[polybar] Refactor music display module

Refactored music module to use a constant tail output of the underlying
script, to enable mode-switching, and to allow playing or pausing the
current song.

polybar/.config/polybar/config

@@ -54,7 +54,7 @@ padding-right = 0
 module-margin-left = 2
 
 modules-left = workspaces
-modules-center = mprisdisplay date papersdue
+modules-center = music date papersdue
 modules-right = networkspeed archupdates cpu temp backlight volume battery
 ; do not use offsets for the bar, would only work with override-redirect
 ; and will mess up tray https://github.com/polybar/polybar/issues/1355
@@ -207,6 +207,17 @@ date-alt = %A, %d %B %Y (W %V)
 time-alt = %H:%M
 label = %date% %{T2} %{T-}%time%
 
+; display information on currently playing track, allows simple track manipulation
+[module/music]
+type = custom/script
+exec = $XDG_CONFIG_HOME/polybar/scripts/poly-mprisdisplay
+exec-if = type $XDG_CONFIG_HOME/polybar/scripts/poly-mprisdisplay
+tail = true
+click-left = kill -USR1 %pid%
+click-right = kill -USR2 %pid%
+; TODO: add album art display (on click?) - retrieved by playerctl metadata mpris:artUrl
+
+; display information on remaining papers to read for the upcoming week
 [module/papersdue]
 type = custom/script
 exec = $XDG_BIN_HOME/bib_due $BIBFILE | wc -l
@@ -231,13 +242,6 @@ type = custom/script
 exec = $XDG_CONFIG_HOME/polybar/scripts/poly-networkspeed
 tail = true
 
-[module/mprisdisplay]
-type = custom/script
-exec = $XDG_CONFIG_HOME/polybar/scripts/poly-mprisdisplay
-interval = 3
-click-left = playerctl play-pause &
-; TODO: add album art display (on click?) - retrieved by playerctl metadata mpris:artUrl
-
 [module/volume]
 type = internal/pulseaudio
 ; Available tags:

polybar/.config/polybar/scripts/poly-mprisdisplay

@@ -1,11 +1,47 @@
 #!/bin/sh
+# script to echo the current playback situation
+#
+# call without args to return playing symbol or empty, depending on current playback status
+# call with 1 to return 'artist -  title' metadata (verbose mode)
+# send SIGUSR2 signal to toggle pause/playing state of song (e.g. kill -USR2 %PID)
+#
+# depends on playerctl being installed
 
-player_status=$(playerctl status 2>/dev/null)
+exist playerctl low "polybar music" || exit 1
 
-if [ "$player_status" = "Playing" ]; then
-  echo "ﱘ $(playerctl metadata artist) - $(playerctl metadata title)"
-elif [ "$player_status" = "Paused" ]; then
-  echo "  $(playerctl metadata artist) - $(playerctl metadata title)"
-else
-  echo ""
-fi
+mode=${1:-0}
+update_time=1
+symbol_playing=""
+symbol_paused=""
+
+modetoggle() {
+  mode=$(((mode + 1) % 2))
+}
+trap "modetoggle" USR1
+
+playpause() {
+  playerctl play-pause
+}
+trap "playpause" USR2
+
+decorate() {
+  if [ "$player_status" = "Playing" ]; then
+    echo "${symbol_playing}$1"
+  elif [ "$player_status" = "Paused" ]; then
+    echo "${symbol_paused}$1"
+  else
+    echo ""
+  fi
+}
+
+while true; do
+  player_status=$(playerctl status 2>/dev/null)
+
+  if [ $mode -eq 0 ]; then
+    decorate ""
+  elif [ $mode -eq 1 ]; then
+    decorate " $(playerctl metadata artist) - $(playerctl metadata title)"
+  fi
+  sleep $update_time &
+  wait
+done