I run Gnome, which has pretty good support for my HiDPI screen. However, when I run QT apps I can't seem to find a way to scale the fonts. Is there a way to do this without installing a full version of KDE?
You can try this recipe from the archwiki
Qt5 applications can often be run at higher dpi by setting the QT_DEVICE_PIXEL_RATIO environment variable. Note that the variable has to be set to a whole integer, so setting it to 1.5 will not work.
This can for instance be enabled by creating a file
And set the executable bit on it.
QT_DEVICE_PIXEL_RATIO is deprecated since 5.4; instead, use
QT_SCALE_FACTOR. I use it, setting it to 1.5, with good results (e.g., VirtualBox 5.1)
QT automatically scales the font based on the screen's DPI:
The traditional approach to supporting high DPI has been one where Qt scaled fonts automatically [...]
I had the problem that my screen has 166 dpi, but the font sizes chosen by Qt were much too large. Luckily, there is a way to tell Qt to assume a smaller value by setting
QT_FONT_DPI. For me, 128 is nice.
(I'm using cinnamon as desktop environment, and it pushes the configured font sizes for Gtk 1:1 to Qt, which is what brings this issue)