1 /* Determine the number of screen columns needed for a character.
2 Copyright (C) 2006-2007, 2010-2021 Free Software Foundation, Inc.
3
4 This program is free software: you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation; either version 3 of the License, or
7 (at your option) any later version.
8
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU General Public License for more details.
13
14 You should have received a copy of the GNU General Public License
15 along with this program. If not, see <https://www.gnu.org/licenses/>. */
16
17 #include <config.h>
18
19 /* Specification. */
20 #include <wchar.h>
21
22 /* Get iswprint. */
23 #include <wctype.h>
24
25 #include "localcharset.h"
26 #include "streq.h"
27 #include "uniwidth.h"
28
29 /* Returns 1 if the current locale is an UTF-8 locale, 0 otherwise. */
30 static inline int
is_locale_utf8(void)31 is_locale_utf8 (void)
32 {
33 const char *encoding = locale_charset ();
34 return STREQ_OPT (encoding, "UTF-8", 'U', 'T', 'F', '-', '8', 0, 0, 0, 0);
35 }
36
37 #if GNULIB_WCHAR_SINGLE_LOCALE
38 /* When we know that the locale does not change, provide a speedup by
39 caching the value of is_locale_utf8. */
40 static int cached_is_locale_utf8 = -1;
41 static inline int
is_locale_utf8_cached(void)42 is_locale_utf8_cached (void)
43 {
44 if (cached_is_locale_utf8 < 0)
45 cached_is_locale_utf8 = is_locale_utf8 ();
46 return cached_is_locale_utf8;
47 }
48 #else
49 /* By default, don't make assumptions, hence no caching. */
50 # define is_locale_utf8_cached is_locale_utf8
51 #endif
52
53 int
wcwidth(wchar_t wc)54 wcwidth (wchar_t wc)
55 #undef wcwidth
56 {
57 /* In UTF-8 locales, use a Unicode aware width function. */
58 if (is_locale_utf8_cached ())
59 {
60 /* We assume that in a UTF-8 locale, a wide character is the same as a
61 Unicode character. */
62 return uc_width (wc, "UTF-8");
63 }
64 else
65 {
66 /* Otherwise, fall back to the system's wcwidth function. */
67 #if HAVE_WCWIDTH
68 return wcwidth (wc);
69 #else
70 return wc == 0 ? 0 : iswprint (wc) ? 1 : -1;
71 #endif
72 }
73 }
74