Egon, have you ever run into the problem with AWTGLCanvas in which the entire rendering is out of place on the canvas that I did about a decade ago and ever since on every computer I've ever run my stuff on? I'd love to have that fixed (most likely by switching to lwjgl 3 and convincing them to add AWTGLCanvas back). What do you think?
I've moved the question into a new topic, just in case you are wondering.
I'm not aware of a problem with the location of AWTGLCanvas but then again, I've never really used it in situations where it doesn't use the whole frame. So I never tried to use it as part of an actual UI.
Have to tried to disable Java2D's accelerated rendering pipeline? Maybe it's a problem with that (albeit I doubt it, but it might be worth a try).
I've tried everything. Test it out as an actual UI and let me know, please.
Although I should reiterate that I usually use it on the entire frame. I'm making a sometimes-2d sometimes 3d game and it would be available there.