fix(ansi): width: always use grapheme finder for width calculation

aymanbagabas · aymanbagabas · commit 6921c759c913 · 2026-04-13T12:50:52.000-04:00
When we're encountering half-width characters, or joining characters,
it's important that we use the grapheme cluster finder to determine the
width of the string. For example, an ASCII + a joining character is a
single grapheme, but we used to treat it as two separate characters,
which caused the width to be incorrectly calculated as 2 instead of 1.
diff --git a/ansi/width.go b/ansi/width.go
@@ -87,7 +87,7 @@ func stringWidth(m Method, s string) int {
 
 	for i := 0; i < len(s); i++ {
 		state, action := parser.Table.Transition(pstate, s[i])
-		if state == parser.Utf8State {
+		if action == parser.PrintAction || state == parser.Utf8State {
 			cluster, w := FirstGraphemeCluster(s[i:], m)
 			width += w
 
diff --git a/ansi/width_test.go b/ansi/width_test.go
@@ -34,6 +34,7 @@ var cases = []struct {
 	{"unclosed_ansi", "Hey, \x1b[7m\n猴", "Hey, \n猴", 7, 7},
 	{"double_asian_runes", " 你\x1b[8m好.", " 你好.", 6, 6},
 	{"flag", "🇸🇦", "🇸🇦", 2, 1},
+	{"half width and ascii", "(ﾟ", "(ﾟ", 1, 1},
 }
 
 func TestStrip(t *testing.T) {

Original file line number	Diff line number	Diff line change
`@@ -34,6 +34,7 @@ var cases = []struct {`
`34`	`34`	`{"unclosed_ansi", "Hey, \x1b[7m\n猴", "Hey, \n猴", 7, 7},`
`35`	`35`	`{"double_asian_runes", " 你\x1b[8m好.", " 你好.", 6, 6},`
`36`	`36`	`{"flag", "🇸🇦", "🇸🇦", 2, 1},`
	`37`	`+ {"half width and ascii", "(ﾟ", "(ﾟ", 1, 1},`
`37`	`38`	`}`
`38`	`39`
`39`	`40`	`func TestStrip(t *testing.T) {`