xrandr: add a xrandr menu bound to XF86Display

rc.lua

@@ -78,5 +78,6 @@ loadrc("xlock")			-- lock screen
 loadrc("signals")		-- window manager behaviour
 loadrc("rules")			-- window rules
 loadrc("quake")			-- quake console
+loadrc("xrandr")		-- xrandr menu
 
 root.keys(config.keys.global)

rc/xrandr.lua

@@ -0,0 +1,89 @@
+-- Menu with xrandr choices
+
+-- Get active outputs
+local function outputs()
+   local outputs = {}
+   local xrandr = io.popen("xrandr -q")
+   if xrandr then
+      for line in xrandr:lines() do
+	 output = line:match("^([%w-]+) connected ")
+	 if output then
+	    outputs[#outputs + 1] = output
+	 end
+      end
+      xrandr:close()
+   end
+
+   return outputs
+end
+
+local function arrange(out)
+   -- We need to enumerate all the way to combinate output. We assume
+   -- we want only an horizontal layout.
+   local choices  = {}
+   local previous = { {} }
+   for i = 1, #out do
+      -- Find all permutation of length `i`: we take the permutation
+      -- of length `i-1` and for each of them, we create new
+      -- permutations by adding each output at the end of it if it is
+      -- not already present.
+      local new = {}
+      for _, p in pairs(previous) do
+	 for _, o in pairs(out) do
+	    if not awful.util.table.hasitem(p, o) then
+	       new[#new + 1] = awful.util.table.join(p, {o})
+	    end
+	 end
+      end
+      choices = awful.util.table.join(choices, new)
+      previous = new
+   end
+
+   return choices
+end
+
+-- Display xrandr menu
+local function menu()
+   local menu = {}
+   local out = outputs()
+   local choices = arrange(out)
+
+   for _, choice in pairs(choices) do
+      local cmd = "xrandr"
+      -- Enabled outputs
+      for i, o in pairs(choice) do
+	 cmd = cmd .. " --output " .. o .. " --auto"
+	 if i > 1 then
+	    cmd = cmd .. " --right-of " .. choice[i-1]
+	 end
+      end
+      -- Disabled outputs
+      for _, o in pairs(out) do
+	 if not awful.util.table.hasitem(choice, o) then
+	    cmd = cmd .. " --output " .. o .. " -off"
+	 end
+      end
+
+      local label = ""
+      if #choice == 1 then
+	 label = 'Only ' .. choice[1]
+      else
+	 for i, o in pairs(choice) do
+	    if i > 1 then label = label .. ", " end
+	    label = label .. o
+	 end
+      end
+
+      menu[#menu + 1] = { " " .. label,
+			  function() awful.util.spawn(cmd, false) end,
+			  "/usr/share/icons/gnome/32x32/devices/display.png" }
+   end
+
+   -- Show the menu
+   awful.menu({ items = menu,
+		width = 300 }):show({ keygrabber = true })
+end
+
+config.keys.global = awful.util.table.join(
+   config.keys.global,
+   awful.key({}, "XF86Display", menu))