charm cursor: don't exit on eof

charm cursor is meant to be more of a "watcher" it shouldn't choose any particular action on Eof, instead it can just return "unhandled". when in a parallel state, this will cause it to be dropped ( where previously it would have forced a terminal transition ) -- but at Eof the machine is exiting, so that's fine.

charm/charmParallel.go

@@ -1,15 +1,17 @@
 package charm
 
-// Parallel region; run all of the passed states until they all return nil.
-// if any return error, this returns error.
+// Run all of the passed states.
+// If any return nil, they are dropped;
+// If any return Terminal ( ex. via Error() or Finished() )
+// the parallel state exits.
 func Parallel(name string, rs ...State) State {
 	return Self(name, func(self State, r rune) (ret State) {
 		var cnt int
 	Loop:
 		for _, s := range rs {
 			switch next := s.NewRune(r); next.(type) {
 			case nil:
-				// skip
+				// this drops the state from the update list
 			case Terminal:
 				ret = next
 				break Loop

charmed/charmedCursor.go

@@ -10,7 +10,7 @@ func DecodePos(y, x *int) charm.State {
 	return charm.Self("cursor", func(self charm.State, q rune) (ret charm.State) {
 		switch q {
 		case runes.Eof:
-			ret = charm.Finished() // absorb
+			ret = nil // return unhandled; in a parallel state this stops updating
 		case runes.Newline:
 			(*y)++
 			(*x) = 0