fix(term): ansi: StringWidth: properly handle utf8 transitions

exp/term/ansi/width.go

@@ -19,8 +19,12 @@ func Strip(s string) string {
 	// This implements a subset of the Parser to only collect runes and
 	// printable characters.
 	for i := 0; i < len(s); i++ {
-		state, action := Table.Transition(pstate, s[i])
-		// log.Printf("pstate: %s, state: %s, action: %s, code: %c", StateNames[pstate], StateNames[state], ActionNames[action], s[i])
+		var state, action byte
+		if pstate != Utf8State {
+			state, action = Table.Transition(pstate, s[i])
+		}
+
+		// log.Printf("pstate: %s, state: %s, action: %s, code: %c, buf: %q", StateNames[pstate], StateNames[state], ActionNames[action], s[i], buf.String())
 		switch {
 		case pstate == Utf8State:
 			// During this state, collect rw bytes to form a valid rune in the

exp/term/ansi/width_test.go

@@ -26,6 +26,9 @@ var cases = []struct {
 	{"newline", "hello\nworld", 10},
 	{"tab", "hello\tworld", 10},
 	{"controlnewline", "\x1b[31mhello\x1b[0m\nworld", 10},
+	{"style", "\x1B[38;2;249;38;114mfoo", 3},
+	{"unicode", "\x1b[35m“box”\x1b[0m", 5},
+	{"just_unicode", "Claire‘s Boutique", 17},
 }
 
 func TestStringWidth(t *testing.T) {