| 60 | + /** | |
| 61 | + * Constructs a new Canvas given a GraphicsConfiguration object. | |
| 62 | + * | |
| 63 | + * @param config a reference to a GraphicsConfiguration object. | |
| 64 | + * | |
| 65 | + * @see GraphicsConfiguration | |
| 66 | + */ | |
| 67 | + public Canvas(GraphicsConfiguration config) { | |
| 68 | + this(); | |
| 69 | + setGraphicsConfiguration(config); | |
| 70 | + } | |
| 71 | + | |
| 72 | + @Override | |
| 73 | + void setGraphicsConfiguration(GraphicsConfiguration gc) { | |
| 74 | + synchronized(getTreeLock()) { | |
| 75 | + CanvasPeer peer = (CanvasPeer)getPeer(); | |
| 76 | + if (peer != null) { | |
| 77 | + gc = peer.getAppropriateGraphicsConfiguration(gc); | |
| 78 | + } | |
| 79 | + super.setGraphicsConfiguration(gc); | |
| 80 | + } | |
| 81 | + } | |
| 82 | + | |
| 83 | + /** | |
| 84 | + * Construct a name for this component. Called by getName() when the | |
| 85 | + * name is null. | |
| 86 | + */ | |
| 87 | + String constructComponentName() { | |
| 88 | + synchronized (Canvas.class) { | |
| 89 | + return base + nameCounter++; | |
| 90 | + } | |
| 91 | + } | |
| 92 | + | |
| 93 | + /** | |
| 94 | + * Creates the peer of the canvas. This peer allows you to change the | |
| 95 | + * user interface of the canvas without changing its functionality. | |
| 96 | + * @see java.awt.Toolkit#createCanvas(java.awt.Canvas) | |
| 97 | + * @see java.awt.Component#getToolkit() | |
| 98 | + */ | |
| 99 | + public void addNotify() { | |
| 100 | + synchronized (getTreeLock()) { | |
| 101 | + if (peer == null) | |
| 102 | + peer = getToolkit().createCanvas(this); | |
| 103 | + super.addNotify(); | |
| 104 | + } | |
| 105 | + } | |
| 106 | + | |
| 107 | + /** | |
| 108 | + * Paints this canvas. | |
| 109 | + * <p> | |
| 110 | + * Most applications that subclass <code>Canvas</code> should | |
| 111 | + * override this method in order to perform some useful operation | |
| 112 | + * (typically, custom painting of the canvas). | |
| 113 | + * The default operation is simply to clear the canvas. | |
| 114 | + * Applications that override this method need not call | |
| 115 | + * super.paint(g). | |
| 116 | + * | |
| 117 | + * @param g the specified Graphics context | |
| 118 | + * @see #update(Graphics) | |
| 119 | + * @see Component#paint(Graphics) | |
| 120 | + */ | |
| 121 | + public void paint(Graphics g) { | |
| 122 | + g.clearRect(0, 0, width, height); | |
| 123 | + } | |
| 124 | + | |
| 125 | + /** | |
| 126 | + * Updates this canvas. | |
| 127 | + * <p> | |
| 128 | + * This method is called in response to a call to <code>repaint</code>. | |
| 129 | + * The canvas is first cleared by filling it with the background | |
| 130 | + * color, and then completely redrawn by calling this canvas's | |
| 131 | + * <code>paint</code> method. | |
| 132 | + * Note: applications that override this method should either call | |
| 133 | + * super.update(g) or incorporate the functionality described | |
| 134 | + * above into their own code. | |
| 135 | + * | |
| 136 | + * @param g the specified Graphics context | |
| 137 | + * @see #paint(Graphics) | |
| 138 | + * @see Component#update(Graphics) | |
| 139 | + */ | |
| 140 | + public void update(Graphics g) { | |
| 141 | + g.clearRect(0, 0, width, height); | |
| 142 | + paint(g); | |
| 143 | + } | |
| 144 | + | |
| 145 | + boolean postsOldMouseEvents() { | |
| 146 | + return true; | |
| 147 | + } | |
| 148 | + | |
| 149 | + /** | |
| 150 | + * Creates a new strategy for multi-buffering on this component. | |
| 151 | + * Multi-buffering is useful for rendering performance. This method | |
| 152 | + * attempts to create the best strategy available with the number of | |
| 153 | + * buffers supplied. It will always create a <code>BufferStrategy</code> | |
| 154 | + * with that number of buffers. | |
| 155 | + * A page-flipping strategy is attempted first, then a blitting strategy | |
| 156 | + * using accelerated buffers. Finally, an unaccelerated blitting | |
| 157 | + * strategy is used. | |
| 158 | + * <p> | |
| 159 | + * Each time this method is called, | |
| 160 | + * the existing buffer strategy for this component is discarded. | |
