This API provides access to the threading model for the implementation of the classes in this package.

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.

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.

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.

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.

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.

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.

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 jogl.1thread. Valid values for this system property are:

-Djogl.1thread=false     Disable single-threading of OpenGL work, hence use multithreading.
-Djogl.1thread=true      Enable single-threading of OpenGL work (default -- on a newly-created worker thread)
-Djogl.1thread=auto      Select default single-threading behavior (currently on)
-Djogl.1thread=awt       Enable single-threading of OpenGL work on AWT event dispatch thread (current default on all
                         platforms, and also the default behavior older releases)
-Djogl.1thread=worker    Enable single-threading of OpenGL work on newly-created worker thread (not suitable for Mac
                         OS X or X11 platforms, and risky on Windows in applet environments)