1msgcat(n) Tcl Bundled Packages msgcat(n)
2______________________________________________________________________________
6
8 msgcat - Tcl message catalog
9
11 package require Tcl 8.5
12 package require msgcat 1.5.0
14 ::msgcat::mc src-string ?arg arg ...?
16 ::msgcat::mcmax ?src-string src-string ...?
18 ::msgcat::mclocale ?newLocale?
20 ::msgcat::mcpreferences
22 ::msgcat::mcload dirname
24 ::msgcat::mcset locale src-string ?translate-string?
26 ::msgcat::mcmset locale src-trans-list
28 ::msgcat::mcflset src-string ?translate-string? │
30 ::msgcat::mcflmset src-trans-list
32 ::msgcat::mcunknown locale src-string
34_________________________________________________________________
35
37 The msgcat package provides a set of functions that can be used to man‐
38 age multi-lingual user interfaces. Text strings are defined in a “mes‐
39 sage catalog” which is independent from the application, and which can
40 be edited or localized without modifying the application source code.
41 New languages or locales are provided by adding a new file to the mes‐
42 sage catalog.
43 Use of the message catalog is optional by any application or package,
45 but is encouraged if the application or package wishes to be enabled
46 for multi-lingual applications.
47
49 ::msgcat::mc src-string ?arg arg ...?
50 Returns a translation of src-string according to the user's cur‐
51 rent locale. If additional arguments past src-string are given,
52 the format command is used to substitute the additional argu‐
53 ments in the translation of src-string.
54 ::msgcat::mc will search the messages defined in the current
56 namespace for a translation of src-string; if none is found, it
57 will search in the parent of the current namespace, and so on
58 until it reaches the global namespace. If no translation string
59 exists, ::msgcat::mcunknown is called and the string returned
60 from ::msgcat::mcunknown is returned.
61 ::msgcat::mc is the main function used to localize an applica‐
63 tion. Instead of using an English string directly, an applica‐
64 tion can pass the English string through ::msgcat::mc and use
65 the result. If an application is written for a single language
66 in this fashion, then it is easy to add support for additional
67 languages later simply by defining new message catalog entries.
68 ::msgcat::mcmax ?src-string src-string ...?
70 Given several source strings, ::msgcat::mcmax returns the length
71 of the longest translated string. This is useful when designing
72 localized GUIs, which may require that all buttons, for example,
73 be a fixed width (which will be the width of the widest button).
74 ::msgcat::mclocale ?newLocale?
76 This function sets the locale to newLocale. If newLocale is
77 omitted, the current locale is returned, otherwise the current
78 locale is set to newLocale. msgcat stores and compares the
79 locale in a case-insensitive manner, and returns locales in low‐
80 ercase. The initial locale is determined by the locale speci‐
81 fied in the user's environment. See LOCALE SPECIFICATION below
82 for a description of the locale string format.
83 ::msgcat::mcpreferences
85 Returns an ordered list of the locales preferred by the user,
86 based on the user's language specification. The list is ordered
87 from most specific to least preference. The list is derived
88 from the current locale set in msgcat by ::msgcat::mclocale, and
89 cannot be set independently. For example, if the current locale
90 is en_US_funky, then ::msgcat::mcpreferences returns
91 {en_US_funky en_US en {}}.
92 ::msgcat::mcload dirname
94 Searches the specified directory for files that match the lan‐
95 guage specifications returned by ::msgcat::mcpreferences (note
96 that these are all lowercase), extended by the file extension
97 “.msg”. Each matching file is read in order, assuming a UTF-8
98 encoding. The file contents are then evaluated as a Tcl script.
99 This means that Unicode characters may be present in the message
100 file either directly in their UTF-8 encoded form, or by use of
101 the backslash-u quoting recognized by Tcl evaluation. The num‐
102 ber of message files which matched the specification and were
103 loaded is returned.
104 ::msgcat::mcset locale src-string ?translate-string?
