HiDPI on XFCE4 (Xubuntu Xenial)

[^rooker]

Running Xubuntu 20.04 with XFCE 4.14 on a 2k display.

Here's what and how I've configured to make it look and feel fine:

I'm pretty sure I've not configured my setup completely right for the first time.
So I must admit I'm surprised that I don't want that 2k display on my main machine (for now), because UI-sizing (especially font size) is quite a bumpy ride. At least on XFCE. Haven't tried other Window Managers with that screen yet.
I'm really very fond of XFCE4! A loving user since 2006.

That's why I want this to work.
And I'm hoping to be able to contribute back upstream, so new installs won't have to manually-tweak before they can "just happily use" their 2k/4k displays.

btw: I'm actually a bit skeptic when it comes to >HD for moving image.
I usually recommend to almost all end-users that FullHD is perfectly fine.
Especially for a TV and computer display.
Unless working with graphics or cinema film.


0) Settings > Display > General
* Resolution to 2560x1440 (16:9)
* Scale: 1x (!)

When using "scale<1.0" for resizing to match your UI for 2k high-dpi display, things get (at least on my system) quite blurry. Looks like in the early days of LCD displays, when we were used to setting a lower resolution to "zoom" the image on CRTs for our grand/parents. Not so clean IMO.

So I leave the scale at 1.0.

1) Settings > Appearance > Fonts: Custom DPI setting

I've set my font DPI value to "144".

2) Settings > Window Manager > Window decoration font size

Adjust the font-size and style to use for your window titles.

3) Firefox default zoom.
I've set mine to 90%.

4) (optional) Firefox scaling

In "about:config", edit the following value:

layout.css.devPixelsPerPx = 1.8

I've used this before, when I had set the custom font DPI to 72, and resized everything else. Didn't work too well. Especially messed up font-size (suuuuper tiny) in all Qt applications. Anyways: Now you know a way to zoom Firefox's complete UI if you like. Not just the websites (that's "Zoom").