Java2D GL rendering pipeline + GLJPanel + FBOs

I’m working on a Desktop JOGL app that uses GLJPanel with FBO + depth texture for shadow maps. There is also an alternative low res shadow rendering path using the back buffer if no FBOs are available.

It all works fine until I turn on the Java2D OpenGL rendering path with -Dsun.java2d.opengl=True. Then the GLJPanel is cleared to the correct color, but no other drawing occurs. No errors are reported with a DebugGL in place.

If I force the low res path that avoids the FBO extension, it all starts working again.

So it looks like there is some incompatibility with the Java2D OpenGL + GLJPanel + FBO combination.

All ideas appreciated. Happy to post code if that will be useful.