Trim trailing whitespaces after processing ANSI sequences

Close #4282

src/core.go

@@ -135,6 +135,7 @@ func Run(opts *Options) (int, error) {
 				return false
 			}
 			item.text, item.colors = ansiProcessor(stringBytes(transformed))
+			item.text.TrimTrailingWhitespaces()
 			item.text.Index = itemIndex
 			item.origText = &data
 			itemIndex++

src/options.go

@@ -778,7 +778,7 @@ func nthTransformer(str string) (func(Delimiter) func([]Token, int32) string, er
 		}
 		return func(Delimiter) func([]Token, int32) string {
 			return func(tokens []Token, index int32) string {
-				return strings.TrimRightFunc(JoinTokens(Transform(tokens, nth)), unicode.IsSpace)
+				return JoinTokens(Transform(tokens, nth))
 			}
 		}, nil
 	}

src/util/chars.go

@@ -184,6 +184,11 @@ func (chars *Chars) TrailingWhitespaces() int {
 	return whitespaces
 }
 
+func (chars *Chars) TrimTrailingWhitespaces() {
+	whitespaces := chars.TrailingWhitespaces()
+	chars.slice = chars.slice[0 : len(chars.slice)-whitespaces]
+}
+
 func (chars *Chars) TrimSuffix(runes []rune) {
 	lastIdx := len(chars.slice)
 	firstIdx := lastIdx - len(runes)