Add utf8_fprintf helper that returns correct number of columns

Since command usages can be translated, they may include utf-8
encoded strings, and the output in console may not align well any
more. This is because strlen() is different from strwidth() on utf-8
strings.

A wrapper utf8_fprintf() can help to return the correct number of
columns required.

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Reviewed-by: Torsten Bögershausen <tboegi@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 21 insertions, 0 deletions

diff --git a/utf8.c b/utf8.c
index 5c61bbe113..c7bda66e38 100644
--- a/utf8.c
+++ b/utf8.c
@@ -431,6 +431,27 @@ int same_encoding(const char *src, const char *dst)
 }
 
 /*
+ * Wrapper for fprintf and returns the total number of columns required
+ * for the printed string, assuming that the string is utf8.
+ */
+int utf8_fprintf(FILE *stream, const char *format, ...)
+{
+	struct strbuf buf = STRBUF_INIT;
+	va_list arg;
+	int columns;
+
+	va_start(arg, format);
+	strbuf_vaddf(&buf, format, arg);
+	va_end(arg);
+
+	columns = fputs(buf.buf, stream);
+	if (0 <= columns) /* keep the error from the I/O */
+		columns = utf8_strwidth(buf.buf);
+	strbuf_release(&buf);
+	return columns;
+}
+
+/*
  * Given a buffer and its encoding, return it re-encoded
  * with iconv.  If the conversion fails, returns NULL.
  */