+
+size_t
+ss_utf8_count_columns (struct substring s)
+{
+ return utf8_count_columns (s.string, s.length);
+}
+
+/* Returns a substring of S starting at 0-based display column START and
+ running for N display columns. */
+struct substring
+ss_utf8_columns (struct substring s, size_t start, size_t n)
+{
+ ss_advance (&s, utf8_columns_to_bytes (s.string, s.length, start));
+ s.length = utf8_columns_to_bytes (s.string, s.length, n);
+ return s;
+}