Posted by gouessej on Feb 06, 2020; 9:37am
URL: https://forum.jogamp.org/Frame-with-transparent-background-tp4040332p4040339.html

It's a known concern:
https://bugs.java.com/bugdatabase/view_bug.do?bug_id=6655001

We'll need to disable HW acceleration (both OpenGL and
D3D pipelines) for non-opaque windows on systems other
than Vista.