On my dell XPS 13, 9360 model, there is a HiDPI display, the resolution is 3200x1800 which is fantastic but it has resulted in some GTK applications (and multiple Qt applications) not having the correct scaling factor applied. I have already fixed this for Qt applications but now I would like to fix it for GTK-based applications like the GIMP and other programs.
Here is an example of what I mean:
The whole user interface of the GIMP is at 1x (unscaled) while the file manager is at 1.5x or 2x; it's the perfect scaled size.
How do I fix this? With a tweak tool or use gconf editor or something else?
I have the same machine.
I think you're likely out of luck. HiDPI support is far from perfect in any distro. I've found that applications that use the GTK3 UI framework look good on HiDPI screens but applications using the older (but more prevalent) GTK2 framework look poor. I don't think there's an easy fix for it other than getting the developers to update their apps to a more modern framework.