106 Sets the translation for src-string to translate-string in the
107 specified locale and the current namespace. If translate-string
108 is not specified, src-string is used for both. The function
109 returns translate-string.
110 ::msgcat::mcmset locale src-trans-list
112 Sets the translation for multiple source strings in src-trans-
113 list in the specified locale and the current namespace. src-
114 trans-list must have an even number of elements and is in the
115 form {src-string translate-string ?src-string translate-string
116 ...?} ::msgcat::mcmset can be significantly faster than multiple
117 invocations of ::msgcat::mcset. The function returns the number
118 of translations set.
119 ::msgcat::mcflset src-string ?translate-string?
121 Sets the translation for src-string to translate-string in the │
122 current namespace for the locale implied by the name of the mes‐ │
123 sage catalog being loaded via ::msgcat::mcload. If translate- │
124 string is not specified, src-string is used for both. The func‐ │
125 tion returns translate-string.
126 ::msgcat::mcflmset src-trans-list
128 Sets the translation for multiple source strings in src-trans- │
129 list in the current namespace for the locale implied by the name │
130 of the message catalog being loaded via ::msgcat::mcload. src- │
131 trans-list must have an even number of elements and is in the │
132 form {src-string translate-string ?src-string translate-string │
133 ...?} ::msgcat::mcflmset can be significantly faster than multi‐ │
134 ple invocations of ::msgcat::mcflset. The function returns the │
135 number of translations set.
136 ::msgcat::mcunknown locale src-string
138 This routine is called by ::msgcat::mc in the case when a trans‐
139 lation for src-string is not defined in the current locale. The
140 default action is to return src-string. This procedure can be
141 redefined by the application, for example to log error messages
142 for each unknown string. The ::msgcat::mcunknown procedure is
143 invoked at the same stack context as the call to ::msgcat::mc.
144 The return value of ::msgcat::mcunknown is used as the return
145 value for the call to ::msgcat::mc.
146
148 The locale is specified to msgcat by a locale string passed to ::msg‐
149 cat::mclocale. The locale string consists of a language code, an
150 optional country code, and an optional system-specific code, each sepa‐
151 rated by “_”. The country and language codes are specified in stan‐
152 dards ISO-639 and ISO-3166. For example, the locale “en” specifies
153 English and “en_US” specifies U.S. English.
154 When the msgcat package is first loaded, the locale is initialized
156 according to the user's environment. The variables env(LC_ALL),
157 env(LC_MESSAGES), and env(LANG) are examined in order. The first of
158 them to have a non-empty value is used to determine the initial locale.
159 The value is parsed according to the XPG4 pattern
160 language[_country][.codeset][@modifier]
162 to extract its parts. The initial locale is then set by calling ::msg‐
164 cat::mclocale with the argument
165 language[_country][_modifier]
167 On Windows and Cygwin, if none of those environment variables is set,
169 msgcat will attempt to extract locale information from the registry.
170 From Windows Vista on, the RFC4747 locale name "lang-script-country-
171 options" is transformed to the locale as "lang_country_script" (Exam‐
172 ple: sr-Latn-CS -> sr_cs_latin). For Windows XP, the language id is
173 transformed analoguously (Example: 0c1a -> sr_yu_cyrillic). If all
174 these attempts to discover an initial locale from the user's environ‐
175 ment fail, msgcat defaults to an initial locale of “C”.
176 When a locale is specified by the user, a “best match” search is per‐
178 formed during string translation. For example, if a user specifies
179 en_GB_Funky, the locales “en_GB_Funky”, “en_GB”, “en” and (the empty
180 string) are searched in order until a matching translation string is
181 found. If no translation string is available, then ::msgcat::mcunknown
182 is called.
183
185 Strings stored in the message catalog are stored relative to the
186 namespace from which they were added. This allows multiple packages to
187 use the same strings without fear of collisions with other packages.
188 It also allows the source string to be shorter and less prone to
189 typographical error.
