wallpaper: replace lua timer by a systemd timer

rc.lua

@@ -63,7 +63,6 @@ loadrc("appearance")		-- theme and appearance settings
 loadrc("debug")			-- debugging primitive `dbg()`
 
 loadrc("bindings")		-- keybindings
-loadrc("wallpaper")		-- wallpaper settings
 loadrc("widgets")		-- widgets configuration
 loadrc("tags")			-- tags handling
 loadrc("xlock")			-- lock screen

rc/wallpaper.lua

@@ -1,25 +0,0 @@
--- Change wallpaper
-
-local wtimer = timer { timeout = 0 }
-
-config.wallpaper = {}
-config.wallpaper.directory = awful.util.getdir("config") .. "/wallpapers"
-config.wallpaper.current = awful.util.getdir("cache") .. "/current-wallpaper.png"
-
--- We use fvwm-root because default backend for awsetbg does not seem
--- to accept to set multiscreen wallpapers.
-local change = function()
-   awful.util.spawn_with_shell(
-      awful.util.getdir("config") .. "/bin/build-wallpaper " ..
-	 "--crop --directory " .. config.wallpaper.directory ..
-	 " --target " .. config.wallpaper.current ..
-	 "&& fvwm-root -r " .. config.wallpaper.current)
-end
-
-wtimer:add_signal("timeout", function()
-		     change()
-		     wtimer:stop()
-		     wtimer.timeout = math.random(3000, 3600)
-		     wtimer:start()
-			     end)
-wtimer:start()

systemd/awesome@.service

@@ -6,6 +6,7 @@ After=compton@%i.service
 After=xsettingsd@%i.service
 After=tmux.service
 Before=nm-applet@%i.service
+Before=wallpaper@%i.service
 
 [Service]
 Environment=DISPLAY=%I

systemd/graphical-session@.target

@@ -1,14 +1,16 @@
 [Unit]
 Description=Graphical user session for %I
 StopWhenUnneeded=yes
-Wants=awesome@%i.service
 Wants=autorandr@%i.service
+Wants=awesome@%i.service
 Wants=compton@%i.service
 Wants=inputplug@%i.service
 Wants=misc-x@%i.service
 Wants=nm-applet@%i.service
 Wants=policykit-agent@%i.service
 Wants=redshift@%i.service
+Wants=wallpaper@%i.service
+Wants=wallpaper@%i.timer
 Wants=xiccd@%i.service
 Wants=xsettingsd@%i.service
 Wants=xss-lock@%i.service

systemd/wallpaper@.service

@@ -0,0 +1,14 @@
+[Unit]
+Description=Build a wallpaper for %I
+PartOf=graphical-session@%i.target
+
+[Service]
+Environment=DISPLAY=%I
+Environment=WALLPAPER_DIRECTORY=%h/.config/awesome/wallpapers
+Environment=WALLPAPER_OUTPUT=%h/.cache/awesome/current-wallpaper.png
+ExecStart=%h/.config/awesome/bin/build-wallpaper --crop \
+                                                 --directory $WALLPAPER_DIRECTORY \
+                                                 --target $WALLPAPER_OUTPUT
+ExecStart=/usr/bin/fvwm-root -r $WALLPAPER_OUTPUT
+Type=oneshot
+RemainAfterExit=false

systemd/wallpaper@.timer

@@ -0,0 +1,7 @@
+[Unit]
+Description=Wallpaper rotation for %I
+PartOf=graphical-session@%i.target
+
+[Timer]
+OnUnitActiveSec=1h
+RandomizedDelaySec=10m