Trouble shooting

Using OpenGL through ssh

Some widgets in silx.gui are using OpenGL2.1:

• Widgets in silx.gui.plot3d, and

• The OpenGL backend of PlotWidget and related widgets in silx.gui.plot.

When running applications based on OpenGL2.1 through ssh, there are a few situations that can prevent the display of OpenGL widgets:

• Make sure to use ssh -X to enable X11 forwarding.

• OpenGL is disabled with X11 forwarding (the default on Debian). See Enabling OpenGL forwarding.

• Unless the operating system is using libglvnd (available from Debian 9 backports onward), both the server and the client computers must have the same kind of GPU drivers (either both using proprietary NVidia drivers or both using open source drivers), otherwise only OpenGL1.4 is available.

To get the currently available version of OpenGL, run from the command line:

glxinfo | grep "OpenGL version string"

On Debian, glxinfo is available as part of the mesa-utils package.

Enabling OpenGL forwarding

“Indirect GLX” must be enabled on the local computer. If it is disabled, setting it up requires root access. The way to set it up depends on the configuration of the system (the operating system and the display manager).

• On Debian 8 with kdm display manager, add +iglx after ServerArgsLocal=... in /etc/kde4/kdm/kdmrc and restart the X server.

• On Debian 9 with sddm display manager, dd +iglx after ServerArguments=...` in /etc/sddm.conf and restart the X server.