Qubes OS passes on dom0's screen resolution to VMs (this can be seen in the output of `xrandr`) but doesn't pass on dom0's dpi value. Recent distributions have automatic scaling depending on the screen's resolution (eg. in fedora if the screen resolution is at least 192dpi and the screen height is greater than 1200 pixels) but for a variety of reasons one may have to set a custom dpi scaling value.
Replace `xxx` with a number that fits your setup and is a multiple of 6, as numbers that aren't sometimes result in annoying rounding errors that cause adjacent bitmap font sizes to not increment and decrement linearly.
Qubes applications (e.g. Qubes Create VM, etc.) don't scale automatically, to solve this issue it is possible to set the `QT_SCALE_FACTOR` variables as described
[here](https://doc.qt.io/qt-6/highdpi.html#qt-scale-factor3). To test these
values first, open a terminal and type:
~~~
QT_SCALE_FACTOR=1.8 qubes-global-settings
~~~
You can try change the values for `QT_SCALE_FACTOR` to your
liking.
Once you confirmed that this is working, you can make these settings permanent
by creating a file `/etc/profile.d/dpi_QT.sh` (in dom0) with
- if the daemon is stopped/not installed, applications honor the `Xft.dpi` [X resource](https://en.wikipedia.org/wiki/X_resources) which we can then use for scaling.
- if the daemon is running (`/usr/libexec/gsd-xsettings` process in Fedora), applications are prevented from using the `Xft.dpi` resource and `dconf` values have to set.
Test with a different dpi value: in a terminal issue the following command and then start an application to check that the menus/fonts' size is increased/decreased; replace '144' with the value set in dom0 (it's possible to set a different value in VMs though):
Once you found a value that fits your setup you'll likely want to permanently set the `Xft.dpi` resource. You can do so on a per-template (system-wide) or per-VM basis:
- add (or modify) `Xft.dpi: xxx` in the TemplateVM's Xresource file (`/etc/X11/Xresources` or `/etc/X11/Xresources/x11-common` for whonix-ws-template).
- or, add `Xft.dpi: xxx` to `$HOME/.Xresources` in each AppVM.
To store the dconf values system-wide - eg. when customizing templateVMs - copy the following text into `/etc/dconf/db/local.d/dpi` (replace `2` and `0.75` with your values):
Note: the `scaling-factor` and `text-scaling-factor` values might already be set in an AppVM's user profile, in which case they'll override the system-wide ones. To use system-wide values, reset the user values like so in the AppVM(s):
For more information on setting system-wide dconf values see [this page](https://help.gnome.org/admin/system-admin-guide/stable/dconf-custom-defaults.html.en).
