1 files changed, 73 insertions, 0 deletions
diff --git a/lib/wcwidth.c b/lib/wcwidth.c
new file mode 100644
index 0000000..6af212b
--- /dev/null
+++ b/lib/wcwidth.c
@@ -0,0 +1,73 @@
+/* Determine the number of screen columns needed for a character.
+   Copyright (C) 2006-2007, 2010-2020 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+
+/* Specification.  */
+#include <wchar.h>
+
+/* Get iswprint.  */
+#include <wctype.h>
+
+#include "localcharset.h"
+#include "streq.h"
+#include "uniwidth.h"
+
+/* Returns 1 if the current locale is an UTF-8 locale, 0 otherwise.  */
+static inline int
+is_locale_utf8 (void)
+{
+  const char *encoding = locale_charset ();
+  return STREQ_OPT (encoding, "UTF-8", 'U', 'T', 'F', '-', '8', 0, 0, 0, 0);
+}
+
+#if GNULIB_WCHAR_SINGLE
+/* When we know that the locale does not change, provide a speedup by
+   caching the value of is_locale_utf8.  */
+static int cached_is_locale_utf8 = -1;
+static inline int
+is_locale_utf8_cached (void)
+{
+  if (cached_is_locale_utf8 < 0)
+    cached_is_locale_utf8 = is_locale_utf8 ();
+  return cached_is_locale_utf8;
+}
+#else
+/* By default, don't make assumptions, hence no caching.  */
+# define is_locale_utf8_cached is_locale_utf8
+#endif
+
+int
+wcwidth (wchar_t wc)
+#undef wcwidth
+{
+  /* In UTF-8 locales, use a Unicode aware width function.  */
+  if (is_locale_utf8_cached ())
+    {
+      /* We assume that in a UTF-8 locale, a wide character is the same as a
+         Unicode character.  */
+      return uc_width (wc, "UTF-8");
+    }
+  else
+    {
+      /* Otherwise, fall back to the system's wcwidth function.  */
+#if HAVE_WCWIDTH
+      return wcwidth (wc);
+#else
+      return wc == 0 ? 0 : iswprint (wc) ? 1 : -1;
+#endif
+    }
+}