/* * Copyright (c) 1995, 2010, 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</code> 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</code> class in * order to get useful functionality such as creating a custom * component. The <code>paint</code> method must be overridden * in order to perform custom graphics on the canvas. * * @author Sami Shaio * @since JDK1.0 */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. * * @param config a reference to a GraphicsConfiguration object. * * @see GraphicsConfiguration */ public Canvas(GraphicsConfiguration config) { this(); setGraphicsConfiguration(config); } @Override void setGraphicsConfiguration(GraphicsConfiguration gc) { synchronized(getTreeLock()) { CanvasPeer peer = (CanvasPeer)getPeer(); 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.Toolkit#createCanvas(java.awt.Canvas) * @see java.awt.Component#getToolkit() */ public void addNotify() { synchronized (getTreeLock()) { if (peer == null) peer = getToolkit().createCanvas(this); super.addNotify(); } } /** * Paints this canvas. * <p> * Most applications that subclass <code>Canvas</code> 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</code>. * The canvas is first cleared by filling it with the background * color, and then completely redrawn by calling this canvas's * <code>paint</code> 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</code> * 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</code> * @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</code> * @see #getBufferStrategy * @since 1.4 */ public void createBufferStrategy(int numBuffers, BufferCapabilities caps) throws AWTException { super.createBufferStrategy(numBuffers, caps); } /** * Returns the <code>BufferStrategy</code> used by this component. This * method will return null if a <code>BufferStrategy</code> 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</code> 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}
/*
* Copyright (c) 1995, 2010, 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</code> 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</code> class in
* order to get useful functionality such as creating a custom
* component. The <code>paint</code> method must be overridden
* in order to perform custom graphics on the canvas.
*
* @author Sami Shaio
* @since JDK1.0
*/
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.
*
* @param config a reference to a GraphicsConfiguration object.
*
* @see GraphicsConfiguration
*/
public Canvas(GraphicsConfiguration config) {
this();
setGraphicsConfiguration(config);
}
@Override
void setGraphicsConfiguration(GraphicsConfiguration gc) {
synchronized(getTreeLock()) {
CanvasPeer peer = (CanvasPeer)getPeer();
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.Toolkit#createCanvas(java.awt.Canvas)
* @see java.awt.Component#getToolkit()
*/
public void addNotify() {
synchronized (getTreeLock()) {
if (peer == null)
peer = getToolkit().createCanvas(this);
super.addNotify();
}
}
/**
* Paints this canvas.
* <p>
* Most applications that subclass <code>Canvas</code> 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</code>.
* The canvas is first cleared by filling it with the background
* color, and then completely redrawn by calling this canvas's
* <code>paint</code> 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</code>
* 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</code>
* @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</code>
* @see #getBufferStrategy
* @since 1.4
*/
public void createBufferStrategy(int numBuffers,
BufferCapabilities caps) throws AWTException {
super.createBufferStrategy(numBuffers, caps);
}
/**
* Returns the <code>BufferStrategy</code> used by this component. This
* method will return null if a <code>BufferStrategy</code> 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</code> 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
}