| /* |
| * Copyright (c) 1995, 2015, 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; |
| |
| import java.awt.image.BufferStrategy; |
| import java.awt.peer.CanvasPeer; |
| import javax.accessibility.*; |
| |
| /** |
| * A {@code Canvas} component represents a blank rectangular |
| * area of the screen onto which the application can draw or from |
| * which the application can trap input events from the user. |
| * <p> |
| * An application must subclass the {@code Canvas} class in |
| * order to get useful functionality such as creating a custom |
| * component. The {@code paint} method must be overridden |
| * in order to perform custom graphics on the canvas. |
| * |
| * @author Sami Shaio |
| * @since 1.0 |
| */ |
| public class Canvas extends Component implements Accessible { |
| |
| private static final String base = "canvas"; |
| private static int nameCounter = 0; |
| |
| /* |
| * JDK 1.1 serialVersionUID |
| */ |
| private static final long serialVersionUID = -2284879212465893870L; |
| |
| /** |
| * Constructs a new Canvas. |
| */ |
| public Canvas() { |
| } |
| |
| /** |
| * Constructs a new Canvas given a GraphicsConfiguration object. If null is |
| * passed, then the default GraphicsConfiguration will be used. |
| * |
| * @param config a reference to a GraphicsConfiguration object or null |
| * |
| * @see GraphicsConfiguration |
| * @see Component#getGraphicsConfiguration() |
| */ |
| public Canvas(GraphicsConfiguration config) { |
| this(); |
| setGraphicsConfiguration(config); |
| } |
| |
| @Override |
| void setGraphicsConfiguration(GraphicsConfiguration gc) { |
| synchronized(getTreeLock()) { |
| CanvasPeer peer = (CanvasPeer) this.peer; |
| if (peer != null) { |
| gc = peer.getAppropriateGraphicsConfiguration(gc); |
| } |
| super.setGraphicsConfiguration(gc); |
| } |
| } |
| |
| /** |
| * Construct a name for this component. Called by getName() when the |
| * name is null. |
| */ |
| String constructComponentName() { |
| synchronized (Canvas.class) { |
| return base + nameCounter++; |
| } |
| } |
| |
| /** |
| * Creates the peer of the canvas. This peer allows you to change the |
| * user interface of the canvas without changing its functionality. |
| * @see java.awt.Component#getToolkit() |
| */ |
| public void addNotify() { |
| synchronized (getTreeLock()) { |
| if (peer == null) |
| peer = getComponentFactory().createCanvas(this); |
| super.addNotify(); |
| } |
| } |
| |
| /** |
| * Paints this canvas. |
| * <p> |
| * Most applications that subclass {@code Canvas} should |
| * override this method in order to perform some useful operation |
| * (typically, custom painting of the canvas). |
| * The default operation is simply to clear the canvas. |
| * Applications that override this method need not call |
| * super.paint(g). |
| * |
| * @param g the specified Graphics context |
| * @see #update(Graphics) |
| * @see Component#paint(Graphics) |
| */ |
| public void paint(Graphics g) { |
| g.clearRect(0, 0, width, height); |
| } |
| |
| /** |
| * Updates this canvas. |
| * <p> |
| * This method is called in response to a call to {@code repaint}. |
| * The canvas is first cleared by filling it with the background |
| * color, and then completely redrawn by calling this canvas's |
| * {@code paint} method. |
| * Note: applications that override this method should either call |
| * super.update(g) or incorporate the functionality described |
| * above into their own code. |
| * |
| * @param g the specified Graphics context |
| * @see #paint(Graphics) |
| * @see Component#update(Graphics) |
| */ |
| public void update(Graphics g) { |
| g.clearRect(0, 0, width, height); |
| paint(g); |
| } |
| |
| boolean postsOldMouseEvents() { |
| return true; |
| } |
| |
| /** |
| * Creates a new strategy for multi-buffering on this component. |
| * Multi-buffering is useful for rendering performance. This method |
| * attempts to create the best strategy available with the number of |
| * buffers supplied. It will always create a {@code BufferStrategy} |
| * with that number of buffers. |
| * A page-flipping strategy is attempted first, then a blitting strategy |
| * using accelerated buffers. Finally, an unaccelerated blitting |
| * strategy is used. |
| * <p> |
| * Each time this method is called, |
| * the existing buffer strategy for this component is discarded. |
| * @param numBuffers number of buffers to create, including the front buffer |
| * @exception IllegalArgumentException if numBuffers is less than 1. |
| * @exception IllegalStateException if the component is not displayable |
| * @see #isDisplayable |
| * @see #getBufferStrategy |
| * @since 1.4 |
| */ |
| public void createBufferStrategy(int numBuffers) { |
| super.createBufferStrategy(numBuffers); |
| } |
| |
| /** |
| * Creates a new strategy for multi-buffering on this component with the |
| * required buffer capabilities. This is useful, for example, if only |
| * accelerated memory or page flipping is desired (as specified by the |
| * buffer capabilities). |
| * <p> |
| * Each time this method |
| * is called, the existing buffer strategy for this component is discarded. |
| * @param numBuffers number of buffers to create |
| * @param caps the required capabilities for creating the buffer strategy; |
| * cannot be {@code null} |
| * @exception AWTException if the capabilities supplied could not be |
| * supported or met; this may happen, for example, if there is not enough |
| * accelerated memory currently available, or if page flipping is specified |
| * but not possible. |
| * @exception IllegalArgumentException if numBuffers is less than 1, or if |
| * caps is {@code null} |
| * @see #getBufferStrategy |
| * @since 1.4 |
| */ |
| public void createBufferStrategy(int numBuffers, |
| BufferCapabilities caps) throws AWTException { |
| super.createBufferStrategy(numBuffers, caps); |
| } |
| |
| /** |
| * Returns the {@code BufferStrategy} used by this component. This |
| * method will return null if a {@code BufferStrategy} has not yet |
| * been created or has been disposed. |
| * |
| * @return the buffer strategy used by this component |
| * @see #createBufferStrategy |
| * @since 1.4 |
| */ |
| public BufferStrategy getBufferStrategy() { |
| return super.getBufferStrategy(); |
| } |
| |
| /* |
| * --- Accessibility Support --- |
| * |
| */ |
| |
| /** |
| * Gets the AccessibleContext associated with this Canvas. |
| * For canvases, the AccessibleContext takes the form of an |
| * AccessibleAWTCanvas. |
| * A new AccessibleAWTCanvas instance is created if necessary. |
| * |
| * @return an AccessibleAWTCanvas that serves as the |
| * AccessibleContext of this Canvas |
| * @since 1.3 |
| */ |
| public AccessibleContext getAccessibleContext() { |
| if (accessibleContext == null) { |
| accessibleContext = new AccessibleAWTCanvas(); |
| } |
| return accessibleContext; |
| } |
| |
| /** |
| * This class implements accessibility support for the |
| * {@code Canvas} class. It provides an implementation of the |
| * Java Accessibility API appropriate to canvas user-interface elements. |
| * @since 1.3 |
| */ |
| protected class AccessibleAWTCanvas extends AccessibleAWTComponent |
| { |
| private static final long serialVersionUID = -6325592262103146699L; |
| |
| /** |
| * Get the role of this object. |
| * |
| * @return an instance of AccessibleRole describing the role of the |
| * object |
| * @see AccessibleRole |
| */ |
| public AccessibleRole getAccessibleRole() { |
| return AccessibleRole.CANVAS; |
| } |
| |
| } // inner class AccessibleAWTCanvas |
| } |