Use channel to receive list of runes insteard of raw array access

layout.go

@@ -154,7 +154,8 @@ func (u UserPrompt) Draw(state *Peco) {
 	default:
 		// the caret is in the middle of the string
 		prev := int(0)
-		for i, r := range q.Runes() {
+		var i int
+		for r := range q.Runes() {
 			fg := u.styles.Query.fg
 			bg := u.styles.Query.bg
 			if i == c.Pos() {
@@ -163,6 +164,7 @@ func (u UserPrompt) Draw(state *Peco) {
 			}
 			u.screen.SetCell(int(u.promptLen+1+prev), int(location), r, fg, bg)
 			prev += int(runewidth.RuneWidth(r))
+			i++
 		}
 		fg := u.styles.Query.fg
 		bg := u.styles.Query.bg

query.go

@@ -69,16 +69,23 @@ func (q *Query) Append(r rune) {
 	q.query = append(q.query, r)
 }
 
-// Runes returns a copy of the underlying query as an array of runes.
-func (q *Query) Runes() []rune {
+// Runes returns a channel that gives you the list of runes in the query
+func (q *Query) Runes() <-chan rune {
 	q.mutex.Lock()
 	defer q.mutex.Unlock()
-	ret := make([]rune, len(q.query))
-	copy(ret, q.query)
+	c := make(chan rune, len(q.query))
 
-	// Because this is a copy, the user of this function does not need
-	// to know about locking and stuff
-	return ret
+	go func() {
+		defer close(c)
+		q.mutex.Lock()
+		defer q.mutex.Unlock()
+
+		for _, r := range q.query {
+			c<-r
+		}
+	}()
+
+	return c
 }
 
 func (q *Query) RuneAt(where int) rune {