Back to index...

	/*
	* Copyright (c) 2004, 2015, 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 sun.swing;

	import java.awt.*;
	import java.awt.image.*;
	import java.util.*;

	/**
	* A base class used for icons or images that are expensive to paint.
	* A subclass will do the following:
	* <ol>
	* <li>Invoke <code>paint</code> when you want to paint the image,
	* if you are implementing <code>Icon</code> you'll invoke this from
	* <code>paintIcon</code>.
	* The args argument is useful when additional state is needed.
	* <li>Override <code>paintToImage</code> to render the image. The code that
	* lives here is equivalent to what previously would go in
	* <code>paintIcon</code>, for an <code>Icon</code>.
	* </ol>
	* The two ways to use this class are:
	* <ol>
	* <li>Invoke <code>paint</code> to draw the cached reprensentation at
	* the specified location.
	* <li>Invoke <code>getImage</code> to get the cached reprensentation and
	* draw the image yourself. This is primarly useful when you are not
	* using <code>VolatileImage</code>.
	* </ol>
	*
	*
	*/
	public abstract class CachedPainter {
	// CacheMap maps from class to ImageCache.
	private static final Map<Object,ImageCache> cacheMap = new HashMap<>();

	private static ImageCache getCache(Object key) {
	synchronized(CachedPainter.class) {
	ImageCache cache = cacheMap.get(key);
	if (cache == null) {
	cache = new ImageCache(1);
	cacheMap.put(key, cache);
	}
	return cache;
	}
	}

	/**
	* Creates an instance of <code>CachedPainter</code> that will cache up
	* to <code>cacheCount</code> images of this class.
	*
	* @param cacheCount Max number of images to cache
	*/
	public CachedPainter(int cacheCount) {
	getCache(getClass()).setMaxCount(cacheCount);
	}

	/**
	* Renders the cached image to the the passed in <code>Graphic</code>.
	* If there is no cached image <code>paintToImage</code> will be invoked.
	* <code>paintImage</code> is invoked to paint the cached image.
	*
	* @param c Component rendering to, this may be null.
	* @param g Graphics to paint to
	* @param x X-coordinate to render to
	* @param y Y-coordinate to render to
	* @param w Width to render in
	* @param h Height to render in
	* @param arg Variable arguments that will be passed to paintToImage
	*/
	public void paint(Component c, Graphics g, int x,
	int y, int w, int h, Object... args) {
	if (w <= 0 \|\| h <= 0) {
	return;
	}
	synchronized (CachedPainter.class) {
	paint0(c, g, x, y, w, h, args);
	}
	}

	private void paint0(Component c, Graphics g, int x,
	int y, int w, int h, Object... args) {
	Object key = getClass();
	GraphicsConfiguration config = getGraphicsConfiguration(c);
	ImageCache cache = getCache(key);
	Image image = cache.getImage(key, config, w, h, args);
	int attempts = 0;
	do {
	boolean draw = false;
	if (image instanceof VolatileImage) {
	// See if we need to recreate the image
	switch (((VolatileImage)image).validate(config)) {
	case VolatileImage.IMAGE_INCOMPATIBLE:
	((VolatileImage)image).flush();
	image = null;
	break;
	case VolatileImage.IMAGE_RESTORED:
	draw = true;
	break;
	}
	}
	if (image == null) {
	// Recreate the image
	image = createImage(c, w, h, config, args);
	cache.setImage(key, config, w, h, args, image);
	draw = true;
	}
	if (draw) {
	// Render to the Image
	Graphics g2 = image.getGraphics();
	paintToImage(c, image, g2, w, h, args);
	g2.dispose();
	}

	// Render to the passed in Graphics
	paintImage(c, g, x, y, w, h, image, args);

	// If we did this 3 times and the contents are still lost
	// assume we're painting to a VolatileImage that is bogus and
	// give up. Presumably we'll be called again to paint.
	} while ((image instanceof VolatileImage) &&
	((VolatileImage)image).contentsLost() && ++attempts < 3);
	}

	/**
	* Paints the representation to cache to the supplied Graphics.
	*
	* @param c Component painting to, may be null.
	* @param image Image to paint to
	* @param g Graphics to paint to, obtained from the passed in Image.
	* @param w Width to paint to
	* @param h Height to paint to
	* @param args Arguments supplied to <code>paint</code>
	*/
	protected abstract void paintToImage(Component c, Image image, Graphics g,
	int w, int h, Object[] args);


	/**
	* Paints the image to the specified location.
	*
	* @param c Component painting to
	* @param g Graphics to paint to
	* @param x X coordinate to paint to
	* @param y Y coordinate to paint to
	* @param w Width to paint to
	* @param h Height to paint to
	* @param image Image to paint
	* @param args Arguments supplied to <code>paint</code>
	*/
	protected void paintImage(Component c, Graphics g,
	int x, int y, int w, int h, Image image,
	Object[] args) {
	g.drawImage(image, x, y, null);
	}

	/**
	* Creates the image to cache. This returns an opaque image, subclasses
	* that require translucency or transparency will need to override this
	* method.
	*
	* @param c Component painting to
	* @param w Width of image to create
	* @param h Height to image to create
	* @param config GraphicsConfiguration that will be
	* rendered to, this may be null.
	* @param args Arguments passed to paint
	*/
	protected Image createImage(Component c, int w, int h,
	GraphicsConfiguration config, Object[] args) {
	if (config == null) {
	return new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
	}
	return config.createCompatibleVolatileImage(w, h);
	}

	/**
	* Clear the image cache
	*/
	protected void flush() {
	synchronized(CachedPainter.class) {
	getCache(getClass()).flush();
	}
	}

	private GraphicsConfiguration getGraphicsConfiguration(Component c) {
	if (c == null) {
	return null;
	}
	return c.getGraphicsConfiguration();
	}
	}

Back to index...