Control media players with playerctl from media keys and headphones

Run playerctld as a dbus unit with Restart=on-failure, start it through that
unit on D-Bus activation, tie mpris-proxy to it, and bind the XF86 media keys
to playerctl in xmonad.

.config/systemd/user/mpris-proxy.service.d/mpris-proxy-after-mpd.conf

@@ -1,2 +0,0 @@
-[Unit]
-After=mpd-mpris.service

.config/systemd/user/mpris-proxy.service.d/override.conf

@@ -0,0 +1,4 @@
+[Unit]
+Wants=playerctld.service
+After=playerctld.service mpDris2.service
+PartOf=playerctld.service

.config/systemd/user/playerctld.service.d/override.conf

@@ -0,0 +1,5 @@
+[Service]
+Type=dbus
+ExecStart=
+ExecStart=/usr/bin/playerctld
+Restart=on-failure

.config/xmonad/xmonad.hs

@@ -137,6 +137,11 @@ myConfig =
     `additionalKeys` [ ((0, xF86XK_AudioMute), spawn "pactl set-sink-mute $(pactl get-default-sink) toggle"),
                        ((0, xF86XK_AudioLowerVolume), spawn "pactl set-sink-volume $(pactl get-default-sink) -10%"),
                        ((0, xF86XK_AudioRaiseVolume), spawn "wpctl set-volume -l 1.0 @DEFAULT_AUDIO_SINK@ 10%+"),
+                       ((0, xF86XK_AudioPlay), spawn "playerctl play-pause"),
+                       ((0, xF86XK_AudioPause), spawn "playerctl pause"),
+                       ((0, xF86XK_AudioStop), spawn "playerctl stop"),
+                       ((0, xF86XK_AudioNext), spawn "playerctl next"),
+                       ((0, xF86XK_AudioPrev), spawn "playerctl previous"),
                        ((0, xF86XK_Calculator), spawn "qalculate-gtk"),
                        ((0, xF86XK_HomePage), spawn myBrowser),
                        ((0, xF86XK_Mail), namedScratchpadAction myScratchpads "Mail"),

.local/share/dbus-1/services/org.mpris.MediaPlayer2.playerctld.service

@@ -0,0 +1,4 @@
+[D-BUS Service]
+Name=org.mpris.MediaPlayer2.playerctld
+Exec=/usr/bin/playerctld
+SystemdService=playerctld.service