Rudimentary Touch Bar support

[greg]

Adds a basic Safari-style control for switching between open tabs, showing the filename of the most recently selected window within that tab as the title (which the nvim provided tab bar behaviour).

This addition required some modifications to NeoVimServer and NeoVimView+Api which do not appear to have broken anything, but I am not familiar enough with the codebase to be completely sure.

I hope this is useful for some people; if it is, I'll work on adding more Touch Bar features.

Testing note: if you don't have a Touch Bar, Xcode has a Touch Bar simulator (Window > Show Touch Bar, or ⌘⇧5).

[qvacua]

Thank you for the PR. I'll review it and come back to you. 😀

[qvacua]

I finally came to try it (haven't had time to look at the code though...). It seems that sometimes the titles of tabs are not displayed. I also tried it on an MBP with TB and it also happens there. Could you look at it?

[greg]

I couldn't reproduce this on macOS 10.13, but it looks like I was setting the segmented control titles incorrectly — I've pushed a fix that will hopefully correct this on earlier versions.

(If you are also on 10.13, then I'm a little lost as to why this issue would occur 😝)

[qvacua]

Thanks. Yes, I'm on 10.12... I'll re-check and give you feedback. :)

[qvacua]

This seems to be the problematic check (on 10.12.x at least): If I remove it

guard ...
tabsCache = ...
tabsControl.reloadData()
tabsControl.selectedIndex = selectedTabIndex()
return // do we need `reloadItems(at:)` even we reload completely?

the touch bar is updated correctly.

I think that the count check is too coarse and it's not expensive just to reload here. (We could iterate through all the tabs and windows and update the touch bar items individually, but that's probably an overkill.) The transition of the touch bar when the number of tabs changes is not smooth, but I think that that's a minor detail we can improve later. 😀

[qvacua]

I think that it'd be better to update tabsCache at appropriate places in NeoVimView+UiBridge since it's not necessarily touch bar specific (although it's currently used only by the touch bar logic)