Changing font size in all OS windows at once

[stinovlas]

Hi! I recently migrated to kitty from alacritty. I have to say kitty is amazing and I'm still going through a heap of useful features it provides out of the box. One thing I've been struggling with is changing font size in all OS windows at once. This is very useful feature for me, because I carry my laptop around and attach it to differently sized monitors with different resolutions.

What is the problem

The documentation says that map kitty_mod+plus change_font_size all +2.0 should affect all OS windows, but curiously, it didn't work for me. I use i3 and I had the following in my i3 config:

bindsym $mod+Shift+Return exec kitty

It turned out, when you execute kitty this way, it spawns several kitty instances. And change_font_size all only affects all the windows in single kitty instance.

My solution

First I wanted to utilize remote control, but then I stumbled into useful command line option --single-instance. If you use it, kitty will attach new windows to an existing instance instead of creating a new one. So I changed my i3 config to this and everything works like a charm:

bindsym $mod+Shift+Return exec kitty --single-instance

Note: there's also --instance-group CLI option, if you want to group windows into several separate instances. I don't currently have a use for that.

Note: I understand this is a weird Q&A, because I already found the answer, but I spent some time with it and I thought someone else might find it useful. Furthermore, there's still an open question of affecting the font size over all running kitty instances (remote control?) if anyone has use for that.

[kovidgoyal]

Just for completeness, you can also update the value in your kitty.conf file and have all kitty processes reload their config wit something like killall -USR1 kitty

[stinovlas]

Thank you, this is useful! I can imagine having a small config file included in the main kitty.conf which I would edit with in-place sed and reload the config as you suggested. Not necessary for the simultaneous font size change, but maybe I'll find another user for it.