Pause dunst while the screen is locked; add notification history keys

screen-lock holds notifications until unlock, and M-S-l now goes through
loginctl lock-session so it uses the same locker. M-S-n pops dunst history,
M-C-n closes all notifications.

.config/xmonad/xmonad.hs

@@ -118,7 +118,9 @@ myConfig =
       logHook = myLogHook
     }
     `additionalKeysP` [ ("M-b", sendMessage ToggleStruts),
-                        ("M-S-l", spawn "slock"),
+                        ("M-S-l", spawn "loginctl lock-session"),
+                        ("M-S-n", spawn "dunstctl history-pop"),
+                        ("M-C-n", spawn "dunstctl close-all"),
                         ("<Print>", unGrab *> spawn ("scrot " ++ myScreenshotDir ++ myScreenshotName)),
                         ("S-<Print>", unGrab *> spawn ("scrot -s " ++ myScreenshotDir ++ myScreenshotName)),
                         ("M-S-<Print>", unGrab *> spawn ("scrot -u " ++ myScreenshotDir ++ myScreenshotName)),

.local/bin/screen-lock

@@ -3,12 +3,24 @@
 
 image=/usr/share/backgrounds/arch_1920x1080.png
 
+# Hold notifications while locked; dunst shows them on unlock. A signal to this
+# script is passed on to i3lock, as the old exec did.
+was_paused=$(dunstctl is-paused 2>/dev/null)
+dunstctl set-paused true 2>/dev/null
+trap 'kill "$pid" 2>/dev/null' INT TERM HUP
+
 # -n: stay in the foreground, as xss-lock needs to see when the screen is unlocked.
 # --indicator keeps the ring (and the layout text) visible before typing.
 # The layout's default spot (dx:dy+30) falls inside the ring: put it below.
-exec i3lock -n -i "$image" -F -c 000000ff \
+i3lock -n -i "$image" -F -c 000000ff \
     -e -f --indicator --keylayout 0 \
     --layout-pos='ix:iy+r+40' --layout-color=ffffffff \
     --layout-size=24 \
     --time-color=ffffffff --date-color=ffffffff --date-str='%A, %d %B' \
-    --ring-color=1793d1ff --line-uses-ring "$@"
+    --ring-color=1793d1ff --line-uses-ring "$@" &
+pid=$!
+# A trapped signal interrupts the first wait; the second waits for i3lock to exit.
+wait "$pid"
+wait "$pid" 2>/dev/null
+
+[ "$was_paused" = true ] || dunstctl set-paused false 2>/dev/null