mirror of git://gcc.gnu.org/git/gcc.git
367 lines
11 KiB
Java
367 lines
11 KiB
Java
/* Canvas.java --
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Copyright (C) 1999, 2000, 2002, 2004 Free Software Foundation
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package java.awt;
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import java.awt.image.BufferStrategy;
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import java.awt.peer.ComponentPeer;
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import java.io.Serializable;
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import javax.accessibility.Accessible;
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import javax.accessibility.AccessibleContext;
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import javax.accessibility.AccessibleRole;
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/**
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* The <code>Canvas</code> component provides a blank rectangular
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* area, which the client application can use for drawing and for
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* capturing events. By overriding the <code>paint()</code> method,
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* the canvas can be used for anything from simple line drawings to
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* full-scale custom components.
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*
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* @author Original author unknown
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* @author Tom Tromey (tromey@redhat.com)
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* @author Andrew John Hughes (gnu_andrew@member.fsf.org)
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* @since 1.0
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*/
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public class Canvas
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extends Component
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implements Serializable, Accessible
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{
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/**
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* Compatible with Sun's JDK.
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*/
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private static final long serialVersionUID = -2284879212465893870L;
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/**
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* The number used to generate the name returned by getName.
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*/
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private static transient long next_canvas_number;
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/**
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* The graphics configuration associated with the canvas.
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*/
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transient GraphicsConfiguration graphicsConfiguration;
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/**
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* The buffer strategy associated with this canvas.
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*/
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transient BufferStrategy bufferStrategy;
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/**
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* Initializes a new instance of <code>Canvas</code>.
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*/
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public Canvas()
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{
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}
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/**
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* Initializes a new instance of <code>Canvas</code>
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* with the supplied graphics configuration.
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*
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* @param graphicsConfiguration the graphics configuration to use
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* for this particular canvas.
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*/
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public Canvas(GraphicsConfiguration graphicsConfiguration)
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{
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this.graphicsConfiguration = graphicsConfiguration;
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}
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GraphicsConfiguration getGraphicsConfigurationImpl()
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{
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if (graphicsConfiguration != null)
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return graphicsConfiguration;
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return super.getGraphicsConfigurationImpl();
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}
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/**
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* Creates the native peer for this object.
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*/
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public void addNotify()
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{
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if (peer == null)
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peer = (ComponentPeer) getToolkit().createCanvas(this);
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super.addNotify();
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}
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/**
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* Repaints the canvas window. This method should be overridden by
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* a subclass to do something useful, as this method simply paints
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* the window with the background color.
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*
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* @param gfx the <code>Graphics</code> to use for painting
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*/
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public void paint(Graphics gfx)
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{
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/* This implementation doesn't make much sense since the filling
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of background color is guaranteed for heavyweight components
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such as this. But there's no need to worry, since paint() is
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usually overridden anyway. */
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gfx.setColor(getBackground());
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Dimension size = getSize();
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gfx.fillRect(0, 0, size.width, size.height);
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}
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/**
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* This class provides accessibility support for the canvas.
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*/
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protected class AccessibleAWTCanvas
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extends AccessibleAWTComponent
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{
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/**
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* For compatability with Sun's JDK
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*/
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private static final long serialVersionUID = -6325592262103146699L;
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/**
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* Constructor for the accessible canvas.
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*/
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protected AccessibleAWTCanvas()
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{
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}
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/**
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* Returns the accessible role for the canvas.
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*
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* @return an instance of <code>AccessibleRole</code>, describing
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* the role of the canvas.
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*/
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public AccessibleRole getAccessibleRole()
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{
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return AccessibleRole.CANVAS;
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}
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}
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/**
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* Gets the AccessibleContext associated with this <code>Canvas</code>.
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* The context is created, if necessary.
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*
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* @return the associated context
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*/
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public AccessibleContext getAccessibleContext()
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{
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/* Create the context if this is the first request */
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if (accessibleContext == null)
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accessibleContext = new AccessibleAWTCanvas();
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return accessibleContext;
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}
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/**
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* A BltBufferStrategy for canvases.
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*/
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private class CanvasBltBufferStrategy extends BltBufferStrategy
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{
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/**
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* Creates a block transfer strategy for this canvas.
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*
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* @param numBuffers the number of buffers in this strategy
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* @param accelerated true if the buffer should be accelerated,
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* false otherwise
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*/
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CanvasBltBufferStrategy(int numBuffers, boolean accelerated)
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{
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super(numBuffers,
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new BufferCapabilities(new ImageCapabilities(accelerated),
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new ImageCapabilities(accelerated),
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BufferCapabilities.FlipContents.COPIED));
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}
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}
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/**
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* A FlipBufferStrategy for canvases.
