ojluni/src/main/java/java/awt/Canvas.java - platform/libcore.git - Git at Google

 /*
  * 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
	}