1Locale::libintlFAQ(3) User Contributed Perl DocumentationLocale::libintlFAQ(3)
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6 Locale::TextDomain::FAQ - Frequently asked questions for libintl-perl
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9 This FAQ
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12 Why is libintl-perl so big? Why don't you use Encode(3pm) for character
13 set conversion instead of rolling your own version?
14 Encode(3pm) requires at least Perl 5.7.x, whereas libintl-perl needs to
15 be operational on Perl 5.004. Internally, libintl-perl uses
16 Encode(3pm) if it is available.
17 Why do the gettext functions always unset the utf-8 flag on the strings it
19 returns?
20 Because the gettext functions do not know whether the string is encoded
21 in utf-8 or not. Instead of taking guesses, it rather unsets the flag.
22 Can I set the utf-8 flag on strings returned by the gettext family of
24 functions?
25 Yes, but it is not recommended. If you absolutely want to do it, use
26 the function bind_textdomain_filter in Locale::Messages for it.
27 The strings returned by gettext and friends are by default encoded in
29 the preferred charset for the user's locale, but there is no portable
30 way to find out, whether this is utf-8 or not. That means, you either
31 have to enforce utf-8 as the output character set (by means of
32 bind_textdomain_codeset() and/or the environment variable
33 OUTPUT_CHARSET) and override the user preference, or you run the risk
34 of marking strings as utf-8 which really aren't utf-8.
35 The whole concept behind that utf-8 flag introduced in Perl 5.6 is
37 seriously broken, and the above described dilemma is a proof for that.
38 The best thing you can do with that flag is get rid of it, and turn it
39 off. Your code will benefit from it and become less error prone, more
40 portable and faster.
41 Why do non-ASCII characters in my Gtk2 application look messed up?
43 The Perl binding of Gtk2 has a design flaw. It expects all UI messages
44 to be in UTF-8 and it also expects messages to be flagged as utf-8.
45 The only solution for you is to enforce all your po files to be encoded
46 in utf-8 (convert them manually, if you need to), and also enforce that
47 charset in your application, regardless of the user's locale settings.
48 Assumed that your textdomain is "org.bar.foo", you have to code the
49 following into your main module or script:
50 BEGIN {
52 bind_textdomain_filter 'org.bar.foo', \&turn_utf_8_on;
53 bind_textdomain_codeset 'org.bar.foo', 'utf-8';
54 }
55 See the File GTestRunner.pm of Test::Unit::GTestRunner(3pm) for
57 details.
58 How do I interface Glade2 UI definitions with libintl-perl?
60 Gtk2::GladeXML(3pm) seems to ignore calls to bind_textdomain(). See
61 the File GTestRunner.pm of Test::Unit::GTestRunner(3pm) for a possible
62 solution.
63 Why does Locale::TextDomain use a double underscore? I am used to a single
65 underscore from C or other languages.
66 Function names that consist of exactly one non-alphanumerical character
67 make the function automatically global in Perl. Besides, in Perl 6 the
68 concatenation operator will be the underscore instead of the dot.
69 How do I switch languages or force a certain language independently from
71 user settings read from the environment?
72 The simple answer is:
73 use POSIX qw (setlocale LC_ALL);
75 my $language = 'fr';
77 my $country = 'FR';
78 my $charset = 'iso-8859-1';
79 setlocale LC_ALL, "${language}_$country.$charset";
81 Sadly enough, this will fail in many cases. The problem is that locale
83 identifiers are not standardized and are completely system-dependent.
84 Not only their overall format, but also other details like case-
85 sensitivity. Some systems are very forgiving about the system - for
86 example normalizing charset descriptions - others very strict. In
87 order to be reasonably platform independent, you should try a list of
88 possible locale identifiers for your desired settings. This is about
89 what I would try for achieving the above:
90 my @tries = qw (
92 fr_FR.iso-8859-1 fr_FR.iso8859-1 fr_FR.iso88591
93 fr_FR.ISO-8859-1 fr_FR.ISO8859-1 fr_FR.ISO88591
94 fr.iso-8859-1 fr.iso8859-1 fr.iso88591
95 fr.ISO-8859-1 fr.ISO8859-1 fr.ISO88591
96 fr_FR
97 French_France.iso-8859-1 French_France.iso8859-1 French_France.iso88591
98 French_France.ISO-8859-1 French_France.ISO8859-1 French_France.ISO88591
99 French.iso-8859-1 French.iso8859-1 French.iso88591
100 French.ISO-8859-1 French.ISO8859-1 French.ISO88591
101 );
102 foreach my $try (@tries) {
103 last if setlocale LC_ALL, $try;
104 }
105 Set Locale::Util(3pm) for functions that help you with this.
107 Alternatively, you can force a certain language by setting the
109 environment variables LANGUAGE, LANG and OUTPUT_CHARSET, but this is
110 only guaranteed to work, if you use the pure Perl implementation of
111 gettext (see the documentation for select_package() in
112 Locale::Messages(3pm)). You would do the above like this:
113 use Locale::Messages qw (nl_putenv);
115 # LANGUAGE is a colon separated list of languages.
117 nl_putenv("LANGUAGE=fr_FR");
118 # If LANGUAGE is set, LANG should be set to the primary language.
120 # This is not needed for gettext, but for other parts of the system
121 # it is.
