feat(experimental): window scoped extmark

[IndianBoy42]

Neovim nightly is starting to add support for window-scoped extmarks. This PR uses it to make the portal windows a little cleaner.
It is a very experimental API under active discussion.
Definitely don't need to merge, just putting this here for people to know because I think it makes a lot of sense for portal.nvim.

[chuan29812]

could be a longshot, what exactly does this accomplish? i tried adding your commit to mine, the nvim__ is already obsolete. I tried adding scoped, but dont see any different.

[IndianBoy42]

Previously/currently extmarks are scoped to a buffer, which means they are anchored to a certain buffer, line, column. If the buffer is displayed in multiple windows (including floating windows) then the extmark shows up in all of them. With window scoped extmarks it would be anchored to a window, row, column or a buffer, line, column, window making it only show up in that one window (don't remember off the top of my head how it works in nvim, haven't touched plugin stuff in a while). To me that is cleaner for portal.nvim because we can make it show up only in the active window or the floating windows

[IndianBoy42]

For reference: neovim/neovim#27361 merged the change to make a namespace window local so that the extmarks inside them only show up in that window. The updated version of this PR should create namespaces for every window that the portal labels should show up in and add extmarks to that oh that is what I did, it just needs the updated name

[chuan29812]

@IndianBoy42 thanks for the reply. TIL, im guessing the h and k extmark just wouldnt be showing in the right window if its scoped to the buffer? btw, i tried only appending the scoped: true in the window.lua file, nothing changed. Probably requires more work. haha