Buffer attach delta is mishandled

[kennylevinsen]

Sway largely ignores the buffer attach point, and uses it to offset a surface away from its view origin, which is not correct behavior. This behavior can be observed by running the wleird resizor client.

Sway should instead use the buffer attach point delta to move floating windows, and ignore the buffer attach point otherwise.

It should be noted that the wlroots API here seems a bit awkward, as wlroots adds the deltas to x/y coordinates on the surface. To get the delta, which is the only interesting value, we must reset these coordinates to 0 on commit.

[emersion]

Yeah, the wlroots API is weird. It was supposed to simplify compositors, allowing them to just add the accumulated x/y attach coords to their final coordinates. This doesn't work well in practice.

I'd really want to avoid having the last attach x/y delta stored in wlr_surface though, since it's really a per-commit thing. We should probably expose it in the surface commit event struct.

[kennylevinsen]

We should probably expose it in the surface commit event struct.

Agreed. I was thinking of maybe a dedicated surface move event, but adding to commit events works too.

I did get things working with the current API, but it's not very nice at all.