| 161 | + * @param numBuffers number of buffers to create, including the front buffer | |
| 162 | + * @exception IllegalArgumentException if numBuffers is less than 1. | |
| 163 | + * @exception IllegalStateException if the component is not displayable | |
| 164 | + * @see #isDisplayable | |
| 165 | + * @see #getBufferStrategy | |
| 166 | + * @since 1.4 | |
| 167 | + */ | |
| 168 | + public void createBufferStrategy(int numBuffers) { | |
| 169 | + super.createBufferStrategy(numBuffers); | |
| 170 | + } | |
| 171 | + | |
| 172 | + /** | |
| 173 | + * Creates a new strategy for multi-buffering on this component with the | |
| 174 | + * required buffer capabilities. This is useful, for example, if only | |
| 175 | + * accelerated memory or page flipping is desired (as specified by the | |
| 176 | + * buffer capabilities). | |
| 177 | + * <p> | |
| 178 | + * Each time this method | |
| 179 | + * is called, the existing buffer strategy for this component is discarded. | |
| 180 | + * @param numBuffers number of buffers to create | |
| 181 | + * @param caps the required capabilities for creating the buffer strategy; | |
| 182 | + * cannot be <code>null</code> | |
| 183 | + * @exception AWTException if the capabilities supplied could not be | |
| 184 | + * supported or met; this may happen, for example, if there is not enough | |
| 185 | + * accelerated memory currently available, or if page flipping is specified | |
| 186 | + * but not possible. | |
| 187 | + * @exception IllegalArgumentException if numBuffers is less than 1, or if | |
| 188 | + * caps is <code>null</code> | |
| 189 | + * @see #getBufferStrategy | |
| 190 | + * @since 1.4 | |
| 191 | + */ | |
| 192 | + public void createBufferStrategy(int numBuffers, | |
| 193 | + BufferCapabilities caps) throws AWTException { | |
| 194 | + super.createBufferStrategy(numBuffers, caps); | |
| 195 | + } | |
| 196 | + | |
| 197 | + /** | |
| 198 | + * Returns the <code>BufferStrategy</code> used by this component. This | |
| 199 | + * method will return null if a <code>BufferStrategy</code> has not yet | |
| 200 | + * been created or has been disposed. | |
| 201 | + * | |
| 202 | + * @return the buffer strategy used by this component | |
| 203 | + * @see #createBufferStrategy | |
| 204 | + * @since 1.4 | |
| 205 | + */ | |
| 206 | + public BufferStrategy getBufferStrategy() { | |
| 207 | + return super.getBufferStrategy(); | |
| 208 | + } | |
| 209 | + | |
| 210 | + /* | |
| 211 | + * --- Accessibility Support --- | |
| 212 | + * | |
| 213 | + */ | |
| 214 | + | |
| 215 | + /** | |
| 216 | + * Gets the AccessibleContext associated with this Canvas. | |
| 217 | + * For canvases, the AccessibleContext takes the form of an | |
| 218 | + * AccessibleAWTCanvas. | |
| 219 | + * A new AccessibleAWTCanvas instance is created if necessary. | |
| 220 | + * | |
| 221 | + * @return an AccessibleAWTCanvas that serves as the | |
| 222 | + * AccessibleContext of this Canvas | |
| 223 | + * @since 1.3 | |
| 224 | + */ | |
| 225 | + public AccessibleContext getAccessibleContext() { | |
| 226 | + if (accessibleContext == null) { | |
| 227 | + accessibleContext = new AccessibleAWTCanvas(); | |
| 228 | + } | |
| 229 | + return accessibleContext; | |
| 230 | + } | |
| 231 | + | |
| 232 | + /** | |
| 233 | + * This class implements accessibility support for the | |
| 234 | + * <code>Canvas</code> class. It provides an implementation of the | |
| 235 | + * Java Accessibility API appropriate to canvas user-interface elements. | |
| 236 | + * @since 1.3 | |
| 237 | + */ | |
| 238 | + protected class AccessibleAWTCanvas extends AccessibleAWTComponent | |
| 239 | + { | |
| 240 | + private static final long serialVersionUID = -6325592262103146699L; | |
| 241 | + | |
| 242 | + /** | |
| 243 | + * Get the role of this object. | |
| 244 | + * | |
| 245 | + * @return an instance of AccessibleRole describing the role of the | |
| 246 | + * object | |
| 247 | + * @see AccessibleRole | |
| 248 | + */ | |
| 249 | + public AccessibleRole getAccessibleRole() { | |
| 250 | + return AccessibleRole.CANVAS; | |
| 251 | + } | |
| 252 | + | |
| 253 | + } // inner class AccessibleAWTCanvas | |
| 254 | +} | |