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Ancient X11 scaling technology

(flak.tedunangst.com)
283 points todsacerdoti | 5 comments | 24 Jun 25 18:58 UTC | HN request time: 0.002s | source
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wmf ◴[24 Jun 25 19:29 UTC] No.44370040[source]▶
Drawing a circle is kind of cheating. The hard part of scaling is drawing UI elements like raster icons or 1px hairlines to look non-blurry.
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okanat ◴[24 Jun 25 20:49 UTC] No.44370877[source]▶
And also doing it for multiple monitors with differing scales. Nobody claims X11 doesn't support different DPIs. The problems occur when you have monitors with differing pixel densities.

At the moment only Windows handles that use case perfectly, not even macOS. Wayland comes second if the optional fractional scaling is implemented by the toolkit and the compositor. I am skeptical of the Linux desktop ecosystem to do correct thing there though. Both server-side decorations and fractional scaling being optional (i.e. requires runtime opt-in from compositor and the toolkit) are missteps for a desktop protocol. Both missing features are directly attributable to GNOME and their chokehold of GTK and other core libraries.

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1. akdor1154 ◴[24 Jun 25 21:35 UTC] No.44371327[source]▶
This is exactly right.

There is no mechanism for the user to specify a per-screen text DPI in X11.

(Or maybe there secretly is, and i should wait for the author to show us?)

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2. okanat ◴[24 Jun 25 22:45 UTC] No.44371850[source]▶
Natively in X11? No. Even with Xrandr. It is no. But you can obtain the display size and then draw things differently using OpenGL but now you're reinventing the display protocol in your drawing engine (which is what GLX is after all but I digress). You need to onboard every toolkit to your protocol.
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3. somat ◴[25 Jun 25 01:00 UTC] No.44372697[source]▶
X11 has had this since day one. However the trade offs to actually employing it are... unfortunate. It leans real hard on the application to actually cross screen boundaries and very few applications were willing to put the work in. so xrandr was invented. which does more of what people want with multiple screens by treating them as parts of one large virtual screen but you loose the per screen dpi.

http://wok.oblomov.eu/tecnologia/mixed-dpi-x11/

4. uecker ◴[25 Jun 25 04:47 UTC] No.44373694[source]▶
Is this different to Wayland?
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5. okanat ◴[26 Jun 25 01:50 UTC] No.44383526{3}[source]▶
Yes. Wayland is designed to be flexible of what does the drawing and where (currently only shared memory and EGL surfaces are implemented / supported). So it needs to define monitors as abstract concepts. They are called outputs and the client can query the size directly in Wayland protocol without needing display drivers or OpenGL.

However, there is no common way of handling different custom DPIs / scaling in the core Wayland protocol. Fractional scaling is implemented optionally by the client and the server and both need to opt-in.