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Comment by LeoNatan25 | Hacker News Reader

Sadly, outside of macOS, the support for high PPI display is dodgy at best. On Linux, it is becoming better, but still a lot more to improve. On Windows, it's a real shitshow. Windows 10, for the most part, is OK (still a lot of inconsistencies and lack of polish when scale > 100%), but application support is just terrible, be it blur, tiny scale, inconsistent elements (some small, some large) or plain crashing. Really, any vendor that makes such display is taking a risk that people will complain and a sizeable portion of the customers that purchase such a display will not understand the technical difficulties.

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On Linux, it is becoming better, but still a lot more to improve.

Even on Fedora 26, I have to manually patch and recompile Mutter to get HiDPI support on Wayland. Mutter is hardcoded [1] to use 2x scaling on displays that are 192 PPI or more. My Dell p2415q is 188.2 PPI, so you get 1x 'scaling' by default and everything is tiny. This problem has been known for a while [2].

And even though GNOME applications then generally work well, you have to start Chromium with a special flag to let it run with scaling. There are a lot of glitches throughout the system, e.g. the mouse cursor has the right size, but when you go to a window corner to resize a window, it becomes tiny. A lot of icons are blurry, because they have a low resolution and are scaled up.

macOS is basically plug & play. All applications are in full HiDPI glory. The only exception are websites that use low-resolution images. There is one catch: the (terribly expensive) Apple USB-C Digital AV Multiport Adapter only supports 4k at 30Hz. This refresh rate is very tiring and annoying. However, a USB-C -> DisplayPort ALT mode connector works great @ 60Hz.

[1] IIRC there is work in the master branch to solve this.

[2] https://bugzilla.redhat.com/show_bug.cgi?id=1258155

Chrome/Chromium is notoriously bad at adopting any technology. On Windows, it took them years to support scaling other than 1x, color Emoji was added very recently, etc. I think on Linux it is even worse. Have they finally fixed ligature support in Chromium?

With Firefox rapidly improving in performance and memory usage, less and less reasons to use Chrome.

I set Xft.dpi: 192 in ~/.Xresources (gnome-settings-daemon and others will perform the equivalent setting).

Chromium respects this (for many major versions by now) and shouldn’t need a separate flag. Are you certain the flag is necessary in your setup? Can you check what Xft.dpi is on your system? xrdb -q | grep '^Xft.dpi'

On Linux, it just depends on your desktop environment.

If you use KDE or any other Qt based one, HiDPI works perfectly at any scale, even in heterogenous environments – a landscape 4K 144ppi and a portrait 70ppi monitor right next to each other will work fine, and when moving applications they automatically rescale. On X11 and Wayland. The scale is set via the environmental variable

    QT_SCREEN_SCALE_FACTORS=DisplayPort-2=1.61;HDMI-A-0=1.08;

It’s GNOME and GTK which have almost no HiDPI support at all – they only support 96 and 192dpi (only integer scaling), and just added a feature for all other resolutions to just scale the windows down with blur. GTK2 still supported proper HiDPI, but with GTK3 they decided to abandon that and instead build apps that rely on pixels always being the same size. Considering how young GTK3 is this decision may sound a bit short-sighted, but the GNOME devs always refer to macOS as an example where this worked (while ignoring Android and Windows 10, which use fractional scaling, and ignoring the fact that with Gnome’s solution a game such as Minecraft on a 4K 144dpi screen is rendered at 6K and then half the resolution gets thrown away during the downscaling, because there is no option to avoid this)

The result is obviously completely broken.

I run Mate on two 4k monitors and it looks great, you just raise the font size in the control panel until readable.

That's not exactly true. On Linux, it's a real shit show because only KDE (Qt) supports proper fractional scaling, GTK apps don't. GTK supports 100%, 200%, and so on. You can play with xrandr, but that'll cause serious other issues (not even speaking about multi-monitor setups).

On Win10, however, all of the programs I'm using have flawless hidpi support - browsers, IntelliJ, console windows (cmder), Spotify, etc. W10 supports per-display DPI as well.

I don't know which applications are "crashing", that sounds like FUD. I know about two notable exceptions that don't have good hidpi support: Adobe tools and Hyper-V.

I'm not sure what "not exactly true" means, it's my personal experience of trying to run Windows 10 on my MBP. Many of the video tools I use regularly (for encoding, subtitle creation and editing, authoring, muxing, etc) are either broken or look bad. I understand that may not be mainstream use, but it certainly isn't esoteric either. You say browsers, but last I remember, Chrome didn't really support it. Now I am on Firefox, so it's proper, but that's not what most people use. Adobe software, as you said, is notorious at supporting scale. That's not esoteric either.

Chrome's hidpi support has been acceptable on Windows since about 2015. It's still not absolutely perfect (there are issues with 1px black bars when resizing Windows), but it's completely usable.

I've been using windows 10 with a QHD screen at 200% scaling, and it I can't complain.

Aside from a few apps that fail to scale again when I disconnect a screen from a laptop, all the apps work as expected.

I think when two monitors are connected, Windows still has issues with correctly transitioning the software from one scale to another. But that's at the system level and can be solved. The main issue is legacy software that would require complete rewrite to support scaling. A bit issue in those cases is that the community is completely unwilling to support such displays, with silly claims such as "you can't see the difference".

Rescaling between two monitors that are extending each other, even with different scales works well, its when one get disconnected and the window is forced to move to another screen that causes issues.

As to legacy software, most software works fine. Those that never cared about scaling are handled by the system easily enough. It's those rare cases where the legacy software is saying they support scaling to solve some issues with them not using the windows apis but not really doing anything to actually support scaling, such as GIMP.

Those are rare though, and usually are software with it's own rendering stack that don't use the windows apis.

I meant when moving an application window from one screen to another. I saw some issues that didn’t exist when I worked only on the MBP screen, but when I connected my 27” external display, they were suddenly issues noticeable when dragging windows.

This is simply wrong. We switched from Macs to Windows 10 because of the better monitor options available for professional color grading work. And true "Cinema" and consumer 4K resolutions are supported and supported well ONLY on Windows 10.

I respectfully completely disagree as do most professional photo/video folks I know. Color grading support on Macs is superb. There's also no commonly used resolutions supported on Windows that I know of that aren't available on Mac, so I'm not sure what you mean by the last part.

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