0N/A/*
3261N/A * Copyright (c) 1995, 2010, Oracle and/or its affiliates. All rights reserved.
0N/A * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
0N/A *
0N/A * This code is free software; you can redistribute it and/or modify it
0N/A * under the terms of the GNU General Public License version 2 only, as
2362N/A * published by the Free Software Foundation. Oracle designates this
0N/A * particular file as subject to the "Classpath" exception as provided
2362N/A * by Oracle in the LICENSE file that accompanied this code.
0N/A *
0N/A * This code is distributed in the hope that it will be useful, but WITHOUT
0N/A * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
0N/A * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
0N/A * version 2 for more details (a copy is included in the LICENSE file that
0N/A * accompanied this code).
0N/A *
0N/A * You should have received a copy of the GNU General Public License version
0N/A * 2 along with this work; if not, write to the Free Software Foundation,
0N/A * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
0N/A *
2362N/A * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
2362N/A * or visit www.oracle.com if you need additional information or have any
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0N/A */
0N/Apackage java.awt;
0N/A
0N/Aimport java.awt.image.BufferStrategy;
1053N/Aimport java.awt.peer.CanvasPeer;
0N/Aimport javax.accessibility.*;
0N/A
0N/A/**
0N/A * A <code>Canvas</code> component represents a blank rectangular
0N/A * area of the screen onto which the application can draw or from
0N/A * which the application can trap input events from the user.
0N/A * <p>
0N/A * An application must subclass the <code>Canvas</code> class in
0N/A * order to get useful functionality such as creating a custom
0N/A * component. The <code>paint</code> method must be overridden
0N/A * in order to perform custom graphics on the canvas.
0N/A *
0N/A * @author Sami Shaio
0N/A * @since JDK1.0
0N/A */
0N/Apublic class Canvas extends Component implements Accessible {
0N/A
0N/A private static final String base = "canvas";
0N/A private static int nameCounter = 0;
0N/A
0N/A /*
0N/A * JDK 1.1 serialVersionUID
0N/A */
0N/A private static final long serialVersionUID = -2284879212465893870L;
0N/A
0N/A /**
0N/A * Constructs a new Canvas.
0N/A */
0N/A public Canvas() {
0N/A }
0N/A
0N/A /**
0N/A * Constructs a new Canvas given a GraphicsConfiguration object.
0N/A *
0N/A * @param config a reference to a GraphicsConfiguration object.
0N/A *
0N/A * @see GraphicsConfiguration
0N/A */
0N/A public Canvas(GraphicsConfiguration config) {
0N/A this();
1053N/A setGraphicsConfiguration(config);
1053N/A }
1053N/A
1053N/A @Override
1053N/A void setGraphicsConfiguration(GraphicsConfiguration gc) {
2862N/A synchronized(getTreeLock()) {
2862N/A CanvasPeer peer = (CanvasPeer)getPeer();
2862N/A if (peer != null) {
2862N/A gc = peer.getAppropriateGraphicsConfiguration(gc);
2862N/A }
2862N/A super.setGraphicsConfiguration(gc);
1053N/A }
0N/A }
0N/A
0N/A /**
0N/A * Construct a name for this component. Called by getName() when the
0N/A * name is null.
0N/A */
0N/A String constructComponentName() {
0N/A synchronized (Canvas.class) {
0N/A return base + nameCounter++;
0N/A }
0N/A }
0N/A
0N/A /**
0N/A * Creates the peer of the canvas. This peer allows you to change the
0N/A * user interface of the canvas without changing its functionality.
0N/A * @see java.awt.Toolkit#createCanvas(java.awt.Canvas)
0N/A * @see java.awt.Component#getToolkit()
0N/A */
0N/A public void addNotify() {
0N/A synchronized (getTreeLock()) {
0N/A if (peer == null)
0N/A peer = getToolkit().createCanvas(this);
0N/A super.addNotify();
0N/A }
0N/A }
0N/A
0N/A /**
0N/A * Paints this canvas.
0N/A * <p>
0N/A * Most applications that subclass <code>Canvas</code> should
0N/A * override this method in order to perform some useful operation
0N/A * (typically, custom painting of the canvas).
0N/A * The default operation is simply to clear the canvas.
0N/A * Applications that override this method need not call
0N/A * super.paint(g).
0N/A *
0N/A * @param g the specified Graphics context
0N/A * @see #update(Graphics)
0N/A * @see Component#paint(Graphics)
0N/A */
0N/A public void paint(Graphics g) {
0N/A g.clearRect(0, 0, width, height);
0N/A }
0N/A
0N/A /**
0N/A * Updates this canvas.
0N/A * <p>
0N/A * This method is called in response to a call to <code>repaint</code>.
0N/A * The canvas is first cleared by filling it with the background
0N/A * color, and then completely redrawn by calling this canvas's
0N/A * <code>paint</code> method.
