Qubes-Community-Content/docs/customization/dpi-scaling.md
2018-04-16 16:27:29 +03:00

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DPI scaling

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 vertical resolution is greater than 1200px) but for a variety of reasons one may have to set a custom dpi scaling value.

Dom0

The simplest way to set dpi scaling in dom0 is to use the desktop environment's custom dpi feature:

  • Xfce: Qubes Menu → System Tools → Appearance → Fonts tab: Custom DPI setting: xxx
  • KDE: Qubes Menu → System Settings → Font → Force font dpi: xxx

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.

VMs

The procedure for setting DPI scaling depends on the presence of the /usr/libexec/gsd-xsettings daemon, usually provided by the gnome-settings-daemon package:

  • without /usr/libexec/gsd-xsettings running, applications honor the Xft.dpi X resource, which we can use for scaling.
  • with /usr/libexec/gsd-xsettings running, applications are prevented from using the Xft.dpi resource so gnome specific commands have to used.

Notes:

  • the official fedora-xx template has gnome-settings-daemon installed by default while the fedora-xx-minimal template doesn't.
  • DPI scaling with xterm (or any glib apps) requires the use of a xft font:
    • for xterm, ctrl - right click in the terminal's windows and select 'TrueType Fonts' (make sure you have such fonts installed).
    • or more generally, set the faceName Xresource, eg. XTerm*faceName: DejaVu Sans Mono:size=14:antialias=true. You may do so temporarily with the xrdb -merge command, or permanently in a Xresources file (see section below).

VMs without gsd-xsettings

Get the current value of Xft.dpi:

xrdb -query | grep Xft.dpi

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):

echo Xft.dpi: 144 | xrdb -merge

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 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.

VMs with gsd-xsettings

Use the gsettings command (replace 2 and 0.75 to suit your needs ; the first value must be an integer though):

gsettings set org.gnome.desktop.interface scaling-factor 2
gsettings set org.gnome.desktop.interface text-scaling-factor 0.75

Resources

Contributors: @taradiddles