xrandr: Add (some) --setprovider* arg completion support

completions/xrandr

@@ -45,6 +45,13 @@ _xrandr()
             COMPREPLY=( $( compgen -W 'normal inverted left right' -- "$cur" ) )
             return
             ;;
+        --setprovideroutputsource|--setprovideroffloadsink)
+            local providers=$( "$1" --listproviders 2>/dev/null |
+                sed -ne 's/.* name:\([^ ]*\).*/\1/p' )
+            COMPREPLY=( $( compgen -W "$providers" -- "$cur" ) )
+            # TODO 2nd arg needed, is that a provider as well?
+            return
+            ;;
     esac
 
     COMPREPLY=( $( compgen -W '$( "$1" -help 2>&1 |