Fix anchoring in kwin and smithay

[itshog]

Should resolve #165; should also fix #170. Instead of setting all anchors for centering (or, for instance, setting both left and right anchor to achieve horizontal centering), we now only set the needed anchor.

See this fuzzel commit for more information.

[chriselrod]

This works for me on niri.

[philj56]

Hey, sorry for the slow response on this and thanks for the PR! Unfortunately this issue isn't quite so simple.

The reason opposing anchors were set to centre the window, rather than neither, was because this is required to get a full-width / height window on a compositor that:

• Supports fractional scaling
• Does not support the wp-fractional-scale-v1 protocol.
  In this scenario, it's impossible (I think) for the window to determine how big it needs to be, at least in the way tofi works.

With this patch set, setting --width=0 --anchor=center on sway gives me:

zwlr_layer_surface_v1#20: error 1: width 0 requested without setting left and right anchors

and no visible window.

Back when I was last updating tofi, wp-fractional-scale-v1 was not widely implemented, so I couldn't rely on it.
Nowadays however, it seems almost all compositors support it, so we can probably get rid of the legacy --width=0 behaviour. I think the correct thing to do is:

• Make a release (soon!), with warnings that --width=0 and --height=0 are deprecated, and 100% is preferred.
• In the release after that, remove --width=0 support and merge this.

[itshog]

I think the correct thing to do is:

* Make a release (soon!), with warnings that `--width=0` and `--height=0` are deprecated, and `100%` is preferred.

* In the release after that, remove `--width=0` support and merge this.

This seems reasonable to me, thanks for looking into this. Any way we can help?

[Fireye04]

Setting up tofi on niri and would love to see this PR merged soon, is there any timeframe for when it might happen? I'm happy to build tofi from source with the patch till then, just wondering when I can expect the fix to be released.