Comment by encom | Hacker News Reader

Comment by encom | Hacker News Reader

I've been running a mixed DPI setup for a long time now, with a 4K display center, and a vertical 1080p display on either side (so 3 displays total).

My conclusion from running this and similar mixed DPI setups over many years is that mixed DPI is extremely poorly tested, if at all, by all vendors. KDE Plasma on Wayland finally pretty much gets it right 98% of the time. X11 wasn't a great experience, regardless of what's technically possible.

Windows has so many annoying issues. Apps are often blurry on the low DPI displays. The mouse cursor has no concept of screen DPI, and treats the entire working area as having the same DPI, so you have to hit the "exits" of the high DPI display just right to land on the low DPI ones. Positioning a window across different displays only scales it correctly on one. There's probably more, but I've been 100% Windows free for a couple of years now.

I wonder how OS X handles it. I don't like that OS, but it sounds like the kind of thing Apple would care about getting right.

> X11 wasn't a great experience, regardless of what's technically possible.

I use FreeBSD as my daily driver and as well I use four screens, 2x4k and 2x1080p.

There are glitches and it's no near perfect but I would highly praise Xorg/X11. I've had no issues in a long time; maybe it's your distro.

macOS (and iOS/iPadOS) is one of the least "technically correct" when it comes to DPI (it uses only the render-at-integer-multiple-and-scale approach) but it does support per display settings pretty well. Everything is also built with the assumptions displays will be high DPI so low DPI screens have crap fonts and whatnot. For windows across multiple displays I'd have to check to see the behavior of but I wouldn't hold up hope it's particularly great. Like you say, Microsoft Windows has one of the most ideal technical implementations (fractional per monitor DPI + it at least attempts to display the window across monitors in a way doesn't bitmap scale) and reached this state many years ago but it means nothing if all the apps aren't also updated to support it (much like this article).

The cursor thing isn't really to do with DPI, it's a general thing with mixed reported display sizes regardless if they have the same DPI. I wish more systems had the option to cross borders at the relative position between monitors rather than the absolute but neither is necessarily more correct and I'm sure many prefer the absolute method.

> Positioning a window across different displays only scales it correctly on one.

Apart from automatic OS-level scaling applied as a post-processing step, which is almost guaranteed to look bad, this one is basically impossible to fix (from a technical standpoint). If you need to move "smoothly" between monitors, get identical monitors.

macOS doesn't handle it at all, a window is never visible on multiple screens at the same time.

Low DPI screens are near unusable anyway on macOS without subpixel rendering

Ha, so that's just one issue instead of dozens!

Take that, Apple haters.

> macOS doesn't handle it at all, a window is never visible on multiple screens at the same time.

It absolutely is during dragging. macOS is perfectly capable of drawing a window on two screens at the same time, but it doesn't let a window cross two screens while resting which I think is a really good user experience choice.

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