feat(presence-detect): skip the camera entirely during a manual caffeine session

When idle is inhibited manually (a caffeine toggle, not this daemon), the lock
is held regardless of presence, so polling the camera is pointless. Guard the
loop: if the shared idle lock is alive but we don't own it (same test as
caffeine-manual-status.sh), skip the read and leave the camera free for other
apps for the whole manual session. PRESENCE_FLAG is cleared while skipping,
since we're no longer watching — so the widget's presence input reads false
during a manual session instead of showing a stale "camera sees you".

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

desktopenvs/hyprlua/scripts/presence-detect.sh

@@ -30,11 +30,12 @@ PID_FILE="/tmp/caffeine-inhibit.pid"
 # Marks that *this daemon* (not the manual caffeine toggle) currently holds
 # the lock, so a "no motion" tick never releases a manually-started session.
 OWNED_FLAG="/tmp/presence-inhibit-owned"
-# Records whether the camera currently SEES the user (motion on the last tick),
-# INDEPENDENT of who holds the idle lock. Unlike OWNED_FLAG this is set even when
-# a manual caffeine session already owns the lock (so the daemon never starts its
-# own inhibitor). presence-status.sh reads this so the Eww widget can show the
-# presence input as a distinct signal from a manual caffeine toggle.
+# Records whether the camera currently SEES the user (motion, or the camera
+# being in use by another app, on the last tick). presence-status.sh reads this
+# so the Eww widget can show presence as a distinct signal from the idle lock.
+# It reflects live camera state only while the daemon is actively watching:
+# during a MANUAL caffeine session the daemon stops reading the camera entirely
+# (to leave it free) and clears this flag, so presence reads false there.
 PRESENCE_FLAG="/tmp/presence-detected"
 PRESENCE_CFG="${XDG_CONFIG_HOME:-$HOME/.config}/presence-detect.conf"
 
@@ -133,6 +134,18 @@ trap _cleanup SIGTERM SIGINT SIGHUP
 LAST_MOTION=0
 
 while true; do
+    # When idle is inhibited MANUALLY (a caffeine toggle, not this daemon), the
+    # lock is already held regardless of presence, so there's no reason to look
+    # at the camera — skip the read entirely and leave the device free for other
+    # apps. Detected the same way caffeine-manual-status.sh does it: the shared
+    # lock is alive but we don't own it. We clear PRESENCE_FLAG because we're no
+    # longer watching and must not report a stale "camera sees you".
+    if _inhibit_running && [[ ! -f "$OWNED_FLAG" ]]; then
+        rm -f "$PRESENCE_FLAG"
+        sleep "$(_next_interval)"
+        continue
+    fi
+
     DEVICE="$(_camera_id)"
     # Run the OpenCV motion detector; stderr suppressed to keep the journal clean.
     python3 "$PYTHON_DETECT" "$DEVICE" 2>/dev/null
@@ -143,9 +156,6 @@ while true; do
         # another app (a video call, howdy) is holding the camera, which is
         # itself proof you're here, so it keeps the session awake even though we
         # can't read frames. Both refresh the grace clock and mark presence.
-        # PRESENCE_FLAG is updated *independently* of the inhibit lock — it
-        # reflects "user is present" even during a manual caffeine session (where
-        # _start_inhibit is a no-op because the lock is already held).
         0|3) LAST_MOTION="$now"; touch "$PRESENCE_FLAG"; _start_inhibit ;;
         # No motion: only actually release once we've been still for the whole
         # grace window. Within it, leave the flag/lock exactly as they were so a

desktopenvs/hyprlua/scripts/presence-status.sh

@@ -3,10 +3,11 @@
 # presence-detect daemon currently sees the user (motion on its last tick),
 # INDEPENDENT of whether the idle lock is held or who holds it.
 #
-# presence-detect.sh writes PRESENCE_FLAG on every "motion" tick and removes it
-# on every "no motion" tick, so this is a clean, standalone signal — true even
-# during a manual caffeine session (where the daemon never starts its own
-# inhibitor). For the MANUAL-inhibit input, see caffeine-manual-status.sh.
+# presence-detect.sh writes PRESENCE_FLAG on every "present" tick and removes it
+# on every "away" tick, so this is a clean, standalone signal. Note: during a
+# MANUAL caffeine session the daemon stops reading the camera (to leave it free)
+# and clears the flag, so presence reads false there. For the MANUAL-inhibit
+# input, see caffeine-manual-status.sh.
 #
 # Prints "true" when presence is detected, else "false".
 PRESENCE_FLAG="/tmp/presence-detected"