widget: display a minimal tasklist for one-screen setups

We do not have enough space for a complete tasklist on one-screen
setups. Therefore, we just display a minimal ones with just
icons. Since this does not take much space, we display icons for all
tags.

rc/widgets.lua

@@ -173,10 +173,13 @@ for s = 1, screen.count() do
     promptbox[s] = awful.widget.prompt({ layout = awful.widget.layout.horizontal.leftright })
     layoutbox[s] = awful.widget.layoutbox(s)
     awful.widget.layout.margins[layoutbox[s]] = { left = 5 }
-    if screen.count() > 1 then
     tasklist[s]  = awful.widget.tasklist(
        function(c)
-	     local title, color, _, icon = awful.widget.tasklist.label.currenttags(c, s)
+	  local fn = awful.widget.tasklist.label.currenttags
+	  if screen.count() == 1 then
+	     fn = awful.widget.tasklist.label.alltags
+	  end
+	  local title, color, _, icon = fn(c, s)
 	  -- Try to search for an alternative icon if none is available
 	  for _, name in pairs({c.class, c.instance}) do
 	     if not icon and title and name then
@@ -195,11 +198,12 @@ for s = 1, screen.count() do
 	     end
 	  end
 	  -- Use our icon and don't set the status image.
+	  if screen.count() > 1 then
 	     return title, color, nil, icon
-	  end, tasklist.buttons)
-    else
-       tasklist[s] = ""
+	  elseif icon then
+	     return "", color, nil, icon
 	  end
+       end, tasklist.buttons)
 
     -- Create the taglist
     taglist[s]   = sharetags.taglist(s, sharetags.label.all, taglist.buttons)
@@ -230,7 +234,7 @@ for s = 1, screen.count() do
 	on(1, netgraph.widget), on(1, netwidget), on(1, separator),
 	on(1, memwidget), on(1, separator),
 	on(1, cpuwidget), on(1, separator),
-	tasklist[s], tasklist[s] ~= "" and separator or "",
+	tasklist[s], separator,
 	layout = awful.widget.layout.horizontal.rightleft }
 end