| /* |
| * Copyright (c) 2007, 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.java2d; |
| |
| /** |
| * This interface is used to track changes to the complex data of an |
| * object that implements the StateTrackable interface. |
| * <p> |
| * The usage pattern for code accessing the trackable data is as follows: |
| * <pre> |
| * StateTrackable trackedobject; |
| * MyInfo cacheddata; |
| * StateTracker cachetracker; |
| * public synchronized MyInfo getInfoAbout(StateTrackable obj) { |
| * if (trackedobject != obj || !cachetracker.isCurrent()) { |
| * // Note: Always call getStateTracker() before |
| * // caching any data about the objct... |
| * cachetracker = obj.getStateTracker(); |
| * cacheddata = calculateInfoFrom(obj); |
| * trackedobject = obj; |
| * } |
| * return cacheddata; |
| * } |
| * </pre> |
| * Note that the sample code above works correctly regardless of the |
| * {@link StateTrackable.State State} of the complex data of the object, |
| * but it may be inefficient to store precalculated information about |
| * an object whose current {@link StateTrackable.State State} is |
| * {@link StateTrackable.State#UNTRACKABLE UNTRACKABLE} |
| * and it is unnecessary to perform the {@link #isCurrent} test for |
| * data whose current {@link StateTrackable.State State} is |
| * {@link StateTrackable.State#IMMUTABLE IMMUTABLE}. |
| * Optimizations to the sample code for either or both of those terminal |
| * States may be of benefit for some use cases, but is left out of the |
| * example to reduce its complexity. |
| * |
| * @see StateTrackable.State |
| * @since 1.7 |
| */ |
| public interface StateTracker { |
| /** |
| * An implementation of the StateTracker interface which |
| * always returns true. |
| * This implementation is useful for objects whose current |
| * {@link StateTrackable.State State} is |
| * {@link StateTrackable.State#IMMUTABLE IMMUTABLE}. |
| * @since 1.7 |
| */ |
| public StateTracker ALWAYS_CURRENT = new StateTracker() { |
| public boolean isCurrent() { |
| return true; |
| } |
| }; |
| |
| /** |
| * An implementation of the StateTracker interface which |
| * always returns false. |
| * This implementation is useful for objects whose current |
| * {@link StateTrackable.State State} is |
| * {@link StateTrackable.State#UNTRACKABLE UNTRACKABLE}. |
| * This implementation may also be useful for some objects |
| * whose current {@link StateTrackable.State State} is |
| * {@link StateTrackable.State#DYNAMIC DYNAMIC}. |
| * @since 1.7 |
| */ |
| public StateTracker NEVER_CURRENT = new StateTracker() { |
| public boolean isCurrent() { |
| return false; |
| } |
| }; |
| |
| /** |
| * Returns true iff the contents of the complex data of the |
| * associated StateTrackable object have not changed since |
| * the time that this StateTracker was returned from its |
| * getStateTracker() method. |
| * @see StateTrackable |
| * @since 1.7 |
| */ |
| public boolean isCurrent(); |
| } |