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1   /*
2    * Copyright (c) 2007, Oracle and/or its affiliates. All rights reserved.
3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4    *
5    * This code is free software; you can redistribute it and/or modify it
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7    * published by the Free Software Foundation.  Oracle designates this
8    * particular file as subject to the "Classpath" exception as provided
9    * by Oracle in the LICENSE file that accompanied this code.
10   *
11   * This code is distributed in the hope that it will be useful, but WITHOUT
12   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14   * version 2 for more details (a copy is included in the LICENSE file that
15   * accompanied this code).
16   *
17   * You should have received a copy of the GNU General Public License version
18   * 2 along with this work; if not, write to the Free Software Foundation,
19   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20   *
21   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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24   */
25  
26  package sun.java2d;
27  
28  import sun.java2d.StateTrackable.State;
29  import static sun.java2d.StateTrackable.State.*;
30  
31  /**
32   * This class provides a basic pre-packaged implementation of the
33   * complete {@link StateTrackable} interface with implementations
34   * of the required methods in the interface and methods to manage
35   * transitions in the state of the object.
36   * Classes which wish to implement StateTrackable could create an
37   * instance of this class and delegate all of their implementations
38   * for {@code StateTrackable} methods to the corresponding methods
39   * of this class.
40   */
41  public final class StateTrackableDelegate implements StateTrackable {
42      /**
43       * The {@code UNTRACKABLE_DELEGATE} provides an implementation
44       * of the StateTrackable interface that is permanently in the
45       * {@link State#UNTRACKABLE UNTRACKABLE} state.
46       */
47      public final static StateTrackableDelegate UNTRACKABLE_DELEGATE =
48          new StateTrackableDelegate(UNTRACKABLE);
49  
50      /**
51       * The {@code IMMUTABLE_DELEGATE} provides an implementation
52       * of the StateTrackable interface that is permanently in the
53       * {@link State#IMMUTABLE IMMUTABLE} state.
54       */
55      public final static StateTrackableDelegate IMMUTABLE_DELEGATE =
56          new StateTrackableDelegate(IMMUTABLE);
57  
58      /**
59       * Returns a {@code StateTrackableDelegate} instance with the
60       * specified initial {@link State State}.
61       * If the specified {@code State} is
62       * {@link State#UNTRACKABLE UNTRACKABLE} or
63       * {@link State#IMMUTABLE IMMUTABLE}
64       * then the approprirate static instance
65       * {@link #UNTRACKABLE_DELEGATE} or {@link #IMMUTABLE_DELEGATE}
66       * is returned.
67       */
68      public static StateTrackableDelegate createInstance(State state) {
69          switch (state) {
70          case UNTRACKABLE:
71              return UNTRACKABLE_DELEGATE;
72          case STABLE:
73              return new StateTrackableDelegate(STABLE);
74          case DYNAMIC:
75              return new StateTrackableDelegate(DYNAMIC);
76          case IMMUTABLE:
77              return IMMUTABLE_DELEGATE;
78          default:
79              throw new InternalError("unknown state");
80          }
81      }
82  
83      private State theState;
84      StateTracker theTracker;   // package private for easy access from tracker
85      private int numDynamicAgents;
86  
87      /**
88       * Constructs a StateTrackableDelegate object with the specified
89       * initial State.
90       */
91      private StateTrackableDelegate(State state) {
92          this.theState = state;
93      }
94  
95      /**
96       * @inheritDoc
97       * @since 1.7
98       */
99      public State getState() {
100         return theState;
101     }
102 
103     /**
104      * @inheritDoc
105      * @since 1.7
106      */
107     public synchronized StateTracker getStateTracker() {
108         StateTracker st = theTracker;
109         if (st == null) {
110             switch (theState) {
111             case IMMUTABLE:
112                 st = StateTracker.ALWAYS_CURRENT;
113                 break;
114             case STABLE:
115                 st = new StateTracker() {
116                     public boolean isCurrent() {
117                         return (theTracker == this);
118                     }
119                 };
120                 break;
121             case DYNAMIC:
122                 // We return the NEVER_CURRENT tracker, but that is
123                 // just temporary while we are in the DYNAMIC state.
124                 // NO BREAK
125             case UNTRACKABLE:
126                 st = StateTracker.NEVER_CURRENT;
127                 break;
128             }
129             theTracker = st;
130         }
131         return st;
132     }
133 
134     /**
135      * This method provides an easy way for delegating classes to
136      * change the overall {@link State State} of the delegate to
137      * {@link State#IMMUTABLE IMMUTABLE}.
