The bad news: There's no unified HiDPI solution on Linux that works well end-to-end.

The good news: You don't really need one.

Bumping the font configuration fixes 80% of the scenarios, and the rest I tweak on a case-by-case basis. The good standards-conforming apps (e.g. modern terminals, browsers, etc) automatically multiply the font sizes by your screen DPI. Most desktop managers have a scale sliders for the GUI size, if you're into that. Some stragglers include Steam which recently added support for a 2x size multiplier (it's something, but not the best).

You kinda get exposed to how the sausage is made, but the sausage still tastes great.

Linux desktop is better than it ever was, but the road to perfection is long and eternal.

my system76 handles 4k perfectly

system76 actually ships a custom daemon that makes mixed LowDPI/HiDPI setups easier to manage, and I hope other distros will follow suit:

https://elementaryos.stackexchange.com/a/14234

HiDPI on Linux is pretty much non existent. I am telling from experience. I have booth a decent 4K external monitor and a HiDPI IPS internal display. The only setup which is ok in the sense of least horrible is Gnome mutter Wayland with experimental per monitor fractional scaling enabled. And this one is only ok if you can restrict yourself to the few ported pure GTK3 Gnome apps. Which means not that much. No Firefox. No Chrome. No Thunderbird.

And the speed of fixing HiDPI on Linux has actually slowed down.

Frnakly, and I am a hard core Linux OSS fan - come back in two years and check again.

The Linux desktop IS dead.

Huh? I've been running a 2x/192dpi Linux/X11 laptop for a couple of years, and the experience has been near perfect. Hands down better than on Windows. Some DEs even detect the panel DPI and configure toolkit scaling automatically. Firefox and Chrome have been two of the most well-behaved apps, especially since they switched to GTK3, but it's not just GTK3 that is well-behaved, Qt5 is as well. Since most apps I use are Qt5 and some are GTK3, they all get crisp HiDPI rendering automatically from the toolkit.

So I'm not sure what you mean by "HiDPI on Linux is pretty much non existent." Maybe it gets worse if you need fractional scaling or displays with different scaling ratios, but these seem to things all platforms are struggling with. Microsoft only made built-in apps like File Explorer per-monitor-DPI aware in Windows 10 1703 (released a year ago), and macOS doesn't attempt fractional scaling (eg. 1.5x, 2.5x, etc.) at all.

So, what exactly is it that you expect as "HiDPI" support which is missing? As far as I can recall, it has been possible to configure the actual physical size/DPI for a monitor for many, many years. Any properly functioning X application should then be able to draw things a correct size on the screen, e.g. fonts sized in points or images and figures scaled to actual widths. I think this infrastructure may even pre-date the switch from XFree86 to Xorg. Is your complaint that there are still some applications which ignore this monitor DPI metadata or which do other pixel-based techniques?

Like the previous poster, I stick to 1920x1080 on my 14-inch class Thinkpad. In my office I have dual 28-inch 4K monitors. These have identical dot pitch to my Thinkpad, so each monitor is like having a 2x2 array of my Thinkpad screens. When I made sure the monitors were set with the correct DPI, everything worked exactly as I would expect. Whatever rendered as one pixel on my laptop would also be one pixel on my workstation, and I just had 8 times more real estate on my dual monitor desktop. But, I sit further from the monitors than I do my laptop screen while also using them for much longer stretches of time. So, I adjusted the workstation to pretend it had higher DPI so that things would render a little bigger.

It's been a few years, but I think I may have had to separately adjust Firefox because it has some of its own weird assumptions about fonts and DPI that I assume come from their renderer straddling several different platforms. I also had to adjust emacs and xterm to change from my decades old fixed font preferences to start using scalable fonts.

Mix HiDPI screens and non HiDPI ones, lots of very real corner cases that you hit daily make the experience terrible in ways that can only be "fixed" through terrible hacks and tweaks, if at all.

OK, so I guess the problem comes from trying to fuse everything into one screen? In the old days, we would run X with separate screen numbers to get multiple outputs via multiple graphics cards. You could slide your mouse between screens, but you couldn't drag a window across or have a window spanning the two screens. Each window remained confined to one screen, and only a few apps knew how to open windows on more than one screen from the same app instance. (A few, like emacs, even understand opening windows on multiple displays!)

Out of curiosity, what is a non-broken behavior supposed to be if the screens are combined? Do people expect the low-dpi screen to be a blurry version of whatever would appear on the high-dpi screen, or do they expect it to act like a magnifier, perhaps with pan/zoom controls?

> In the old days, we would run X with separate screen numbers to get multiple outputs via multiple graphics cards

Those days are gone. No matter how hard you try - either you are simply not runing on current hardware, have very modest expectations or close your eyes to realize that the Linux desktop in this regard is at least two years behind, minimum!

I am not arguing, I am genuinely wondering what you guys want. I have read multiple assertions that Linux is broken but no clear explanation of what it should be doing differently.

For reference, I have been using Linux continuously on all sorts of hardware since 1994. What I lack is any practical experience using modern Windows or Mac OS, so I have no idea what implicit expectations you may be bringing from those. The last time I ran Windows directly on hardware was before Windows 95 was released, and similarly my only real Mac experience was on monochrome classic Macs before OS X existed.

Over the years, I have used just about every sort of display hardware with Linux, ranging from serial terminals, Hercules monochrome graphics, 800x600 through 1600x1200 CRTs, the first wave of DVI-based LCDs, various HDTVs, the first DLP projectors, and my current dual 4K monitors. I was also involved in the early testing and deployment of 2D and 3D accelerators on Linux, as well as things like clusters driving arrays of projectors. We even had one of those IBM "Big Bertha" displays in our lab at one point, which was one of the first 300 DPI LCD monitors available. Just about the only thing I haven't used with Linux is head-mounted displays nor stereo glasses. My last involvement with VR was 20 years ago when SGI Onyx-based CAVE systems were prevalent in academia, combining head-tracking, active shutters, and multiple wall projectors.

