Source for gnu.java.awt.image.AsyncImage

   1: /* AsyncImage.java -- Loads images asynchronously
   2:    Copyright (C) 2008 Free Software Foundation, Inc.
   3: 
   4: This file is part of GNU Classpath.
   5: 
   6: GNU Classpath is free software; you can redistribute it and/or modify
   7: it under the terms of the GNU General Public License as published by
   8: the Free Software Foundation; either version 2, or (at your option)
   9: any later version.
  10: 
  11: GNU Classpath is distributed in the hope that it will be useful, but
  12: WITHOUT ANY WARRANTY; without even the implied warranty of
  13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14: General Public License for more details.
  15: 
  16: You should have received a copy of the GNU General Public License
  17: along with GNU Classpath; see the file COPYING.  If not, write to the
  18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 USA.
  20: 
  21: Linking this library statically or dynamically with other modules is
  22: making a combined work based on this library.  Thus, the terms and
  23: conditions of the GNU General Public License cover the whole
  24: combination.
  25: 
  26: As a special exception, the copyright holders of this library give you
  27: permission to link this library with independent modules to produce an
  28: executable, regardless of the license terms of these independent
  29: modules, and to copy and distribute the resulting executable under
  30: terms of your choice, provided that you also meet, for each linked
  31: independent module, the terms and conditions of the license of that
  32: module.  An independent module is a module which is not derived from
  33: or based on this library.  If you modify this library, you may extend
  34: this exception to your version of the library, but you are not
  35: obligated to do so.  If you do not wish to do so, delete this
  36: exception statement from your version. */
  37: 
  38: 
  39: package gnu.java.awt.image;
  40: 
  41: 
  42: import java.awt.Graphics;
  43: import java.awt.Image;
  44: import java.awt.image.ImageConsumer;
  45: import java.awt.image.ImageObserver;
  46: import java.awt.image.ImageProducer;
  47: import java.util.HashSet;
  48: import java.util.Iterator;
  49: 
  50: /**
  51:  * Supports asynchronous loading of images.
  52:  */
  53: public class AsyncImage
  54:   extends Image
  55: {
  56: 
  57:   /**
  58:    * The image source for AsyncImages.
  59:    */
  60:   private class AsyncImageSource
  61:     implements ImageProducer
  62:   {
  63:     /**
  64:      * The real image source, if already present, or <code>null</code>
  65:      * otherwise.
  66:      */
  67:     private ImageProducer realSource;
  68: 
  69:     public void addConsumer(ImageConsumer ic)
  70:     {
  71:       startProduction(ic);
  72:     }
  73: 
  74:     public boolean isConsumer(ImageConsumer ic)
  75:     {
  76:       return false;
  77:     }
  78: 
  79:     public void removeConsumer(ImageConsumer ic)
  80:     {
  81:       // Nothing to do here.
  82:     }
  83: 
  84:     public void requestTopDownLeftRightResend(ImageConsumer ic)
  85:     {
  86:       startProduction(ic);
  87:     }
  88: 
  89:     public void startProduction(ImageConsumer ic)
  90:     {
  91:       ImageProducer ip = getRealSource();
  92:       if (ip == null)
  93:         {
  94:           ic.setDimensions(1, 1);
  95:           ic.imageComplete(ImageConsumer.SINGLEFRAMEDONE);
  96:         }
  97:       else
  98:         {
  99:           ip.startProduction(ic);
 100:         }
 101:     }
 102: 
 103:     /**
 104:      * Returns the real image source, if already present. Otherwise, this
 105:      * returns <code>null</code>.
 106:      *
 107:      * @return the real image source, or <code>null</code> if not present
 108:      */
 109:     private ImageProducer getRealSource()
 110:     {
 111:       synchronized (AsyncImage.this)
 112:         {
 113:           ImageProducer source = realSource;
 114:           if (source == null)
 115:             {
 116:               Image ri = realImage;
 117:               if (ri != null)
 118:                 {
 119:                   realSource = source = ri.getSource();
 120:                 }
 121:             }
 122:           return source;
 123:         }
 124:     }
 125:   }
 126: 
 127:   /**
 128:    * The real image. This is null as long as the image is not complete.
 129:    */
 130:   private volatile Image realImage;
 131: 
 132:   /**
 133:    * The image observers.
 134:    *
 135:    * This is package private to avoid accessor methods.
 136:    */
 137:   HashSet<ImageObserver> observers;
 138: 
 139:   private volatile boolean complete = false;
 140: 
 141:   /**
 142:    * Creates a new AsyncImage.
