1 files changed, 121 insertions, 0 deletions
diff --git a/src/share/classes/sun/awt/image/VSyncedBSManager.java b/src/share/classes/sun/awt/image/VSyncedBSManager.java
new file mode 100644
index 000000000..2a072e3ed
--- /dev/null
+++ b/src/share/classes/sun/awt/image/VSyncedBSManager.java
@@ -0,0 +1,121 @@
+/*
+ * Copyright 2007-2008 Sun Microsystems, Inc.  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.  Sun designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ */
+
+package sun.awt.image;
+
+import java.awt.image.BufferStrategy;
+import java.lang.ref.WeakReference;
+
+/**
+ * Manages v-synced buffer strategies.
+ */
+public abstract class VSyncedBSManager {
+
+    private static VSyncedBSManager theInstance;
+
+    private static final boolean vSyncLimit =
+        Boolean.valueOf((String)java.security.AccessController.doPrivileged(
+                new sun.security.action.GetPropertyAction(
+                    "sun.java2d.vsynclimit", "true")));
+
+    private static VSyncedBSManager getInstance(boolean create) {
+        if (theInstance == null && create) {
+            theInstance =
+                vSyncLimit ? new SingleVSyncedBSMgr() : new NoLimitVSyncBSMgr();
+        }
+        return theInstance;
+    }
+
+    abstract boolean checkAllowed(BufferStrategy bs);
+    abstract void relinquishVsync(BufferStrategy bs);
+
+    /**
+     * Returns true if the buffer strategy is allowed to be created
+     * v-synced.
+     *
+     * @return true if the bs is allowed to be v-synced, false otherwise
+     */
+    public static boolean vsyncAllowed(BufferStrategy bs) {
+        VSyncedBSManager bsm = getInstance(true);
+        return bsm.checkAllowed(bs);
+    }
+
+    /**
+     * Lets the manager know that this buffer strategy is no longer interested
+     * in being v-synced.
+     */
+    public static synchronized void releaseVsync(BufferStrategy bs) {
+        VSyncedBSManager bsm = getInstance(false);
+        if (bsm != null) {
+            bsm.relinquishVsync(bs);
+        }
+    }
+
+    /**
+     * An instance of the manager which allows any buffer strategy to be
+     * v-synced.
+     */
+    private static final class NoLimitVSyncBSMgr extends VSyncedBSManager {
+        @Override
+        boolean checkAllowed(BufferStrategy bs) {
+            return true;
+        }
+
+        @Override
+        void relinquishVsync(BufferStrategy bs) {
+        }
+    }
+
+    /**
+     * An instance of the manager which allows only one buffer strategy to
+     * be v-synced at any give moment in the vm.
+     */
+    private static final class SingleVSyncedBSMgr extends VSyncedBSManager {
+        private WeakReference<BufferStrategy> strategy;
+
+        @Override
+        public synchronized boolean checkAllowed(BufferStrategy bs) {
+            if (strategy != null) {
+                BufferStrategy current = strategy.get();
+                if (current != null) {
+                    return (current == bs);
+                }
+            }
+            strategy = new WeakReference<BufferStrategy>(bs);
+            return true;
+        }
+
+        @Override
+        public synchronized void relinquishVsync(BufferStrategy bs) {
+            if (strategy != null) {
+                BufferStrategy b = strategy.get();
+                if (b == bs) {
+                    strategy.clear();
+                    strategy = null;
+                }
+            }
+        }
+    }
+}