Initial check-in. ImageWaiter waits for asynchronously loaded images. Derived from ImageGenerator.ImageLoader

src/helma/image/ImageWaiter.java

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+/*
+ * Helma License Notice
+ *
+ * The contents of this file are subject to the Helma License
+ * Version 2.0 (the "License"). You may not use this file except in
+ * compliance with the License. A copy of the License is available at
+ * http://adele.helma.org/download/helma/license.txt
+ *
+ * Copyright 1998-2003 Helma Software. All Rights Reserved.
+ *
+ * $RCSfile$
+ * $Author$
+ * $Revision$
+ * $Date$
+ */
+
+package helma.image;
+
+import java.awt.Image;
+
+import java.awt.image.ImageObserver;
+
+/**
+ * The ImageWaiter will only be used like this:
+ * image = ImageWaiter.waitForImage(image);
+ */
+public class ImageWaiter implements ImageObserver {
+    Image image;
+    int width;
+    int height;
+    boolean waiting;
+    boolean firstFrameLoaded;
+
+    private ImageWaiter(Image image) {
+        this.image = image;
+        waiting = true;
+        firstFrameLoaded = false;
+    }
+        
+    public static Image waitForImage(Image image) {
+        ImageWaiter waiter = new ImageWaiter(image);
+        try {
+            waiter.waitForImage();
+        } finally {
+            waiter.done();
+        }
+        return waiter.width == -1 || waiter.height == -1 ? null : image;
+    }
+
+    private synchronized void waitForImage() {
+        width = image.getWidth(this);
+        height = image.getHeight(this);
+
+        if (width == -1 || height == -1) {
+            try {
+                wait(45000);
+            } catch (InterruptedException x) {
+                waiting = false;
+                return;
+            } finally {
+                waiting = false;
+            }
+        }
+
+        // if width and height haven't been set, throw tantrum
+        if (width == -1 || height == -1) {
+            throw new RuntimeException("Error loading image");
+        }
+    }
+
+    private synchronized void done() {
+        waiting = false;
+        notifyAll();
+    }
+
+    public synchronized boolean imageUpdate(Image img, int infoflags, int x,
+        int y, int w, int h) {
+        // check if there was an error
+        if (!waiting || (infoflags & ERROR) > 0 || (infoflags & ABORT) > 0) {
+            // we either timed out or there was an error.
+            notifyAll();
+
+            return false;
+        }
+
+        if ((infoflags & WIDTH) > 0 || (infoflags & HEIGHT) > 0) {
+            if ((infoflags & WIDTH) > 0) {
+                width = w;
+            }
+
+            if ((infoflags & HEIGHT) > 0) {
+                height = h;
+            }
+
+            if (width > -1 && h > -1 && firstFrameLoaded) {
+                notifyAll();
+
+                return false;
+            }
+        }
+
+        if ((infoflags & ALLBITS) > 0 || (infoflags & FRAMEBITS) > 0) {
+            firstFrameLoaded = true;
+            notifyAll();
+
+            return false;
+        }
+
+        return true;
+    }
+}