| /* |
| * Copyright (c) 1995, 2012, 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.awt.image; |
| |
| import java.lang.ref.WeakReference; |
| import java.awt.Image; |
| import java.awt.image.ImageObserver; |
| |
| import java.security.AccessControlContext; |
| import java.security.AccessController; |
| import java.security.PrivilegedAction; |
| |
| public abstract class ImageWatched { |
| public static Link endlink = new Link(); |
| |
| public Link watcherList; |
| |
| public ImageWatched() { |
| watcherList = endlink; |
| } |
| |
| /* |
| * This class defines a node on a linked list of ImageObservers. |
| * The base class defines the dummy implementation used for the |
| * last link on all chains and a subsequent subclass then |
| * defines the standard implementation that manages a weak |
| * reference to a real ImageObserver. |
| */ |
| public static class Link { |
| /* |
| * Check if iw is the referent of this Link or any |
| * subsequent Link objects on this chain. |
| */ |
| public boolean isWatcher(ImageObserver iw) { |
| return false; // No "iw" down here. |
| } |
| |
| /* |
| * Remove this Link from the chain if its referent |
| * is the indicated target or if it has been nulled |
| * out by the garbage collector. |
| * Return the new remainder of the chain. |
| * The argument may be null which will trigger |
| * the chain to remove only the dead (null) links. |
| * This method is only ever called inside a |
| * synchronized block so Link.next modifications |
| * will be safe. |
| */ |
| public Link removeWatcher(ImageObserver iw) { |
| return this; // Leave me as the end link. |
| } |
| |
| /* |
| * Deliver the indicated image update information |
| * to the referent of this Link and return a boolean |
| * indicating whether or not some referent became |
| * null or has indicated a lack of interest in |
| * further updates to its imageUpdate() method. |
| * This method is not called inside a synchronized |
| * block so Link.next modifications are not safe. |
| */ |
| public boolean newInfo(Image img, int info, |
| int x, int y, int w, int h) |
| { |
| return false; // No disinterested parties down here. |
| } |
| } |
| |
| static class AccWeakReference<T> extends WeakReference<T> { |
| |
| private final AccessControlContext acc; |
| |
| AccWeakReference(T ref) { |
| super(ref); |
| acc = AccessController.getContext(); |
| } |
| } |
| |
| /* |
| * Standard Link implementation to manage a Weak Reference |
| * to an ImageObserver. |
| */ |
| public static class WeakLink extends Link { |
| private final AccWeakReference<ImageObserver> myref; |
| private Link next; |
| |
| public WeakLink(ImageObserver obs, Link next) { |
| myref = new AccWeakReference<ImageObserver>(obs); |
| this.next = next; |
| } |
| |
| public boolean isWatcher(ImageObserver iw) { |
| return (myref.get() == iw || next.isWatcher(iw)); |
| } |
| |
| public Link removeWatcher(ImageObserver iw) { |
| ImageObserver myiw = myref.get(); |
| if (myiw == null) { |
| // Remove me from the chain, but continue recursion. |
| return next.removeWatcher(iw); |
| } |
| // At this point myiw is not null so we know this test will |
| // never succeed if this is a pruning pass (iw == null). |
| if (myiw == iw) { |
| // Remove me from the chain and end the recursion here. |
| return next; |
| } |
| // I am alive, but not the one to be removed, recurse |
| // and update my next link and leave me in the chain. |
| next = next.removeWatcher(iw); |
| return this; |
| } |
| |
| private static boolean update(ImageObserver iw, AccessControlContext acc, |
| Image img, int info, |
| int x, int y, int w, int h) { |
| |
| if (acc != null || System.getSecurityManager() != null) { |
| return AccessController.doPrivileged( |
| (PrivilegedAction<Boolean>) () -> { |
| return iw.imageUpdate(img, info, x, y, w, h); |
| }, acc); |
| } |
| return false; |
| } |
| |
| public boolean newInfo(Image img, int info, |
| int x, int y, int w, int h) |
| { |
| // Note tail recursion because items are added LIFO. |
| boolean ret = next.newInfo(img, info, x, y, w, h); |
| ImageObserver myiw = myref.get(); |
| if (myiw == null) { |
| // My referent is null so we must prune in a second pass. |
| ret = true; |
| } else if (update(myiw, myref.acc, img, info, x, y, w, h) == false) { |
| // My referent has lost interest so clear it and ask |
| // for a pruning pass to remove it later. |
| myref.clear(); |
| ret = true; |
| } |
| return ret; |
| } |
| } |
| |
| public synchronized void addWatcher(ImageObserver iw) { |
| if (iw != null && !isWatcher(iw)) { |
| watcherList = new WeakLink(iw, watcherList); |
| } |
| watcherList = watcherList.removeWatcher(null); |
| } |
| |
| public synchronized boolean isWatcher(ImageObserver iw) { |
| return watcherList.isWatcher(iw); |
| } |
| |
| public void removeWatcher(ImageObserver iw) { |
| synchronized (this) { |
| watcherList = watcherList.removeWatcher(iw); |
| } |
| if (watcherList == endlink) { |
| notifyWatcherListEmpty(); |
| } |
| } |
| |
| public boolean isWatcherListEmpty() { |
| synchronized (this) { |
| watcherList = watcherList.removeWatcher(null); |
| } |
| return (watcherList == endlink); |
| } |
| |
| public void newInfo(Image img, int info, int x, int y, int w, int h) { |
| if (watcherList.newInfo(img, info, x, y, w, h)) { |
| // Some Link returned true so we now need to prune dead links. |
| removeWatcher(null); |
| } |
| } |
| |
| protected abstract void notifyWatcherListEmpty(); |
| } |