Re: OSX FSEvents file watching support

[Mattias Engdegård]

17 juli 2019 kl. 06.18 skrev Muir Manders <address@hidden>:
> 
> I am interested in adding support in Emacs for Mac OS "FSEvents" file 
> watching. FSEvents allows for efficient recursive directory watching, which 
> would be a boon for packages like lsp-mode.

Good!

> 1. Write a new backend for filenotify.el. The existing backends explicitly 
> don't support recursive watching, so I'm not sure if it makes sense to have 
> one special backend that does support recursive watching.

This is probably the way to go, but some careful interface design is necessary. 
For example, FSEvents only reports the directory where changes occurred. For 
some applications this may be sufficient, but for others, the exact file names 
are required. What about lsp-mode? Without a specific application in mind, we 
risk over-engineering.

FSEvents can probably co-exist with kqueue which fits the filenotify model 
better for watching individual files, but it would be nice to have something 
that scales better (kqueue uses up file descriptors). On the other hand, 
FSEvents may require careful filtering to avoid being swamped with 
notifications during periods of intensive file system change.