perf: accelerate printable ASCII text width

src/utils.rs

@@ -115,6 +115,12 @@ pub fn set_true_colors_enabled_stderr(val: bool) {
 pub fn measure_text_width(s: &str) -> usize {
     #[cfg(feature = "ansi-parsing")]
     {
+        let printable_ascii = s
+            .bytes()
+            .fold(true, |ok, b| ok & (0x20..=0x7e).contains(&b));
+        if printable_ascii {
+            return s.len();
+        }
         AnsiCodeIterator::new(s)
             .filter_map(|(s, is_ansi)| match is_ansi {
                 false => Some(str_width(s)),
@@ -1261,3 +1267,37 @@ fn test_truncate_str_multibyte_no_panic() {
     assert_eq!(&truncate_str(s, 5, ""), s);
     assert_eq!(&truncate_str("ab\u{4f60}cd", 3, ""), "ab\u{4f60}");
 }
+
+#[cfg(all(feature = "std", feature = "ansi-parsing", feature = "unicode-width"))]
+#[test]
+fn printable_ascii_uses_width() {
+    assert_eq!(measure_text_width(""), 0);
+    assert_eq!(measure_text_width(" !~"), 3);
+}
+
+#[cfg(all(feature = "std", feature = "ansi-parsing", feature = "unicode-width"))]
+#[test]
+fn controls_and_ansi_fall_back_to_parser() {
+    // Existing str_width counts the newline as one column in this contract.
+    assert_eq!(measure_text_width("a\nb"), 3);
+    assert_eq!(measure_text_width("\x1b[31mred\x1b[0m"), 3);
+    assert_eq!(measure_text_width("\u{9b}31mred\u{9b}0m"), 3);
+}
+
+#[cfg(all(feature = "std", feature = "ansi-parsing", feature = "unicode-width"))]
+#[test]
+fn unicode_width_falls_back() {
+    assert_eq!(measure_text_width("é"), 1);
+    assert_eq!(measure_text_width("e\u{301}"), 1);
+    assert_eq!(measure_text_width("1\u{fe0f}\u{20e3}"), 2);
+    assert_eq!(measure_text_width("👩‍💻"), 2);
+}
+
+#[cfg(all(feature = "std", feature = "ansi-parsing", feature = "unicode-width"))]
+#[test]
+fn long_ascii_prefix_with_later_control_falls_back() {
+    let mut value = "x".repeat(4096);
+    value.push('\n');
+    value.push('y');
+    assert_eq!(measure_text_width(&value), 4098);
+}