Add functions get_utf8_{string,char}_width().

src/fe-common/core/utf8.c

@@ -22,5 +22,56 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
+#include <glib.h>
 #include "module.h"
 
+/*
+ * Return the width (number of columns when displayed) of the character pointed
+ * by c.
+ */
+int get_utf8_char_width(const gchar *c) {
+	gunichar uc;
+	int char_width;
+	uc = g_utf8_get_char(c);
+	char_width = g_unichar_isprint(uc) ? (1 + g_unichar_iswide(uc)) : 0;
+	return char_width;
+}
+
+/*
+ * Return the number of columns taken by the s string, assuming its end is
+ * marked with a '\0' character and assuming it is a UTF-8 (multibyte) string.
+ * If s is NULL, this function returns -1.
+ * By default, this function takes care to validate s by calling
+ * g_utf8_validate(s, -1, NULL). If this check is deemed unnecessary, passing a
+ * non-zero value as skip_validation will skip that step. If the validation
+ * fails, this function returns -1. Otherwise, it will strive to provide a
+ * value as close as possible to what is expected.
+ */
+int get_utf8_string_width(const gchar *s, int skip_validation) {
+	const gchar *c;
+	int str_width;
+
+	/* Ensure s is non-NULL: */
+	if (!s) {
+		return -1;
+	}
+
+	/* Validate the string, unless required otherwise: */
+	if (!skip_validation) {
+		if (!g_utf8_validate(s, -1, NULL)) {
+			/* Another possibility here would be to return strlen(s). */
+			return -1;
+		}
+	}
+
+	/* Iterate over characters to determine the width: */
+	str_width = 0;
+	for (c = s; *c; c = g_utf8_next_char(c)) {
+		str_width += get_utf8_char_width(c);
+	}
+	/* Note: there probably are some Unicode subtleties (Fitzpatrick
+	 * modifiers?) that make the above implementation somewhat naive, but we
+	 * have to start somewhere.
+	 */
+	return str_width;
+}

src/fe-common/core/utf8.h

@@ -11,6 +11,10 @@
 /* Returns width for character (0-2). */
 int mk_wcwidth(unichar c);
 
+/* Return the number of columns occupied by a given string. */
+int get_utf8_char_width(const gchar *);
+int get_utf8_string_width(const gchar *);
+
 #define unichar_isprint(c) (((c) & ~0x80) >= 32)
 #define is_utf8_leading(c) (((c) & 0xc0) != 0x80)