Keep inhibits across daemon restarts

Save held inhibits to $XDG_RUNTIME_DIR/xautolock-inhibit.json and restore them on start if the previous instance stopped within --restore-window (default 30s) on the same bus and the senders are still connected. The file is touched every 10s while inhibits are held, so crashes are timed too.

README.md

@@ -16,6 +16,7 @@ xautolock stays your locker; xautolock-inhibit only switches it off and on.
 - Runs `xautolock` only when the number of active requests goes from 0 to 1 or back to 0. Re-enabling waits a few seconds (`--release-delay`), because browsers send short bursts of requests when a video starts.
 - Pauses X blanking with `XScreenSaverSuspend`, the same mechanism mpv uses, instead of changing `xset` settings. The X server ends the pause by itself if the daemon exits or crashes.
 - Requests whose reason is on an ignore list (default: `Playing audio`) are accepted and logged, but don't block locking. Firefox-based browsers send one for audio playback, which would otherwise keep the screen unlocked while music plays with nobody at the computer.
+- Keeps the requests it holds in `$XDG_RUNTIME_DIR/xautolock-inhibit.json`, so a restarted or crashed daemon takes them over. They are taken over only if the previous daemon stopped at most 30 seconds ago (`--restore-window`) on the same session bus, and only for clients still connected. A request released while no daemon was running can't be seen, so an old file isn't trusted.
 - On exit (including SIGTERM), it re-enables xautolock. The systemd unit also runs `xautolock -enable` when it stops, as a fallback.
 - If another program (a desktop environment) already owns `org.freedesktop.ScreenSaver`, it exits with status 2 instead of taking over.
 
@@ -45,12 +46,13 @@ The unit has no `[Install]` section on purpose. Enabling it at login would also
 ## Usage
 
 ```
-xautolock-inhibit [-i REASON] [--count-all] [-d SECONDS]
+xautolock-inhibit [-i REASON] [--count-all] [-d SECONDS] [--restore-window SECONDS]
 ```
 
 - `-i`, `--ignore-reason REASON`: request reason that doesn't block locking. Can be repeated; replaces the default (`Playing audio`).
 - `--count-all`: every request blocks locking; no reasons are ignored.
 - `-d`, `--release-delay SECONDS`: wait this long after the last release before re-enabling xautolock (default 5).
+- `--restore-window SECONDS`: take over requests from a previous daemon that stopped at most this long ago (default 30; 0 disables).
 
 To change the options used by the service:
 
@@ -84,7 +86,7 @@ journalctl --user -u xautolock-inhibit
 
 ## Limitations
 
-- Restarting the daemon loses the requests it holds; apps don't send them again. Avoid restarting it while a video or game is running.
+- A release sent while the daemon is down is lost: if the daemon is back within `--restore-window`, that request stays active until its app exits. After a longer stop, all held requests are dropped and apps don't send them again.
 - `SimulateUserActivity` is accepted but does nothing. Calls are logged once when a client starts sending them and once, with a count, after 5 minutes without any.
 - `GetActive` always returns `false`.