 143:    */
 144:   AsyncImage()
 145:   {
 146:     observers = new HashSet<ImageObserver>();
 147:   }
 148: 
 149:   public void flush()
 150:   {
 151:     // Nothing to do here.
 152:   }
 153: 
 154:   public Graphics getGraphics()
 155:   {
 156:     Image r = realImage;
 157:     Graphics g = null;
 158:     if (r != null)
 159:       g = r.getGraphics(); // Should we return some dummy graphics instead?
 160:     return g;
 161:   }
 162: 
 163:   public boolean isComplete() {
 164:         return complete;
 165:   }
 166: 
 167:   public int getHeight(ImageObserver observer)
 168:   {
 169:     addObserver(observer);
 170:     int height = -1;
 171:     waitForImage(observer);
 172:     Image r = realImage;
 173:     if (r != null)
 174:       height = r.getHeight(observer);
 175:     return height;
 176:   }
 177: 
 178:   public Object getProperty(String name, ImageObserver observer)
 179:   {
 180:     addObserver(observer);
 181:     Image r = realImage;
 182:     Object prop = null;
 183:     if (r != null)
 184:       prop = r.getProperty(name, observer);
 185:     return prop;
 186:   }
 187: 
 188:   public ImageProducer getSource()
 189:   {
 190:     return new AsyncImageSource();
 191:   }
 192: 
 193:   public int getWidth(ImageObserver observer)
 194:   {
 195:     addObserver(observer);
 196:     int width = -1;
 197:     waitForImage(observer);
 198:     Image r = realImage;
 199:     if (r != null)
 200:       width = r.getWidth(observer);
 201:     return width;
 202:   }
 203: 
 204:   public void addObserver(ImageObserver obs)
 205:   {
 206:     if (obs != null)
 207:       {
 208:         synchronized (this)
 209:           {
 210:             // This field gets null when image loading is complete and we don't
 211:             // need to store any more observers.
 212:             HashSet<ImageObserver> observs = observers;
 213:             if (observs != null)
 214:               {
 215:                 observs.add(obs);
 216:               }
 217:           }
 218:       }
 219:   }
 220: 
 221:   public boolean prepareImage(int w, int h, ImageObserver obs)
 222:   {
 223:     addObserver(obs);
 224:     return realImage != null;
 225:   }
 226: 
 227:   public int checkImage(int w, int h, ImageObserver obs)
 228:   {
 229:     addObserver(obs);
 230:     int flags = 0;
 231:     if (realImage != null)
 232:       flags = ImageObserver.ALLBITS | ImageObserver.WIDTH
 233:               | ImageObserver.HEIGHT | ImageObserver.PROPERTIES;
 234:     return flags;
 235:   }
 236: 
 237:   public Image getRealImage()
 238:   {
 239:     return realImage;
 240:   }
 241: 
 242:   public void setRealImage(Image im)
 243:   {
 244:     realImage = im;
 245:     int status = ImageObserver.HEIGHT | ImageObserver.WIDTH;
 246:     notifyObservers(status, 0, 0, im.getWidth(null), im.getHeight(null));
 247:   }
 248: 
 249:   public void notifyObservers(int status, int x, int y, int w, int h)
 250:   {
 251:     synchronized (this)
 252:     {
 253:       HashSet observs = observers;
 254:       if (observs != null)
 255:         {
 256:           Iterator i = observs.iterator();
 257:           while (i.hasNext())
 258:             {
 259:               ImageObserver obs = (ImageObserver) i.next();
 260:               boolean complete = obs.imageUpdate(this, status, x, y, realImage.getWidth(obs), realImage.getHeight(obs));
 261:               if (complete) // Remove completed observers.
 262:                 i.remove();
 263:             }
 264:         }
 265:       if ((status & ImageObserver.ALLBITS) != 0)
 266:         {
 267:           complete = true;
 268:           notifyAll();
 269:         }
 270:     }
 271:   }
 272: 
 273:   /**
 274:    * Waits for the image to be loaded completely, if the image observer
 275:    * is <code>null</code>. Otherwise this is not necessary, because the
 276:    * image observer can be notified about later completion.
 277:    *
 278:    * @param observer the image observer
 279:    */
 280:   public void waitForImage(ImageObserver observer)
 281:   {
 282:     if (!complete && observer == null)
 283:       {
 284:         synchronized (this)
 285:           {
 286:             while (! complete)
 287:               {
 288:                 try
 289:                   {
 290:                     wait();
 291:                   }
 292:                 catch (InterruptedException ex)
 293:                   {
 294:                     Thread.currentThread().interrupt();
 295:                   }
 296:               }
 297:           }
 298:       }
 299:   }
 300: }