gldata.doubleBuffer = true;
// need SWT.NO_BACKGROUND to prevent SWT from clearing the window
// at the wrong times (we use glClear for this instead)
final GLCanvas glcanvas = new GLCanvas( composite, SWT.NO_BACKGROUND, gldata );
glcanvas.setCurrent();
GLProfile glprofile = GLProfile.getDefault();
final GLContext glcontext = GLDrawableFactory.getFactory( glprofile ).createExternalGLContext();
// fix the viewport when the user resizes the window
glcanvas.addListener( SWT.Resize, new Listener() {
public void handleEvent(Event event) {