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Slow drawing over X11 / remote display

When you run the Understand GUI on a Linux host and view it over a forwarded X11 connection (e.g. ssh -X), drawing can feel sluggish. The GUI is optimized for drawing on a local display; sending every drawing operation across the network adds latency, and graph-heavy views make it worse.

The old -graphicssystem native flag is gone

Older SciTools notes suggest launching with understand -graphicssystem native to speed up an exported display. That option belonged to a much older Qt version and no longer exists in current Understand — passing it has no effect. Understand today runs on the Qt xcb (X11) platform plugin and exposes no in-application switch to change its rendering path for remote displays. Use the approaches below instead.

What actually helps

  • Run analysis headless; keep the GUI local. For remote/CI work, do the heavy lifting with the und command line on the remote host and open the resulting .und in a locally running GUI. Raw X11 forwarding is the slow part; avoiding it removes the bottleneck.
  • Use a remoting protocol built for it. X2Go, NX, or a VNC session composite the screen on the remote side and stream it efficiently, which is far faster than raw X11 forwarding for a graphical app. Prefer these over ssh -X for interactive use.
  • Enable compression on the forward if you must use X11: ssh -XC turns on compression, which helps on slow links (it does not eliminate per-operation latency).
  • Reduce what has to be drawn. Large graphs are the most expensive thing to render remotely. Close big graph windows you aren't using and keep individual graphs smaller — see performance on a large codebase for related guidance.