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authorupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
committerupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
commit554fd8c5195424bdbcabf5de30fdc183aba391bd (patch)
tree976dc5ab7fddf506dadce60ae936f43f58787092 /libjava/classpath/java/awt/Canvas.java
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+/* Canvas.java --
+ Copyright (C) 1999, 2000, 2002, 2004 Free Software Foundation
+
+This file is part of GNU Classpath.
+
+GNU Classpath is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2, or (at your option)
+any later version.
+
+GNU Classpath 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 for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU Classpath; see the file COPYING. If not, write to the
+Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301 USA.
+
+Linking this library statically or dynamically with other modules is
+making a combined work based on this library. Thus, the terms and
+conditions of the GNU General Public License cover the whole
+combination.
+
+As a special exception, the copyright holders of this library give you
+permission to link this library with independent modules to produce an
+executable, regardless of the license terms of these independent
+modules, and to copy and distribute the resulting executable under
+terms of your choice, provided that you also meet, for each linked
+independent module, the terms and conditions of the license of that
+module. An independent module is a module which is not derived from
+or based on this library. If you modify this library, you may extend
+this exception to your version of the library, but you are not
+obligated to do so. If you do not wish to do so, delete this
+exception statement from your version. */
+
+
+package java.awt;
+
+import java.awt.image.BufferStrategy;
+import java.awt.peer.ComponentPeer;
+import java.io.Serializable;
+
+import javax.accessibility.Accessible;
+import javax.accessibility.AccessibleContext;
+import javax.accessibility.AccessibleRole;
+
+/**
+ * The <code>Canvas</code> component provides a blank rectangular
+ * area, which the client application can use for drawing and for
+ * capturing events. By overriding the <code>paint()</code> method,
+ * the canvas can be used for anything from simple line drawings to
+ * full-scale custom components.
+ *
+ * @author Original author unknown
+ * @author Tom Tromey (tromey@redhat.com)
+ * @author Andrew John Hughes (gnu_andrew@member.fsf.org)
+ * @since 1.0
+ */
+
+public class Canvas
+ extends Component
+ implements Serializable, Accessible
+{
+
+ /**
+ * Compatible with Sun's JDK.
+ */
+ private static final long serialVersionUID = -2284879212465893870L;
+
+ /**
+ * The number used to generate the name returned by getName.
+ */
+ private static transient long next_canvas_number;
+
+ /**
+ * The buffer strategy associated with this canvas.
+ */
+ transient BufferStrategy bufferStrategy;
+
+ /**
+ * Initializes a new instance of <code>Canvas</code>.
+ */
+ public Canvas()
+ {
+ }
+
+ /**
+ * Initializes a new instance of <code>Canvas</code>
+ * with the supplied graphics configuration.
+ *
+ * @param graphicsConfiguration the graphics configuration to use
+ * for this particular canvas.
+ */
+ public Canvas(GraphicsConfiguration graphicsConfiguration)
+ {
+ this.graphicsConfig = graphicsConfiguration;
+ }
+
+ /**
+ * Creates the native peer for this object.
+ */
+ public void addNotify()
+ {
+ if (peer == null)
+ peer = (ComponentPeer) getToolkit().createCanvas(this);
+ super.addNotify();
+ }
+
+ /**
+ * Repaints the canvas window. This method should be overridden by
+ * a subclass to do something useful, as this method simply paints
+ * the window with the background color.
+ *
+ * @param gfx the <code>Graphics</code> to use for painting
+ */
+ public void paint(Graphics gfx)
+ {
+ /* This implementation doesn't make much sense since the filling
+ of background color is guaranteed for heavyweight components
+ such as this. But there's no need to worry, since paint() is
+ usually overridden anyway. */
+ gfx.setColor(getBackground());
+ Dimension size = getSize();
+ gfx.fillRect(0, 0, size.width, size.height);
+ }
+
+ /**
+ * This class provides accessibility support for the canvas.
+ */
+ protected class AccessibleAWTCanvas
+ extends AccessibleAWTComponent
+ {
+ /**
+ * For compatability with Sun's JDK
+ */
+ private static final long serialVersionUID = -6325592262103146699L;
+
+ /**
+ * Constructor for the accessible canvas.
+ */
+ protected AccessibleAWTCanvas()
+ {
+ }
+
+ /**
+ * Returns the accessible role for the canvas.
+ *
+ * @return an instance of <code>AccessibleRole</code>, describing
+ * the role of the canvas.
+ */
+ public AccessibleRole getAccessibleRole()
+ {
+ return AccessibleRole.CANVAS;
+ }
+
+ }
+
+ /**
+ * Gets the AccessibleContext associated with this <code>Canvas</code>.
+ * The context is created, if necessary.
+ *
+ * @return the associated context
+ */
+ public AccessibleContext getAccessibleContext()
+ {
+ /* Create the context if this is the first request */
+ if (accessibleContext == null)
+ accessibleContext = new AccessibleAWTCanvas();
+ return accessibleContext;
+ }
+
+ /**
+ * A BltBufferStrategy for canvases.
+ */
+ private class CanvasBltBufferStrategy extends BltBufferStrategy
+ {
+ /**
+ * Creates a block transfer strategy for this canvas.
