1 /*
2 * Copyright (c) 2005, 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
6 * under the terms of the GNU General Public License version 2 only, as
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
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package sun.java2d.pipe;
27
28 import java.util.HashSet;
29 import java.util.Set;
30 import sun.awt.SunToolkit;
31
32 /**
33 * The RenderQueue class encapsulates a RenderBuffer on which rendering
34 * operations are enqueued. Note that the RenderQueue lock must be acquired
35 * before performing any operations on the queue (e.g. enqueuing an operation
36 * or flushing the queue). A sample usage scenario follows:
37 *
38 * public void drawSomething(...) {
39 * rq.lock();
40 * try {
41 * ctx.validate(...);
42 * rq.ensureCapacity(4);
43 * rq.getBuffer().putInt(DRAW_SOMETHING);
44 * ...
45 * } finally {
46 * rq.unlock();
47 * }
48 * }
49 *
50 * If you are enqueuing an operation that involves 8-byte parameters (i.e.
51 * long or double values), it is imperative that you ensure proper
52 * alignment of the underlying RenderBuffer. This can be accomplished
53 * simply by providing an offset to the first 8-byte parameter in your
54 * operation to the ensureCapacityAndAlignment() method. For example:
55 *
56 * public void drawStuff(...) {
57 * rq.lock();
58 * try {
59 * RenderBuffer buf = rq.getBuffer();
60 * ctx.validate(...);
61 * // 28 total bytes in the operation, 12 bytes to the first long
62 * rq.ensureCapacityAndAlignment(28, 12);
63 * buf.putInt(DRAW_STUFF);
64 * buf.putInt(x).putInt(y);
65 * buf.putLong(addr1);
66 * buf.putLong(addr2);
67 * } finally {
68 * rq.unlock();
69 * }
70 * }
71 */
72 public abstract class RenderQueue {
73
74 /** The size of the underlying buffer, in bytes. */
75 private static final int BUFFER_SIZE = 32000;
76
77 /** The underlying buffer for this queue. */
78 protected RenderBuffer buf;
79
80 /**
81 * A Set containing hard references to Objects that must stay alive until
82 * the queue has been completely flushed.
83 */
84 protected Set<Object> refSet;
85
86 protected RenderQueue() {
87 refSet = new HashSet<>();
88 buf = RenderBuffer.allocate(BUFFER_SIZE);
89 }
90
91 /**
92 * Locks the queue for read/write access.
93 */
94 public final void lock() {
95 /*
96 * Implementation note: In theory we should have two separate locks:
97 * one lock to synchronize access to the RenderQueue, and then a
98 * separate lock (the AWT lock) that only needs to be acquired when
99 * we are about to flush the queue (using native windowing system
100 * operations). In practice it has been difficult to enforce the
101 * correct lock ordering; sometimes AWT will have already acquired
102 * the AWT lock before grabbing the RQ lock (see 6253009), while the
103 * expected order should be RQ lock and then AWT lock. Due to this
104 * issue, using two separate locks is prone to deadlocks. Therefore,
105 * to solve this issue we have decided to eliminate the separate RQ
106 * lock and instead just acquire the AWT lock here. (Someday it might
107 * be nice to go back to the old two-lock system, but that would
108 * require potentially risky changes to AWT to ensure that it never
109 * acquires the AWT lock before calling into 2D code that wants to
110 * acquire the RQ lock.)
111 */
112 SunToolkit.awtLock();
113 }
114
115 /**
116 * Attempts to lock the queue. If successful, this method returns true,
117 * indicating that the caller is responsible for calling
118 * <code>unlock</code>; otherwise this method returns false.
119 */
120 public final boolean tryLock() {
121 return SunToolkit.awtTryLock();
122 }
123
124 /**
125 * Unlocks the queue.
126 */
127 public final void unlock() {
128 SunToolkit.awtUnlock();
129 }
130
131 /**
132 * Adds the given Object to the set of hard references, which will
133 * prevent that Object from being disposed until the queue has been
134 * flushed completely. This is useful in cases where some enqueued
135 * data could become invalid if the reference Object were garbage
136 * collected before the queue could be processed. (For example, keeping
137 * a hard reference to a FontStrike will prevent any enqueued glyph
138 * images associated with that strike from becoming invalid before the
139 * queue is flushed.) The reference set will be cleared immediately
140 * after the queue is flushed each time.
141 */
142 public final void addReference(Object ref) {
143 refSet.add(ref);
144 }
145
146 /**
147 * Returns the encapsulated RenderBuffer object.
148 */
149 public final RenderBuffer getBuffer() {
150 return buf;
151 }
152
153 /**
154 * Ensures that there will be enough room on the underlying buffer
155 * for the following operation. If the operation will not fit given
156 * the remaining space, the buffer will be flushed immediately, leaving
157 * an empty buffer for the impending operation.
158 *
159 * @param opsize size (in bytes) of the following operation
160 */
161 public final void ensureCapacity(int opsize) {
162 if (buf.remaining() < opsize) {
163 flushNow();
164 }
165 }
166
167 /**
168 * Convenience method that is equivalent to calling ensureCapacity()
169 * followed by ensureAlignment(). The ensureCapacity() call allows for an
170 * extra 4 bytes of space in case the ensureAlignment() method needs to
171 * insert a NOOP token on the buffer.
172 *
173 * @param opsize size (in bytes) of the following operation
174 * @param first8ByteValueOffset offset (in bytes) from the current
175 * position to the first 8-byte value used in the following operation
176 */
177 public final void ensureCapacityAndAlignment(int opsize,
178 int first8ByteValueOffset)
179 {
180 ensureCapacity(opsize + 4);
181 ensureAlignment(first8ByteValueOffset);
182 }
183
184 /**
185 * Inserts a 4-byte NOOP token when necessary to ensure that all 8-byte
186 * parameters for the following operation are added to the underlying
187 * buffer with an 8-byte memory alignment.
188 *
189 * @param first8ByteValueOffset offset (in bytes) from the current
190 * position to the first 8-byte value used in the following operation
191 */
192 public final void ensureAlignment(int first8ByteValueOffset) {
193 int first8ByteValuePosition = buf.position() + first8ByteValueOffset;
194 if ((first8ByteValuePosition & 7) != 0) {
195 buf.putInt(BufferedOpCodes.NOOP);
196 }
197 }
198
199 /**
200 * Immediately processes each operation currently pending on the buffer.
201 * This method will block until the entire buffer has been flushed. The
202 * queue lock must be acquired before calling this method.
203 */
204 public abstract void flushNow();
205
206 /**
207 * Immediately processes each operation currently pending on the buffer,
208 * and then invokes the provided task. This method will block until the
209 * entire buffer has been flushed and the provided task has been executed.
210 * The queue lock must be acquired before calling this method.
211 */
212 public abstract void flushAndInvokeNow(Runnable task);
213
214 /**
215 * Updates the current position of the underlying buffer, and then
216 * flushes the queue immediately. This method is useful when native code
217 * has added data to the queue and needs to flush immediately.
218 */
219 public void flushNow(int position) {
220 buf.position(position);
221 flushNow();
222 }
223 }