Subject: [PATCH] Don't poll auto-revert files that use notification
From: Mattias Engdegård <[email-masked]>
To: [email-masked]
Cc: Michael Albinus <[email-masked]>
Date: Wed, 24 Apr 2019 20:14:46 +0200
List-Id: <debbugs-submit.debbugs.gnu.org>

It is a waste of power, on battery-powered devices in particular, to poll files in auto-revert mode periodically when change notification is used. The change is straightforward (attached patch); the main concern is whether the notification system is reliable enough.

In general, it probably is. There is a comment in w32notify.c about SMB-mounted file systems from Samba servers; while Samba does support notification nowadays, there are probably older systems still be deficient in that regard. However, isn't this what `auto-revert-notify-exclude-dir-regexp' is for? I'm not familiar with the way Emacs is used on Windows, but would adding something like

 (rx bos
     (or "\\\\" "//")
     (one-or-more (not (any "/:\\")))
     (any "/\\"))

to `auto-revert-notify-exclude-dir-regexp' be a good start?

Another note about what this patch does not do: global-auto-revert-mode will still use polling. This could be added later on, if there is a good place to hook into for buffer creation.