0N/A * Note: applications that override this method should either call
0N/A * super.update(g) or incorporate the functionality described
0N/A * above into their own code.
0N/A *
0N/A * @param g the specified Graphics context
0N/A * @see #paint(Graphics)
0N/A * @see Component#update(Graphics)
0N/A */
0N/A public void update(Graphics g) {
0N/A g.clearRect(0, 0, width, height);
0N/A paint(g);
0N/A }
0N/A
0N/A boolean postsOldMouseEvents() {
0N/A return true;
0N/A }
0N/A
0N/A /**
0N/A * Creates a new strategy for multi-buffering on this component.
0N/A * Multi-buffering is useful for rendering performance. This method
0N/A * attempts to create the best strategy available with the number of
0N/A * buffers supplied. It will always create a <code>BufferStrategy</code>
0N/A * with that number of buffers.
0N/A * A page-flipping strategy is attempted first, then a blitting strategy
0N/A * using accelerated buffers. Finally, an unaccelerated blitting
0N/A * strategy is used.
0N/A * <p>
0N/A * Each time this method is called,
0N/A * the existing buffer strategy for this component is discarded.
0N/A * @param numBuffers number of buffers to create, including the front buffer
0N/A * @exception IllegalArgumentException if numBuffers is less than 1.
0N/A * @exception IllegalStateException if the component is not displayable
0N/A * @see #isDisplayable
0N/A * @see #getBufferStrategy
0N/A * @since 1.4
0N/A */
0N/A public void createBufferStrategy(int numBuffers) {
0N/A super.createBufferStrategy(numBuffers);
0N/A }
0N/A
0N/A /**
0N/A * Creates a new strategy for multi-buffering on this component with the
0N/A * required buffer capabilities. This is useful, for example, if only
0N/A * accelerated memory or page flipping is desired (as specified by the
0N/A * buffer capabilities).
0N/A * <p>
0N/A * Each time this method
0N/A * is called, the existing buffer strategy for this component is discarded.
0N/A * @param numBuffers number of buffers to create
0N/A * @param caps the required capabilities for creating the buffer strategy;
0N/A * cannot be <code>null</code>
0N/A * @exception AWTException if the capabilities supplied could not be
0N/A * supported or met; this may happen, for example, if there is not enough
0N/A * accelerated memory currently available, or if page flipping is specified
0N/A * but not possible.
0N/A * @exception IllegalArgumentException if numBuffers is less than 1, or if
0N/A * caps is <code>null</code>
0N/A * @see #getBufferStrategy
0N/A * @since 1.4
0N/A */
0N/A public void createBufferStrategy(int numBuffers,
0N/A BufferCapabilities caps) throws AWTException {
0N/A super.createBufferStrategy(numBuffers, caps);
0N/A }
0N/A
0N/A /**
0N/A * Returns the <code>BufferStrategy</code> used by this component. This
0N/A * method will return null if a <code>BufferStrategy</code> has not yet
0N/A * been created or has been disposed.
0N/A *
0N/A * @return the buffer strategy used by this component
0N/A * @see #createBufferStrategy
0N/A * @since 1.4
0N/A */
0N/A public BufferStrategy getBufferStrategy() {
0N/A return super.getBufferStrategy();
0N/A }
0N/A
0N/A /*
0N/A * --- Accessibility Support ---
0N/A *
0N/A */
0N/A
0N/A /**
0N/A * Gets the AccessibleContext associated with this Canvas.
0N/A * For canvases, the AccessibleContext takes the form of an
0N/A * AccessibleAWTCanvas.
0N/A * A new AccessibleAWTCanvas instance is created if necessary.
0N/A *
0N/A * @return an AccessibleAWTCanvas that serves as the
0N/A * AccessibleContext of this Canvas
0N/A * @since 1.3
0N/A */
0N/A public AccessibleContext getAccessibleContext() {
0N/A if (accessibleContext == null) {
0N/A accessibleContext = new AccessibleAWTCanvas();
0N/A }
0N/A return accessibleContext;
0N/A }
0N/A
0N/A /**
0N/A * This class implements accessibility support for the
0N/A * <code>Canvas</code> class. It provides an implementation of the
0N/A * Java Accessibility API appropriate to canvas user-interface elements.
0N/A * @since 1.3
0N/A */
0N/A protected class AccessibleAWTCanvas extends AccessibleAWTComponent
0N/A {
0N/A private static final long serialVersionUID = -6325592262103146699L;
0N/A
0N/A /**
0N/A * Get the role of this object.
0N/A *
0N/A * @return an instance of AccessibleRole describing the role of the
0N/A * object
0N/A * @see AccessibleRole
0N/A */
0N/A public AccessibleRole getAccessibleRole() {
0N/A return AccessibleRole.CANVAS;
0N/A }
0N/A
0N/A } // inner class AccessibleAWTCanvas
0N/A}