122 nl_putenv("LANG=fr_FR");
123 # Force an output charset like this:
125 nl_putenv("OUTPUT_CHARSET=iso-8859-1");
126 setlocale (LC_MESSAGES, 'C');
128 These environment variables are GNU extensions, and they are also
130 honored by libintl-perl. Still, you should always try to set the
131 locale with setlocale for the catch-all category LC_ALL. If you miss
132 to do so, your program's output maybe cluttered, mixing languages and
133 charsets, if the system runs in a locale that is not compatible with
134 your own language settings.
135 Remember that these environment variables are not guaranteed to work,
137 if you use an XS version of gettext. In order to force usage of the
138 pure Perl implementation, do the following:
139 Locale::Messages->select_package ('gettext_pp');
141 If you think, this is brain-damaged, you are right, but I cannot help
143 you. Actually there should be a more flexible API than setlocale, but
144 at the time of this writing there isn't. Until then, the
145 recommentation goes like this:
146 1) Try setting LC_ALL with Locale::Util.
148 2) If that does not succeed, either give up or ...
149 3) Reset LC_MESSAGES to C/POSIX.
150 4) Switch to pure Perl for gettext.
151 5) Set the environment variables LANGUAGE, LANG,
152 and OUTPUT_CHARSET to your desired values.
153 What is the advantage of libintl-perl over Locale::Maketext?
155 Of course, I can only give my personal opinion as an answer.
156 Locale::Maketext claims to fix design flaws in gettext. These alleged
158 design flaws, however, boil down to one pathological case which always
159 has a workaround. But both programmers and translators pay this fix
160 with an unnecessarily complicated interface.
161 The paramount advantage of libintl-perl is that it uses an approved
163 technology and concept. Except for Java(tm) programs, this is the
164 state-of-the-art concept for localizing Un*x software. Programmers
165 that have already localized software in C, C++, C#, Python, PHP, or a
166 number of other languages will feel instantly at home, when localizing
167 software written in Perl with libintl-perl. The same holds true for
168 the translators, because the files they deal with have exactly the same
169 format as those for other programming languages. They can use the same
170 set of tools, and even the commands they have to execute are the same.
171 With libintl-perl refactoring of the software is painless, even if you
173 modify, add or delete translatable strings. The gettext tools are
174 powerful enough to reduce the effort of the translators to the bare
175 minimum. Maintaining the message catalogs of Locale::Maketext in
176 larger scale projects, is IMHO unfeasible.
177 Editing the message catalogs of Locale::Maketext - they are really Perl
179 modules - asks too much from most translators, unless they are
180 programmers. The portable object (po) files used by libintl-perl have
181 a simple syntax, and there are a bunch of specialized GUI editors for
182 these files, that facilitate the translation process and hide most
183 complexity from the user.
184 Furthermore, libintl-perl makes it possible to mix programming
186 languages without a paradigm shift in localization. Without any
187 special efforts, you can write a localized software that has modules
188 written in C, modules in Perl, and builds a Gtk user interface with
189 Glade. All translatable strings end up in one single message catalog.
190 Last but not least, the interface used by libintl-perl is plain simple:
192 Prepend translatable strings with a double underscore, and you are done
193 in most cases.
194 Why do single-quoted strings not work?
196 You probably write something like this:
197 print __'Hello';
199 And you get an error message like "Can't find string terminator "'"
201 anywhere before EOF at ...", or even "Bareword found where operator
202 expected at ... Might be a runaway multi-line '' string starting on".
203 The above line is (really!) essentially the same as writing:
204 print __::Hello';
206 A lesser know feature of Perl is that you can use a single quote ("'")
208 as the separator in packages instead of the double colon (":"). What
209 the Perl parser sees in the first example is a valid package name
210 ("__") followed by the separator ("'"), then another valid package name
211 ("Hello") followed by a lone single quote. It is therefore not a
212 problem in libintl-perl but simple wrong Perl syntax. You have to
213 correct alternatives:
214 print __ 'Hello'; # Insert a space to disambiguate.
216 Or use double-quotes:
218 print __"Hello";
220 Thanks to Slavi Agafonkin for pointing me to the solution of this
222 mystery.
223 What options should be used with xgettext?
225 More precise, the question should be which '--keyword' and '--flag'
226 options for xgettext should be used. All other options are completely
227 dependent on your use-case.
228 If you are using Locale::Messages or Locale::Gettext for localizing
230 Perl code, the default keywords and default flags built into xgettext
231 are correct.
232 If you are using Locale::TextDomain you have to use a long plethora of
234 command-line options for xgettext. Beginning with libintl-perl 1.28
235 you can use the library itself to produce these options:
236 perl -MLocale::TextDomain -e 'print Locale::TextDomain->options'
238 If you want to disable the use of the built-in default keywords,
240 precede the output of the above command with '--keyword=""'. That will
241 reset the keywords for xgettext.
242 Why Isn't There A Function N__x(), N__nx(), or N__px()?
244 The sole purpose of these functions would be to set proper flags in the
245 output of xgettext(1). You probably thought of something like this:
246 xgettext --keyword=N__x --flag=N__x:1:perl-brace-format filename.pl
248 First of all, xgettext(1) will always set the flag correctly if the
250 argument to N__() looks like a brace format string.
251 Second, you can set any flag you want on the PO entry with a source
253 code comment:
254 # xgettext: no-perl-brace-format
256 my $msg = N__("Placeholders are enclosed in {curly} braces.");
257 When xgettext(1) extracts the string, it will appear like this in the
259 .pot file:
260 #: filename.pl:2304
262 #, no-perl-brace-format
263 msgid "Placeholders are enclosed in {curly} braces."
264 msgstr ""
265 No reason to pollute the namespace with N__x functions.
267perl v5.28.0 2018-07-15 Locale::libintlFAQ(3)