+ *
+ * @param numBuffers the number of buffers in this strategy
+ * @param accelerated true if the buffer should be accelerated,
+ * false otherwise
+ */
+ CanvasBltBufferStrategy(int numBuffers, boolean accelerated)
+ {
+ super(numBuffers,
+ new BufferCapabilities(new ImageCapabilities(accelerated),
+ new ImageCapabilities(accelerated),
+ BufferCapabilities.FlipContents.COPIED));
+ }
+ }
+
+ /**
+ * A FlipBufferStrategy for canvases.
+ */
+ private class CanvasFlipBufferStrategy extends FlipBufferStrategy
+ {
+ /**
+ * Creates a flip buffer strategy for this canvas.
+ *
+ * @param numBuffers the number of buffers in this strategy
+ *
+ * @throws AWTException if the requested number of buffers is not
+ * supported
+ */
+ CanvasFlipBufferStrategy(int numBuffers)
+ throws AWTException
+ {
+ super(numBuffers,
+ new BufferCapabilities(new ImageCapabilities(true),
+ new ImageCapabilities(true),
+ BufferCapabilities.FlipContents.COPIED));
+ }
+ }
+
+ /**
+ * Creates a buffering strategy that manages how this canvas is
+ * repainted. This method attempts to create the optimum strategy
+ * based on the desired number of buffers. Hardware or software
+ * acceleration may be used.
+ *
+ * createBufferStrategy attempts different levels of optimization,
+ * but guarantees that some strategy with the requested number of
+ * buffers will be created even if it is not optimal. First it
+ * attempts to create a page flipping strategy, then an accelerated
+ * blitting strategy, then an unaccelerated blitting strategy.
+ *
+ * Calling this method causes any existing buffer strategy to be
+ * destroyed.
+ *
+ * @param numBuffers the number of buffers in this strategy
+ *
+ * @throws IllegalArgumentException if requested number of buffers
+ * is less than one
+ * @throws IllegalStateException if this canvas is not displayable
+ *
+ * @since 1.4
+ */
+ public void createBufferStrategy(int numBuffers)
+ {
+ if (numBuffers < 1)
+ throw new IllegalArgumentException("Canvas.createBufferStrategy: number"
+ + " of buffers is less than one");
+
+ if (!isDisplayable())
+ throw new IllegalStateException("Canvas.createBufferStrategy: canvas is"
+ + " not displayable");
+
+ BufferStrategy newStrategy = null;
+
+ // try a flipping strategy
+ try
+ {
+ newStrategy = new CanvasFlipBufferStrategy(numBuffers);
+ }
+ catch (AWTException e)
+ {
+ }
+
+ // fall back to an accelerated blitting strategy
+ if (newStrategy == null)
+ newStrategy = new CanvasBltBufferStrategy(numBuffers, true);
+
+ bufferStrategy = newStrategy;
+ }
+
+ /**
+ * Creates a buffering strategy that manages how this canvas is
+ * repainted. This method attempts to create a strategy based on
+ * the specified capabilities and throws an exception if the
+ * requested strategy is not supported.
+ *
+ * Calling this method causes any existing buffer strategy to be
+ * destroyed.
+ *
+ * @param numBuffers the number of buffers in this strategy
+ * @param caps the requested buffering capabilities
+ *
+ * @throws AWTException if the requested capabilities are not
+ * supported
+ * @throws IllegalArgumentException if requested number of buffers
+ * is less than one or if caps is null
+ *
+ * @since 1.4
+ */
+ public void createBufferStrategy(int numBuffers, BufferCapabilities caps)
+ throws AWTException
+ {
+ if (numBuffers < 1)
+ throw new IllegalArgumentException("Canvas.createBufferStrategy: number"
+ + " of buffers is less than one");
+
+ if (caps == null)
+ throw new IllegalArgumentException("Canvas.createBufferStrategy:"
+ + " capabilities object is null");
+
+ // a flipping strategy was requested
+ if (caps.isPageFlipping())
+ bufferStrategy = new CanvasFlipBufferStrategy(numBuffers);
+ else
+ bufferStrategy = new CanvasBltBufferStrategy(numBuffers, true);
+ }
+
+ /**
+ * Returns the buffer strategy used by the canvas.
+ *
+ * @return the buffer strategy.
+ * @since 1.4
+ */
+ public BufferStrategy getBufferStrategy()
+ {
+ return bufferStrategy;
+ }
+
+ /**
+ * Updates the canvas in response to a request to
+ * <code>repaint()</code> it. The canvas is cleared
+ * with the current background colour, before <code>paint()</code>
+ * is called to add the new contents. Subclasses
+ * which override this method should either call this
+ * method via <code>super.update(graphics)</code> or re-implement
+ * this behaviour, so as to ensure that the canvas is
+ * clear before painting takes place.
+ *
+ * @param graphics the graphics context.
+ */
+ public void update(Graphics graphics)
+ {
+ Dimension size;
+
+ /* Clear the canvas */
+ size = getSize();
+ graphics.clearRect(0, 0, size.width, size.height);
+ /* Call the paint method */
+ paint(graphics);
+ }
+
+ /**
+ * Generate a unique name for this <code>Canvas</code>.
+ *
+ * @return A unique name for this <code>Canvas</code>.
+ */
+ String generateName()
+ {
+ return "canvas" + getUniqueLong();
+ }
+
+ private static synchronized long getUniqueLong()
+ {
+ return next_canvas_number++;
+ }
+}