Add support for HiDPI screens

[Hjdskes]

Add support for HiDPI screens

[Hjdskes]

Adding a help wanted label because I do not have the hardware to test (and therefore implement) this.

[ddevault]

You can test this even without a hidpi screen - just run the parent compositor with scale=2 and live with the obnoxiously large UI for a bit. You can run wio in a hidpi window under the wayland backend like this:

 ./wio -o WL-1:-1:-1:-1:-1:2

[Hjdskes]

I think we have most bits in place for this now, but I still don't have the hardware to test. I might give Drew's suggestion a try if no-one else can test this on actual hardware.

[ericonr]

I can try it out on a 4K TV, do you think that would work?

[Hjdskes]

Only if that device is actually HiDPI. Usually, HiDPI outputs are screens with a high resolution in a relatively small physical size.

[ericonr]

Is it supposed to automatically detect that the output is such a device? If not, I could test the actual scaling itself, as @ddevault mentioned.

[Hjdskes]

It won't auto detect that, no. If you can run it with scaling that'd be awesome!

[ericonr]

https://imgur.com/a/KPbvml7 so here are the tests I made. Not sure if the issue where my prompt vanished is relevant to cage's usecase (it usually shouldn't lose focus during normal use).

There was also this weird black bar at the bottom, but I'm not entirely sure what caused it.

Is there any way I can run cage directly to try out the scaling? Or does it only work inside another compositor for now?

[ericonr]

@Hjdskes sorry for the delay! There is also some weird fringing going on with the pointer, but that doesn't depend on the scale.

Qutebrowser doesn't have the black bar at the bottom, nor the content changes when I focus or unfocus cage, so it might have been weird interaction with alacritty.

Overall I'd say it works. If you haven't implemented a way to directly tell cage the scale (specially when launching standalone), I could give it a try. Perhaps a command line option?

[Hjdskes]

Thanks @ericonr!

Is there any way I can run cage directly to try out the scaling? Or does it only work inside another compositor for now?

Currently Cage doesn't directly support this, so you'll have to test it inside another compositor for now. I can look into adding this to Cage, although ideally this would come through the implementation of an output management protocol.

I don't think Alacritty is the best test case. Not only does it seem to have a number of issues, it also doesn't have many UI elements to verify the scaling is working properly. Running a GTK3 application for example would be more indicative of a proper scaling implementation.

[ericonr]

@Hjdskes

I can look into adding this to Cage, although ideally this would come through the implementation of an output management protocol.

It's not a feature I need, so no worries! An output management protocol makes much more sense too.

I don't think Alacritty is the best test case. Not only does it seem to have a number of issues, it also doesn't have many UI elements to verify the scaling is working properly. Running a GTK3 application for example would be more indicative of a proper scaling implementation.

And damn, sorry. I had tested it out with qutebrowser (through QtWayland) as well! Which had looked fine, btw.

I can probably look into this in a few days, I will let you know. I can try both Firefox and qutebrowser for GTK and Qt examples!

[Hjdskes]

The recent scene graph work and #213 should enable everything we need here.