Scale individual window or individual desktop?

Certain applications are not adaptable to high DPI displays. For example in Xfig, the lines are very thin, and the icons small.

Only these applications I’d like to scale. I see two possibilities:

  • Display the application window scaled up.
  • Have one virtual desktop where the resolution is lower and all of its content is scaled up. Other virtual desktops should display windows at original size.

Can this be done with FVWM?

Elsewhere I got the suggestion to look into Wayland (not ready yet), and into compositing window managers. Also I found the composite extension for X. AFAIK FVWM does not make use of that. However, it may be possible to interface with a standalone compositing manager.

One possibility might be “xrandr”. This is an X extension allowing the change of screen resolution on-the-fly, i.e. without an X restart. So, you could, using some key combination, just temporarily switch to a lower resolution before you start xfig.
Look for some documentation; I cannot really help you with it, just wanted to give you the pointer.

In fact that was my first thought, and I may be able to hook it to switching virtual desktops. However, it’s really not my preferred solution, as it probably will cause some delay. I am still hoping that it’s somehow possible to scale the actual window content.

Decided to use VNC in the end, and wrote Vncdesk:

It’s a little tool that starts up the server and client together, to scale an app. Inside of the VNC desktop one could use another instance of FVWM, but for some applications that’s not event necessary.