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| 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 | } | ||