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 1.4.2
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::mcunknown locale src-string
30_________________________________________________________________
31
33 The msgcat package provides a set of functions that can be used to man‐
34 age multi-lingual user interfaces. Text strings are defined in a “mes‐
35 sage catalog” which is independent from the application, and which can
36 be edited or localized without modifying the application source code.
37 New languages or locales are provided by adding a new file to the mes‐
38 sage catalog.
39 Use of the message catalog is optional by any application or package,
41 but is encouraged if the application or package wishes to be enabled
42 for multi-lingual applications.
43
45 ::msgcat::mc src-string ?arg arg ...?
46 Returns a translation of src-string according to the user's cur‐
47 rent locale. If additional arguments past src-string are given,
48 the format command is used to substitute the additional argu‐
49 ments in the translation of src-string.
50 ::msgcat::mc will search the messages defined in the current
52 namespace for a translation of src-string; if none is found, it
53 will search in the parent of the current namespace, and so on
54 until it reaches the global namespace. If no translation string
55 exists, ::msgcat::mcunknown is called and the string returned
56 from ::msgcat::mcunknown is returned.
57 ::msgcat::mc is the main function used to localize an applica‐
59 tion. Instead of using an English string directly, an applica‐
60 tion can pass the English string through ::msgcat::mc and use
61 the result. If an application is written for a single language
62 in this fashion, then it is easy to add support for additional
63 languages later simply by defining new message catalog entries.
64 ::msgcat::mcmax ?src-string src-string ...?
66 Given several source strings, ::msgcat::mcmax returns the length
67 of the longest translated string. This is useful when designing
68 localized GUIs, which may require that all buttons, for example,
69 be a fixed width (which will be the width of the widest button).
70 ::msgcat::mclocale ?newLocale?
72 This function sets the locale to newLocale. If newLocale is
73 omitted, the current locale is returned, otherwise the current
74 locale is set to newLocale. msgcat stores and compares the
75 locale in a case-insensitive manner, and returns locales in low‐
76 ercase. The initial locale is determined by the locale speci‐
77 fied in the user's environment. See LOCALE SPECIFICATION below
78 for a description of the locale string format.
79 ::msgcat::mcpreferences
81 Returns an ordered list of the locales preferred by the user,
82 based on the user's language specification. The list is ordered
83 from most specific to least preference. The list is derived
84 from the current locale set in msgcat by ::msgcat::mclocale, and
85 cannot be set independently. For example, if the current locale
86 is en_US_funky, then ::msgcat::mcpreferences returns │
87 {en_US_funky en_US en {}}.
88 ::msgcat::mcload dirname
90 Searches the specified directory for files that match the lan‐
91 guage specifications returned by ::msgcat::mcpreferences (note
92 that these are all lowercase), extended by the file extension
93 “.msg”. Each matching file is read in order, assuming a UTF-8
94 encoding. The file contents are then evaluated as a Tcl script.
95 This means that Unicode characters may be present in the message
96 file either directly in their UTF-8 encoded form, or by use of
97 the backslash-u quoting recognized by Tcl evaluation. The num‐
98 ber of message files which matched the specification and were
99 loaded is returned.
100 ::msgcat::mcset locale src-string ?translate-string?
102 Sets the translation for src-string to translate-string in the
103 specified locale and the current namespace. If translate-string
104 is not specified, src-string is used for both. The function
105 returns translate-string.
106 ::msgcat::mcmset locale src-trans-list
108 Sets the translation for multiple source strings in src-trans-
109 list in the specified locale and the current namespace. src-
110 trans-list must have an even number of elements and is in the
111 form {src-string translate-string ?src-string translate-string
112 ...?} ::msgcat::mcmset can be significantly faster than multiple
113 invocations of ::msgcat::mcset. The function returns the number
114 of translations set.
