This is something we should do.

The Ctrl+MouseWheel is actually not a Mumble feature. It's not even intended to work like that. It's just a feature of the underlying view we use for rendering the log.

I guess we need separate font settings for Log, Input and Channel Tree, but still allow to set them all at once.

This feature request is still open.
That commit is from 2015 and we have 2017 and still not font setting in configuration->Settings->user interface (Mumble 1.2.19 on Windows).
Chat is practically unsuable on modern high-DPI displays if the user doesn't happen to know CTRL+mouse wheel and actually HAS a mouse-wheel (touchpad).

HiDPI is supported in Mumble 1.3.0 snapshots. Please use those if you need HiDPI support. (We should hit beta on those soon.)

This PR serves a different purpose: It doesn't scale everything, it only scales text in the log. Its purpose is to make the ability to set the text size for the log view more discoverable.

No such release on Github. Nothing on mumble.com .
Where to get that?
Hopefully it doesn't "scale" the text but render it with the correct DPI settings, so 10pt=3.5mm.
I would be forced to use the default font size but at least that font size (in pt) would result in the height in pixels that was originally intended.

Mumble.com is not affiliated with the Mumble project. Our website is https://www.mumble.info.
It's not on the GitHub releases page since it's a pre-release snapshot.

I can't speak to the specifics of the technical implementation, because that is handled by Qt. But feel free to file issues here if you find any inconsistencies. Thanks!

This would be nice not only for the chat window font size but also for the menu bar font size or all/most fonts in the client.

There's a (WIP) PR for all of it, but we didn't find the time yet to actually process it. See #1872