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*/
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private class CanvasFlipBufferStrategy extends FlipBufferStrategy
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{
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/**
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* Creates a flip buffer strategy for this canvas.
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*
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* @param numBuffers the number of buffers in this strategy
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*
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* @throws AWTException if the requested number of buffers is not
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* supported
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*/
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CanvasFlipBufferStrategy(int numBuffers)
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throws AWTException
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{
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super(numBuffers,
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new BufferCapabilities(new ImageCapabilities(true),
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new ImageCapabilities(true),
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BufferCapabilities.FlipContents.COPIED));
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}
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}
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/**
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* Creates a buffering strategy that manages how this canvas is
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* repainted. This method attempts to create the optimum strategy
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* based on the desired number of buffers. Hardware or software
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* acceleration may be used.
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*
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* createBufferStrategy attempts different levels of optimization,
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* but guarantees that some strategy with the requested number of
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* buffers will be created even if it is not optimal. First it
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* attempts to create a page flipping strategy, then an accelerated
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* blitting strategy, then an unaccelerated blitting strategy.
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*
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* Calling this method causes any existing buffer strategy to be
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* destroyed.
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*
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* @param numBuffers the number of buffers in this strategy
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*
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* @throws IllegalArgumentException if requested number of buffers
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* is less than one
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* @throws IllegalStateException if this canvas is not displayable
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*
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* @since 1.4
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*/
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public void createBufferStrategy(int numBuffers)
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{
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if (numBuffers < 1)
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throw new IllegalArgumentException("Canvas.createBufferStrategy: number"
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+ " of buffers is less than one");
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if (!isDisplayable())
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throw new IllegalStateException("Canvas.createBufferStrategy: canvas is"
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+ " not displayable");
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BufferStrategy newStrategy = null;
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// try a flipping strategy
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try
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{
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newStrategy = new CanvasFlipBufferStrategy(numBuffers);
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}
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catch (AWTException e)
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{
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}
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// fall back to an accelerated blitting strategy
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if (newStrategy == null)
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newStrategy = new CanvasBltBufferStrategy(numBuffers, true);
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bufferStrategy = newStrategy;
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}
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/**
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* Creates a buffering strategy that manages how this canvas is
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* repainted. This method attempts to create a strategy based on
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* the specified capabilities and throws an exception if the
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* requested strategy is not supported.
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*
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* Calling this method causes any existing buffer strategy to be
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* destroyed.
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*
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* @param numBuffers the number of buffers in this strategy
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* @param caps the requested buffering capabilities
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*
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* @throws AWTException if the requested capabilities are not
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* supported
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* @throws IllegalArgumentException if requested number of buffers
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* is less than one or if caps is null
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*
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* @since 1.4
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*/
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public void createBufferStrategy(int numBuffers, BufferCapabilities caps)
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throws AWTException
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{
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if (numBuffers < 1)
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throw new IllegalArgumentException("Canvas.createBufferStrategy: number"
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+ " of buffers is less than one");
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if (caps == null)
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throw new IllegalArgumentException("Canvas.createBufferStrategy:"
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+ " capabilities object is null");
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// a flipping strategy was requested
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if (caps.isPageFlipping())
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bufferStrategy = new CanvasFlipBufferStrategy(numBuffers);
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else
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bufferStrategy = new CanvasBltBufferStrategy(numBuffers, true);
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}
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/**
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* Returns the buffer strategy used by the canvas.
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*
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* @return the buffer strategy.
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* @since 1.4
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*/
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public BufferStrategy getBufferStrategy()
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{
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return bufferStrategy;
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}
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/**
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* Updates the canvas in response to a request to
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* <code>repaint()</code> it. The canvas is cleared
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* with the current background colour, before <code>paint()</code>
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* is called to add the new contents. Subclasses
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* which override this method should either call this
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* method via <code>super.update(graphics)</code> or re-implement
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* this behaviour, so as to ensure that the canvas is
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* clear before painting takes place.
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*
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* @param graphics the graphics context.
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*/
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public void update(Graphics graphics)
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{
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Dimension size;
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/* Clear the canvas */
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size = getSize();
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graphics.clearRect(0, 0, size.width, size.height);
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/* Call the paint method */
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paint(graphics);
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}
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/**
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* Generate a unique name for this <code>Canvas</code>.
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*
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* @return A unique name for this <code>Canvas</code>.
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*/
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String generateName()
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{
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return "canvas" + getUniqueLong();
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}
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private static synchronized long getUniqueLong()
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{
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return next_canvas_number++;
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}
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}
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