Canvas.java revision 0
2115N/A/*
2362N/A * Copyright 1995-2007 Sun Microsystems, Inc. All Rights Reserved.
2115N/A * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
2115N/A *
2115N/A * This code is free software; you can redistribute it and/or modify it
2115N/A * under the terms of the GNU General Public License version 2 only, as
2115N/A * published by the Free Software Foundation. Sun designates this
2115N/A * particular file as subject to the "Classpath" exception as provided
2115N/A * by Sun in the LICENSE file that accompanied this code.
2115N/A *
2115N/A * This code is distributed in the hope that it will be useful, but WITHOUT
2115N/A * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
2115N/A * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
2115N/A * version 2 for more details (a copy is included in the LICENSE file that
2115N/A * accompanied this code).
2115N/A *
2115N/A * You should have received a copy of the GNU General Public License version
2115N/A * 2 along with this work; if not, write to the Free Software Foundation,
2362N/A * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
2362N/A *
2362N/A * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
2115N/A * CA 95054 USA or visit www.sun.com if you need additional information or
2115N/A * have any questions.
2115N/A */
2115N/Apackage java.awt;
2115N/A
2115N/Aimport java.awt.image.BufferStrategy;
2115N/Aimport javax.accessibility.*;
2115N/A
2115N/A/**
2115N/A * A <code>Canvas</code> component represents a blank rectangular
2115N/A * area of the screen onto which the application can draw or from
2115N/A * which the application can trap input events from the user.
2115N/A * <p>
2115N/A * An application must subclass the <code>Canvas</code> class in
2115N/A * order to get useful functionality such as creating a custom
2115N/A * component. The <code>paint</code> method must be overridden
2115N/A * in order to perform custom graphics on the canvas.
2115N/A *
2115N/A * @author Sami Shaio
2115N/A * @since JDK1.0
2115N/A */
2115N/Apublic class Canvas extends Component implements Accessible {
2115N/A
2115N/A private static final String base = "canvas";
2115N/A private static int nameCounter = 0;
2115N/A
2115N/A /*
2115N/A * JDK 1.1 serialVersionUID
2115N/A */
2115N/A private static final long serialVersionUID = -2284879212465893870L;
2115N/A
2115N/A /**
2115N/A * Constructs a new Canvas.
2115N/A */
2115N/A public Canvas() {
2115N/A }
2115N/A
2115N/A /**
2115N/A * Constructs a new Canvas given a GraphicsConfiguration object.
2115N/A *
2115N/A * @param config a reference to a GraphicsConfiguration object.
2115N/A *
2115N/A * @see GraphicsConfiguration
2115N/A */
2115N/A public Canvas(GraphicsConfiguration config) {
2115N/A this();
2115N/A graphicsConfig = config;
2115N/A }
2115N/A
2115N/A /**
2115N/A * Construct a name for this component. Called by getName() when the
2115N/A * name is null.
2115N/A */
2115N/A String constructComponentName() {
2115N/A synchronized (Canvas.class) {
2115N/A return base + nameCounter++;
2115N/A }
2115N/A }
2115N/A
2115N/A /**
2115N/A * Creates the peer of the canvas. This peer allows you to change the
2115N/A * user interface of the canvas without changing its functionality.
2115N/A * @see java.awt.Toolkit#createCanvas(java.awt.Canvas)
2115N/A * @see java.awt.Component#getToolkit()
2115N/A */
2115N/A public void addNotify() {
2115N/A synchronized (getTreeLock()) {
2115N/A if (peer == null)
2115N/A peer = getToolkit().createCanvas(this);
2115N/A super.addNotify();
2115N/A }
2115N/A }
2115N/A
2115N/A /**
2115N/A * Paints this canvas.
2115N/A * <p>
2115N/A * Most applications that subclass <code>Canvas</code> should
2115N/A * override this method in order to perform some useful operation
2115N/A * (typically, custom painting of the canvas).
2115N/A * The default operation is simply to clear the canvas.
2115N/A * Applications that override this method need not call
2115N/A * super.paint(g).
2115N/A *
2115N/A * @param g the specified Graphics context
2115N/A * @see #update(Graphics)
2115N/A * @see Component#paint(Graphics)
2115N/A */
2115N/A public void paint(Graphics g) {
2115N/A g.clearRect(0, 0, width, height);
2115N/A }
2115N/A
2115N/A /**
2115N/A * 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
}