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Ancient X11 scaling technology

(flak.tedunangst.com)
283 points todsacerdoti | 2 comments | 24 Jun 25 18:58 UTC | HN request time: 0.456s | source
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jchw ◴[24 Jun 25 21:42 UTC] No.44371382[source]▶
Sigh. And now that it's been long enough, everyone will conveniently forget all of the reasons why this wound up being insufficient, and think that all of the desktop environment and toolkit developers are simply stupid. (Importantly, applications actually did do this by default at one point. I remember a wonky-looking nvidia-xsettings because of this.)

The thing X11 really is missing (at least most importantly) is DPI virtualization. UI scaling isn't a feature most display servers implement because most display servers don't implement the actual UI bits. The lack of DPI virtualization is a problem though, because it leaves windows on their own to figure out how to logically scale input and output coordinates. Worse, they have to do it per monitor, and can't do anything about the fact that part of the window will look wrong if it overlaps two displays with different scaling. If anything doesn't do this or does it slightly differently, it will look wrong, and the user has little recourse beyond searching for environment variables or X properties that might make it work.

Explaining all of that is harder than saying that X11 has poor display scaling support. Saying it "doesn't support UI/display scaling" is kind of a misnomer though; that's not exactly the problem.

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1. account42 ◴[25 Jun 25 16:08 UTC] No.44378873[source]▶
Applications (or rather UI toolkits) need to handle scaling no matter what if you want a crisp result without giant intermediate renders. Figuring out the scale is the easy part as the article shows.

> Worse, they have to do it per monitor, and can't do anything about the fact that part of the window will look wrong if it overlaps two displays with different scaling.

That is not a real issue. Certainly not anything worth breaking backwards compatibility and even if you care about cosmetic issues like this you can fix them with extensions.

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2. jchw ◴[25 Jun 25 19:23 UTC] No.44380973[source]▶
That's fine. It doesn't need to be absolutely perfect, it just needs to be good enough. What isn't good enough is if you can't even use legacy apps because they're too small. What is good enough is if DPI aware apps can have crisp rendering and DPI-unaware apps can render at the correct size on screen but blurry. Totally fine, it's exactly what Windows and macOS (and not X11) do.

You can fix this with extensions... Kind of, anyway. It's really not that trivial. Like if you do DPI virtualization, you need it to take effect across literally everything. Like for example, some applications in X11 will read xrandr information for window placement. To properly handle DPI-unaware applications, you need to be able to present virtualized coordinates to some applications. This is actually one of the easier problems to solve, it goes downhill from there.