138      * @throws IllegalStateException if the current state is
139      *         {@link State#UNTRACKABLE UNTRACKABLE}
140      * @see #setUntrackable
141      * @since 1.7
142      */
143     public synchronized void setImmutable() {
144         if (theState == UNTRACKABLE || theState == DYNAMIC) {
145             throw new IllegalStateException("UNTRACKABLE or DYNAMIC "+
146                                             "objects cannot become IMMUTABLE");
147         }
148         theState = IMMUTABLE;
149         theTracker = null;
150     }
151 
152     /**
153      * This method provides an easy way for delegating classes to
154      * change the overall {@link State State} of the delegate to
155      * {@link State#UNTRACKABLE UNTRACKABLE}.
156      * This method is typically called when references to the
157      * internal data buffers have been made public.
158      * @throws IllegalStateException if the current state is
159      *         {@link State#IMMUTABLE IMMUTABLE}
160      * @see #setImmutable
161      * @since 1.7
162      */
163     public synchronized void setUntrackable() {
164         if (theState == IMMUTABLE) {
165             throw new IllegalStateException("IMMUTABLE objects cannot "+
166                                             "become UNTRACKABLE");
167         }
168         theState = UNTRACKABLE;
169         theTracker = null;
170     }
171 
172     /**
173      * This method provides an easy way for delegating classes to
174      * manage temporarily setting the overall {@link State State}
175      * of the delegate to {@link State#DYNAMIC DYNAMIC}
176      * during well-defined time frames of dynamic pixel updating.
177      * This method should be called once before each flow of control
178      * that might dynamically update the pixels in an uncontrolled
179      * or unpredictable fashion.
180      * <p>
181      * The companion method {@link #removeDynamicAgent} method should
182      * also be called once after each such flow of control has ended.
183      * Failing to call the remove method will result in this object
184      * permanently becoming {@link State#DYNAMIC DYNAMIC}
185      * and therefore effectively untrackable.
186      * <p>
187      * This method will only change the {@link State State} of the
188      * delegate if it is currently {@link State#STABLE STABLE}.
189      *
190      * @throws IllegalStateException if the current state is
191      *         {@link State#IMMUTABLE IMMUTABLE}
192      * @since 1.7
193      */
194     public synchronized void addDynamicAgent() {
195         if (theState == IMMUTABLE) {
196             throw new IllegalStateException("Cannot change state from "+
197                                             "IMMUTABLE");
198         }
199         ++numDynamicAgents;
200         if (theState == STABLE) {
201             theState = DYNAMIC;
202             theTracker = null;
203         }
204     }
205 
206     /**
207      * This method provides an easy way for delegating classes to
208      * manage restoring the overall {@link State State} of the
209      * delegate back to {@link State#STABLE STABLE}
210      * after a well-defined time frame of dynamic pixel updating.
211      * This method should be called once after each flow of control
212      * that might dynamically update the pixels in an uncontrolled
213      * or unpredictable fashion has ended.
214      * <p>
215      * The companion method {@link #addDynamicAgent} method should
216      * have been called at some point before each such flow of
217      * control began.
218      * If this method is called without having previously called
219      * the add method, the {@link State State} of this object
220      * will become unreliable.
221      * <p>
222      * This method will only change the {@link State State} of the
223      * delegate if the number of outstanding dynamic agents has
224      * gone to 0 and it is currently
225      * {@link State#DYNAMIC DYNAMIC}.
226      *
227      * @since 1.7
228      */
229     protected synchronized void removeDynamicAgent() {
230         if (--numDynamicAgents == 0 && theState == DYNAMIC) {
231             theState = STABLE;
232             theTracker = null;
233         }
234     }
235 
236     /**
237      * This method provides an easy way for delegating classes to
238      * indicate that the contents have changed.
239      * This method will invalidate outstanding StateTracker objects
240      * so that any other agents which maintain cached information
241      * about the pixels will know to refresh their cached copies.
242      * This method should be called after every modification to
243      * the data, such as any calls to any of the setElem methods.
244      * <p>
245      * Note that, for efficiency, this method does not check the
246      * {@link State State} of the object to see if it is compatible
247      * with being marked dirty
248      * (i.e. not {@link State#IMMUTABLE IMMUTABLE}).
249      * It is up to the callers to enforce the fact that an
250      * {@code IMMUTABLE} delegate is never modified.
251      * @since 1.7
252      */
253     public final void markDirty() {
254         theTracker = null;
255     }
256 }