> dual monitor setups that aren't the same.

Absolutely categorically false: I daily-drove such a config on openSUSE for 4 years, 9-5 Mon-Fri.

One portrait, one landscape: fine. 2 portrait flanking one landscape: fine. Laptop + 2 external displays, 1 big in portrait, 1 small in landscape: fine. 2 screens, vertically stacked: fine. 2 side-by-side, one big one small: fine.

Everything works exactly as expected. Panels stay put. Some apps can't remember their positions but they can't on any WM or desktop.

Very dissimilar resolutions gets tricky but that's down to Xinerama not Xfce. It's true on all X11 desktops.

Xfce can do fractional scaling on a per-display basis to get on-screen features the same size, but it results in some displays getting slightly blurry. Tolerable for short-term use but not all day every day, for me.

But Xfce is 100% usable in heterogenous multihead and indeed handles this as well or better than almost any other mainstream X11-based desktop.

How high? What kind of problems?

I very recently upgraded from a dual fullhd to a dual 4k setup and I was genuinely surprised how little problems I had setting everything up to the high DPI displays. I am genuinely interested in hearing what pitfalls might still await me.

Most HighDPI issues on X based DEs is from lack of fractional scaling, which means the scaling needs to happen in the applications instead (with separate configs for each UI toolkit), leading to lots of weird issues with inconsistently scaled UI elements on monitors sized such that integer scaling produces an inappropriate scale.

It doesn't affect all monitors, but some DPIs really don't play well with X. The fractional scaling you get on Wayland leads to some element of blur instead, but that's a far lesser evil, the jank is a bigger issue IMO.

I've been running 2× 4k 27" monitors for about a year on Xfce. I set it to 144 ppi and nothing feels weird to me, though I run a custom theme.

Thanks for sharing the ppi hint, this helped me out a lot with not having to zoom every app on my 4k monitor!

This is why I switched from XFCE to KDE. I still use XFCE for server desktops (if they have one) as it gets out of your way and lets you do easy things easily. I did spend a while recently trying to figure out how to get a Gnome desktop to autostart a terminal and ended up mucking around with installing desktop extensions just trying to specify a startup command.

I've been using XFCE for several years on 4k screens and I agree that it's not great out of the box.

Once you've set it up it works pretty well though.

Now if only I could remember what I did to get it working nicely...(luckily I've had the same installation of XFCE on my machine for the past 5 years so haven't had to fiddle with that in a while)

I just set dpi to 128 or 192. The out-the-box 96 could do with changing.

You can do some xrandr magic to make it better and set a virtual rendering target that keeps things consistent across screens. It's a bit of a pain to work out though.

Thing is: my default IceWM works better on the same monitor here than XFCE does. Something seems to not be considered by the current XFCE code.

Haven't thought about IceWM in ages, that's good to know it works out of the box well. I'll have to check it out!

Yeah, everything on my notebook is quite small.

But now I have so much screen real estate, I'm almost considering using a tiling window manager.

Make sure you have a HiDPI theme selected and that you set a custom DPI that matches your screen in Settings->Appearance->Fonts.

Yeah, I noticed this recently with my ultra-widescreen monitor. That was indeed strange; normally XFCE works super-well.