start: make xrun start apps after awesome is ready

`xrun` is also moved in its own module

rc/xrun.lua

@@ -0,0 +1,33 @@
+-- run a command only if the client does not already exist
+
+local xrun_now = function(name, cmd)
+   -- Try first the list of clients from awesome (which is available
+   -- only if awesome has fully started, therefore, this function
+   -- should be run inside a 0 timer)
+   local clients = client.get()
+   local client
+   for _, client in pairs(clients) do
+      if client.name == name or client.class == name or client.instance == name then
+	 return
+      end
+   end
+
+   -- Not found, let's check with xwininfo. We can only check name but
+   -- we can catch application without a window...
+   if os.execute("xwininfo -name '" .. name .. "' > /dev/null 2> /dev/null") == 0 then
+      return
+   end
+   awful.util.spawn_with_shell(cmd or name)
+end
+
+-- Run a command if not already running.
+xrun = function(name, cmd)
+   -- We need to wait for awesome to be ready. Hence the timer.
+   local stimer = timer { timeout = 0 }
+   local run = function()
+      stimer:stop()
+      xrun_now(name, cmd)
+   end
+   stimer:add_signal("timeout", run)
+   stimer:start()
+end