Comment # 25 on bug 1123424 from Stefan Hundhammer

(In reply to Fabian Vogt from comment #22)
> > When I use "ssh -X" to that machine to try to start qdirstat via remote X,
> > it still appears on that Wayland display (i.e. in the VM, not on the remote
> > X server),
> 
> Do you ssh -X from inside the VM or from the outside?

I did that from the outside.

I tried again, and the result was a bit surprising:

  [shundhammer @ morgul] ~ % ssh -X tux@g1 
  tux@g1:~> echo $DISPLAY
  localhost:10.0
  tux@g1:~> qdirstat .

  Logging to /tmp/qdirstat-tux/qdirstat.log
  libGL error: failed to load driver: swrast

-> QDirStat runs on the Wayland display (??)


  [shundhammer @ morgul] % ssh -X root@g1
  g1:~ # echo $DISPLAY
  localhost:10.0
  g1:~ # qdirstat .

  Logging to /tmp/qdirstat-root/qdirstat.log
  libGL error: failed to load driver: swrast


-> QDirStat runs on the remote X server as expected
   (with unscaled fonts etc. and perfectly normal rendering)


> Desktop settings should not have any effect on scaling at all - unless some
> third-party plugin uses the private API.

I don't know what exactly that GNOME "Tweak" application does, but it does
affect Qt programs. After using it I find that "Xft.dpi" X resource in the X
server changed; maybe that's all that it does.

  tux@g1:~> xrdb -query | grep Xft.dpi
  Xft.dpi:    120.9599609375
  tux@g1:~> echo Xft.dpi: 120 | xrdb -nocpp -merge
  tux@g1:~> xrdb -query | grep Xft.dpi
  Xft.dpi:    120
  tux@g1:~> gnome-tweaks 
            (change the font scaling in that program's "Fonts" page)

  tux@g1:~> xrdb -query | grep Xft.dpi
  Xft.dpi:    120.9599609375