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/*
* Copyright (c) 2003 Sun Microsystems, Inc. All Rights Reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* - Redistribution of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistribution in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* Neither the name of Sun Microsystems, Inc. or the names of
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* This software is provided "AS IS," without a warranty of any kind. ALL
* EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES,
* INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A
* PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN
* MICROSYSTEMS, INC. ("SUN") AND ITS LICENSORS SHALL NOT BE LIABLE FOR
* ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR
* DISTRIBUTING THIS SOFTWARE OR ITS DERIVATIVES. IN NO EVENT WILL SUN OR
* ITS LICENSORS BE LIABLE FOR ANY LOST REVENUE, PROFIT OR DATA, OR FOR
* DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL, INCIDENTAL OR PUNITIVE
* DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY OF LIABILITY,
* ARISING OUT OF THE USE OF OR INABILITY TO USE THIS SOFTWARE, EVEN IF
* SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
*
* You acknowledge that this software is not designed or intended for use
* in the design, construction, operation or maintenance of any nuclear
* facility.
*
* Sun gratefully acknowledges that this software was originally authored
* and developed by Kenneth Bradley Russell and Christopher John Kline.
*/
package javax.media.opengl;
import java.awt.EventQueue;
import java.lang.reflect.InvocationTargetException;
import java.security.AccessController;
import java.security.PrivilegedAction;
import com.sun.opengl.impl.*;
/** This API provides access to the threading model for the implementation of
the classes in this package.
<P>
OpenGL is specified as a thread-safe API, but in practice there
are multithreading-related issues on most, if not all, of the
platforms which support it. For example, some OpenGL
implementations do not behave well when one context is made
current first on one thread, released, and then made current on a
second thread, although this is legal according to the OpenGL
specification. On other platforms there are other problems.
<P>
Due to these limitations, and due to the inherent multithreading
in the Java platform (in particular, in the Abstract Window
Toolkit), it is often necessary to limit the multithreading
occurring in the typical application using the OpenGL API.
<P>
In the current reference implementation, for instance, multithreading
has been limited by
forcing all OpenGL-related work for GLAutoDrawables on to a single
thread. In other words, if an application uses only the
GLAutoDrawable and GLEventListener callback mechanism, it is
guaranteed to have the most correct single-threaded behavior on
all platforms.
<P>
Applications using the GLContext makeCurrent/release API directly
will inherently break this single-threaded model, as these methods
require that the OpenGL context be made current on the current
thread immediately. For applications wishing to integrate better
with an implementation that uses the single-threaded model, this
class provides public access to the mechanism used by the implementation.
<P>
Users can execute Runnables on the
internal thread used for performing OpenGL work, and query whether
the current thread is already this thread. Using these mechanisms
the user can move work from the current thread on to the internal
OpenGL thread if desired.
<P>
This class also provides mechanisms for querying whether this
internal serialization of OpenGL work is in effect, and a
programmatic way of disabling it. In the current reference
implementation it is enabled by default, although it could be
disabled in the future if OpenGL drivers become more robust on
all platforms.
<P>
In addition to specifying programmatically whether the single
thread for OpenGL work is enabled, users may switch it on and off
using the system property <code>opengl.1thread</code>. Valid values
for this system property are:
<PRE>
-Dopengl.1thread=false Disable single-threading of OpenGL work
-Dopengl.1thread=true Enable single-threading of OpenGL work (default)
-Dopengl.1thread=auto Select default single-threading behavior (currently on)
</PRE>
*/
public class Threading {
private static boolean singleThreaded = true;
static {
AccessController.doPrivileged(new PrivilegedAction() {
public Object run() {
String workaround = System.getProperty("opengl.1thread");
if (workaround != null && (!workaround.equals("auto"))) {
singleThreaded = Boolean.valueOf(workaround).booleanValue();
}
printWorkaroundNotice();
return null;
}
});
}
/** No reason to ever instantiate this class */
private Threading() {}
/** If an implementation of the javax.media.opengl APIs offers a
multithreading option but the default behavior is single-threading,
this API provides a mechanism for end users to disable single-threading
in this implementation. Users are strongly discouraged from
calling this method unless they are aware of all of the
consequences and are prepared to enforce some amount of
threading restrictions in their applications. Disabling
single-threading, for example, may have unintended consequences
on GLAutoDrawable implementations such as GLCanvas, GLJPanel and
GLPbuffer. Currently there is no supported way to re-enable it
once disabled, partly to discourage careless use of this
method. This method should be called as early as possible in an
application. */
public static void disableSingleThreading() {
singleThreaded = false;
if (Debug.verbose()) {
System.err.println("Application forced disabling of single-threading of javax.media.opengl implementation");
}
}
/** Indicates whether OpenGL work is being automatically forced to a
single thread in this implementation. */
public static boolean isSingleThreaded() {
return singleThreaded;
}
/** Indicates whether the current thread is the single thread on
which this implementation of the javax.media.opengl APIs
performs all of its OpenGL-related work. This method should only
be called if the single-thread model is in effect. */
public static boolean isOpenGLThread() throws GLException {
if (!isSingleThreaded()) {
throw new GLException("Should only call this in single-threaded mode");
}
if (Java2D.isOGLPipelineActive()) {
// FIXME: ideally only the QFT would be considered to be the
// "OpenGL thread", but we can not currently run all of JOGL's
// OpenGL work on that thread. For now, run the GLJPanel's
// Java2D/JOGL bridge on the QFT but everything else on the
// EDT, except when we're already on the QFT.
return (Java2D.isQueueFlusherThread() ||
EventQueue.isDispatchThread());
} else {
return EventQueue.isDispatchThread();
}
}
/** Executes the passed Runnable on the single thread used for all
OpenGL work in this javax.media.opengl API implementation. It is
not specified exactly which thread is used for this
purpose. This method should only be called if the single-thread
model is in use and if the current thread is not the OpenGL
thread (i.e., if <code>isOpenGLThread()</code> returns
false). It is up to the end user to check to see whether the
current thread is the OpenGL thread and either execute the
Runnable directly or perform the work inside it. */
public static void invokeOnOpenGLThread(Runnable r) throws GLException {
if (!isSingleThreaded()) {
throw new GLException ("Should only call this in single-threaded mode");
}
if (isOpenGLThread()) {
throw new GLException ("Should only call this from other threads than the OpenGL thread");
}
// FIXME: ideally should run all OpenGL work on the Java2D QFT
// thread when it's enabled, but there are issues with this when
// the GLJPanel is not using the Java2D bridge; would like to run
// its OpenGL work on the QFT, but do the image drawing from the
// EDT. Other issues still remain with the GLCanvas as well.
// if (Java2D.isOGLPipelineActive()) {
// Java2D.invokeWithOGLContextCurrent(null, r);
// } else {
try {
EventQueue.invokeAndWait(r);
} catch (InvocationTargetException e) {
throw new GLException(e.getTargetException());
} catch (InterruptedException e) {
throw new GLException(e);
}
// }
}
private static void printWorkaroundNotice() {
if (singleThreaded && Debug.verbose()) {
System.err.println("Using single thread for performing OpenGL work in javax.media.opengl implementation");
}
}
}
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