Created attachment 120451 [details]
Screenshots describing the problem
We are developing a freeware simulation software called Z88Aurora. The GUI is based on GTK2 and is released for Windows, Linux and OS X operating systems.
For OS X we use MacPorts to install all needed libs and then ship our software with a reduced package including the needed files only.
Everythink works fine on Linux and Windows, but on OS X we are experiencing a problem since the release of El Capitan (OS X 10.11).
The main GTK notebook page includes an OpenGL widget (gtk_gl_area) which displays the part geometry. When selecting another page, this OpenGL widget stays in front and does not disappear (cp. screenshots in attachment).
This problem only occurs on OS X El Capitan with XQuartz version 2.7.8 and 2.7.9 beta 1. XQuartz 2.7.8. works fine on OS X 10.10 and does not cause any problems with the OpenGL window.
Please let me know if this is a known error in XQuartz or where this needs to be fixed.
It's an OS X regression that I will hopefully be able to workaround in libXplugin.
Thank you for your quick response! Is it possible to announce the fix here, so I know when we can release our software for El Capitan? Or will that be mentioned in the release notes?
It'll be mentioned here and in the release notes.