Cycling Random Wallpaper Or Xscreensaver

Note : Don't use BOTH functions at the same time, as the screensaver will overwrite the picture!

You will need to seed the random number generator and "pop a few" ( official term from the lua documentation) first. If you don't do this you will always have the same sequence. Add those lines before adding any of the following code snippets :

-- seed and "pop a few"
math.randomseed( os.time())
for i=1,1000 do tmp=math.random(0,1000) end

Change the wallpaper randomly after a (relatively random) time :

add this to your rc.lua

x = 0

-- setup the timer
mytimer = timer { timeout = x }
mytimer:add_signal("timeout", function()

  -- tell awsetbg to randomly choose a wallpaper from your wallpaper directory
  os.execute("awsetbg -T -r /usr/share/wallpapers&")

  -- stop the timer (we don't need multiple instances running at the same time)
  mytimer:stop()

  -- define the interval in which the next wallpaper change should occur in seconds
  -- (in this case anytime between 10 and 20 minutes)
  x = math.random( 600, 1200)

  --restart the timer
  mytimer.timeout = x
  mytimer:start()
end)

-- initial start when rc.lua is first run
mytimer:start()

Use an xscreensaver module as an animated wallpaper and switch to another after some time

(Warning : using transparency with this will result in weird effects and in the worst case scenario you won't see anything but the wallpaper!)

So your CPU is idling most of the time and you want some funky eye candy? Here is your solution : run a screensaver as wallpaper! You will need to install xscreensaver first, then add the following code to your rc.lua :

x= 0

-- setup the timer
mytimer = timer { timeout = x }
mytimer:add_signal("timeout", function()

    -- list the wallpaper you want to use (They can be found in /usr/lib/xscreensaver/) followed by any additional 
    -- parameters you need in a separate array element
    back = { "atlantis", "-whalespeed 826 -size 3027 -count 15",  "substrate", "", "fliptext", "", "glmatrix", "-mode hex" }

    -- kill any screensaver from the list that might be running
    for i=1, table.getn(back),2 do
        os.execute("killall -I ".. back[i] .. " 2> /dev/null")
    end

    -- set the background colour to black (just in case, as sometimes the screensavers seem to keep whatever is in the videobuffer)
    os.execute("xsetroot -bg black")

    -- select a new screensaver
    y = math.random( 1, (table.getn(back)/2))-1
    os.execute( "/usr/lib/xscreensaver/" .. back[ (y*2) + 1] .. " -root " .. back[ (y*2) + 2] .. "&")

    -- define the interval in which the next wallpaper change should occur in seconds
    -- (in this case anytime between 10 and 20 minutes)
    x = math.random( 600, 1200)

    -- reset the timer
    mytimer:stop()
    mytimer.timeout = x
    mytimer:start()
end)

-- initial start on the first run
mytimer:start()

Toggle the timer on and off

You will probably need a way to toggle the timer on and off. Add this block to mymainmenu in the default rc.lua to do that for the xscreensaver timer :

{ "toggle wallpaper", function()

     -- check whether the timer is running
     if mytimer.started then
        -- stop and set the timer to 0
	mytimer:stop() 
	mytimer.timeout = 0
        -- kill any running xscreensaver from the list used earlier on (no need for the parameters this time)
	back = { "atlantis",  "substrate", "fliptext", "glmatrix" }
	for i=1, table.getn(back) do
	    os.execute("killall -I ".. back[i] .. " 2> /dev/null")
        end                                                        
        -- optionally set a random static wallpaper 
        os.execute("awsetbg -T -r /usr/share/wallpapers&")                                                                  
     else
        -- reset and restart the timer
	mytimer.timeout = 0
	mytimer:start()
     end
  end
},

Writing a toggle for the static wallpaper timer is similar (but much shorter)