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/*
* 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;
}
}
}
}
}
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