But, to be honest, I have no use case to combine different DPI monitors into a single graphical screen or desktop. If I connect a laptop to a projector or display panel for presentations, I tend to just want to duplicate the presentation view on the internal screen. Otherwise, I use the laptop to be mobile and I use workstations with their dedicated displays.

Try KDE on Wayland. Full support for HiDPI, full support for multiple monitors of different DPI even.

I did. I recently switched from KDE after more than 15! years to Gnome because KDE on Waykand is broken beyond usability. It comes for a reason that even Neon, which I used back then, doesn't come with Wayland out of the box.

And frankly, X is a dead end.

> broken beyond usability

Were you using Nvidia? On AMD and Intel it’s been working amazing for me so far, never had any issue. Nvidia is known for disobeying the standards.

It's Intel and its not the pure hraphics but the ecosystem. Wanted to enter diacretics into Emacs? The quick search bar poped up instead an accent egu in Emacs (compose key). It's that sort of things, not directly bad display. The end result was nevertheless unusable though.

HiDPI on Linux is only broken if you need fractional scaling, or different per-monitor scaling factors. If you stick to screens that work well at 200% (e.g. 4K on 24"), then current desktops will work just fine in my experience.

That sounds like a draconian restriction if you are coming from Windows 10, but OP is switching from macOS. Macs have traditionally used either 100% or 200% as well (except for the latest-gen MBP).

Linux desktop is doing fine. But I prefer to avoid GTK when possible. It's years behind Qt. Some thing like Firefox are necessary though, but it's a pity it's stuck with GTK.

linux desktop is isn’t dead.

The biggest problem in linux is not directly HiDPI. HiDPI works (mostly).

However if you can't use wayland you will have a problem when you need the following:

Multiple monitors with different screen resultions. Lets say your laptop has 4k and you use two external monitors with 1080p than it gets tricky with older wayland or x.org. However on later stable/edge channels most things are probably better than when I tested this and I even have a colleague which has a 13" xps with ubuntu which works pretty will with its docking station.

If you have a good GPU you can use the xrandr commandline tool to set up display scaling, so your secondary low-DPI screen is rendered at high DPI and scaled down. Then you only need one DPI setting for your DE.

Well, it‘s good that it „could“ work, however i expect it to work without searching the Internet for xrandr configs. (And as said newer Weston/Wayland work way better)

I agree; I post the fact that its possible more as a condemnation of the UI for not getting it right.

2560x1440 doesn't even require HiDPI support really. Just increasing the font sizes is enough. The Ubuntu Unity desktop has abstracted away that in a single slider for a long time. Apparently the next GNOME version is going to go all the way and do non-integer scaling of controls as well but in my experience that's just a small benefit, just tweaking up the font sizes is more than enough.

Surprisingly, both engineers on the 2560x1440 are happy! They run Ubuntu with a second screen at their desks (27” 2560x1440 external monitors). I’m actually the one that’s unhappy because their font size is too small for me to see when pairing ;)

BTW I think 2560x1440 may not be high enough to technically be considered HiDPI?

As someone with a 2560x1440 (27”) display at work and a 5120x2880 (27”) display at home, the former is very much not HiDPI, not even close :)

DPI is Dots per inch. It's a density. As a matter of fact, 2560×1440 on a 14" notebook display is nearly identical to 5120×2880 on a 27" display.

I'm talking about 2560x1440 on 27", as is GP, and comparing that resolution at 27" to the pixel doubled resolution at 27"?

108 PPI for the former is not HiDPI, which is my point.

I'm quite aware of pixel density, but thanks for the Wikipedia definition.

I wish everything just used wayland and scaled correctly I am sick of having to launch chrome with an environment variable so it can run on one screen and having another instance for another. Also silly things like file dialogs not fitting. It's annoying when you look and the issues are all from years ago and still not fixed.

It's actually quite OK, with just some minor annoyances. Three scenarios for my use case:

1. Use the laptop screen only. This is easy. Just change the DPI value in my ~/.Xprofile and everything is solved.

2. Use external monitors only. Just use the default DPI value.

3. Use laptop screen in combination with external monitors. This doesn't occur hat often. But when I have to do this, there are also some ways to make it work. You can refer to https://wiki.archlinux.org/index.php/HiDPI for some reference.

- The first way is to increase the DPI in ~/.Xprofile and actually scale up the external monitor instead. I don't like this method since the external monitor just looks blurry for some reason.

- Or you can keep the DPI and downscale your internal monitor.

- Or, and this is what I do currently, use apps that support manually setting DPI in their settings, e.g. Firefox and Thunderbird, on the laptop display. You can also manually change font sizes of apps that you're going to use on the laptop display. This is a bit inconvenient but the display result will look totally natural.

I have no problems on KDE for home use, I think the problems are mixing multiple screens with different pixel densities.

Best i understand, the problem child is Gnome. The devs involved there basically ignore xorg provided DPI information, resulting in all kinds of problems.

Works great with Mate.

Gnome has always worked pretty well with High DPI. But yes Linux display managers are generally pretty bad, as I learned with my 1440p 13 inch laptop as recently as 2015.

I have a Thinkpad P71 and I run NixOS on it. Works great with a 5k monitor, and DPI is perfect.

Most apps are written in GTK or Qt, which do scaling well.

The main issue is that scaling can't really be done on a per-display basis.