190 For example, executing the code
192 ::msgcat::mcset en hello "hello from ::"
194 namespace eval foo {
195 ::msgcat::mcset en hello "hello from ::foo"
196 }
197 puts [::msgcat::mc hello]
198 namespace eval foo {puts [::msgcat::mc hello]}
199 will print
201 hello from ::
203 hello from ::foo
204 When searching for a translation of a message, the message catalog will
206 search first the current namespace, then the parent of the current
207 namespace, and so on until the global namespace is reached. This
208 allows child namespaces to “inherit” messages from their parent
209 namespace.
210 For example, executing (in the “en” locale) the code
212 ::msgcat::mcset en m1 ":: message1"
214 ::msgcat::mcset en m2 ":: message2"
215 ::msgcat::mcset en m3 ":: message3"
216 namespace eval ::foo {
217 ::msgcat::mcset en m2 "::foo message2"
218 ::msgcat::mcset en m3 "::foo message3"
219 }
220 namespace eval ::foo::bar {
221 ::msgcat::mcset en m3 "::foo::bar message3"
222 }
223 namespace import ::msgcat::mc
224 puts "[mc m1]; [mc m2]; [mc m3]"
225 namespace eval ::foo {puts "[mc m1]; [mc m2]; [mc m3]"}
226 namespace eval ::foo::bar {puts "[mc m1]; [mc m2]; [mc m3]"}
227 will print
229 :: message1; :: message2; :: message3
231 :: message1; ::foo message2; ::foo message3
232 :: message1; ::foo message2; ::foo::bar message3
233
235 Message files can be located in any directory, subject to the following
236 conditions:
237 [1] All message files for a package are in the same directory.
239 [2] The message file name is a msgcat locale specifier (all
241 lowercase) followed by “.msg”. For example:
242 es.msg — spanish
244 en_gb.msg — United Kingdom English
245 Exception: The message file for the root locale is called “ROOT.msg”.
247 This exception is made so as not to cause peculiar behavior, such as
248 marking the message file as “hidden” on Unix file systems.
249 [3] The file contains a series of calls to mcflset and mcflmset,
251 setting the necessary translation strings for the language,
252 likely enclosed in a namespace eval so that all source strings
253 are tied to the namespace of the package. For example, a short
254 es.msg might contain:
255 namespace eval ::mypackage {
257 ::msgcat::mcflset "Free Beer!" "Cerveza Gracias!"
258 }
259
261 If a package is installed into a subdirectory of the tcl_pkgPath and
262 loaded via package require, the following procedure is recommended.
263 [1] During package installation, create a subdirectory msgs under
265 your package directory.
266 [2] Copy your *.msg files into that directory.
268 [3] Add the following command to your package initialization script:
270 # load language files, stored in msgs subdirectory
272 ::msgcat::mcload [file join [file dirname [info script]] msgs]
273
275 It is possible that a message string used as an argument to format
276 might have positionally dependent parameters that might need to be
277 repositioned. For example, it might be syntactically desirable to
278 rearrange the sentence structure while translating.
279 format "We produced %d units in location %s" $num $city
281 format "In location %s we produced %d units" $city $num
282 This can be handled by using the positional parameters:
284 format "We produced %1\$d units in location %2\$s" $num $city
286 format "In location %2\$s we produced %1\$d units" $num $city
287 Similarly, positional parameters can be used with scan to extract
289 values from internationalized strings. Note that it is not necessary to
290 pass the output of ::msgcat::mc to format directly; by passing the
291 values to substitute in as arguments, the formatting substitution is
292 done directly.
293 msgcat::mc {Produced %1$d at %2$s} $num $city
295 # ... where that key is mapped to one of the
296 # human-oriented versions by msgcat::mcset
297
299 The message catalog code was developed by Mark Harrison.
300
302 format(n), scan(n), namespace(n), package(n)
303
305 internationalization, i18n, localization, l10n, message, text,
306 translation
307msgcat 1.5 msgcat(n)