115 ::msgcat::mcunknown locale src-string
117 This routine is called by ::msgcat::mc in the case when a trans‐
118 lation for src-string is not defined in the current locale. The
119 default action is to return src-string. This procedure can be
120 redefined by the application, for example to log error messages
121 for each unknown string. The ::msgcat::mcunknown procedure is
122 invoked at the same stack context as the call to ::msgcat::mc.
123 The return value of ::msgcat::mcunknown is used as the return
124 value for the call to ::msgcat::mc.
125
127 The locale is specified to msgcat by a locale string passed to ::msg‐
128 cat::mclocale. The locale string consists of a language code, an
129 optional country code, and an optional system-specific code, each sepa‐
130 rated by “_”. The country and language codes are specified in stan‐
131 dards ISO-639 and ISO-3166. For example, the locale “en” specifies
132 English and “en_US” specifies U.S. English.
133 When the msgcat package is first loaded, the locale is initialized
135 according to the user's environment. The variables env(LC_ALL),
136 env(LC_MESSAGES), and env(LANG) are examined in order. The first of
137 them to have a non-empty value is used to determine the initial locale.
138 The value is parsed according to the XPG4 pattern
139 language[_country][.codeset][@modifier]
140 to extract its parts. The initial locale is then set by calling ::msg‐
141 cat::mclocale with the argument
142 language[_country][_modifier]
143 On Windows, if none of those environment variables is set, msgcat will
144 attempt to extract locale information from the registry. If all these
145 attempts to discover an initial locale from the user's environment
146 fail, msgcat defaults to an initial locale of “C”.
147 When a locale is specified by the user, a “best match” search is per‐
149 formed during string translation. For example, if a user specifies │
150 en_GB_Funky, the locales “en_GB_Funky”, “en_GB”, “en” and (the empty │
151 string) are searched in order until a matching translation string is
152 found. If no translation string is available, then ::msgcat::mcunknown
153 is called.
154
156 Strings stored in the message catalog are stored relative to the
157 namespace from which they were added. This allows multiple packages to
158 use the same strings without fear of collisions with other packages.
159 It also allows the source string to be shorter and less prone to
160 typographical error.
161 For example, executing the code
163 ::msgcat::mcset en hello "hello from ::"
164 namespace eval foo {
165 ::msgcat::mcset en hello "hello from ::foo"
166 }
167 puts [::msgcat::mc hello]
168 namespace eval foo {puts [::msgcat::mc hello]}
169 will print
170 hello from ::
171 hello from ::foo
172 When searching for a translation of a message, the message catalog will
174 search first the current namespace, then the parent of the current
175 namespace, and so on until the global namespace is reached. This
176 allows child namespaces to “inherit” messages from their parent
177 namespace.
178 For example, executing (in the “en” locale) the code
180 ::msgcat::mcset en m1 ":: message1"
181 ::msgcat::mcset en m2 ":: message2"
182 ::msgcat::mcset en m3 ":: message3"
183 namespace eval ::foo {
184 ::msgcat::mcset en m2 "::foo message2"
185 ::msgcat::mcset en m3 "::foo message3"
186 }
187 namespace eval ::foo::bar {
188 ::msgcat::mcset en m3 "::foo::bar message3"
189 }
190 namespace import ::msgcat::mc
191 puts "[mc m1]; [mc m2]; [mc m3]"
192 namespace eval ::foo {puts "[mc m1]; [mc m2]; [mc m3]"}
193 namespace eval ::foo::bar {puts "[mc m1]; [mc m2]; [mc m3]"}
194 will print
195 :: message1; :: message2; :: message3
196 :: message1; ::foo message2; ::foo message3
197 :: message1; ::foo message2; ::foo::bar message3
198
200 Message files can be located in any directory, subject to the following
201 conditions:
202 [1] All message files for a package are in the same directory.
204 [2] The message file name is a msgcat locale specifier (all
206 lowercase) followed by “.msg”. For example:
207 es.msg — spanish
208 en_gb.msg — United Kingdom English
209 Exception: The message file for the root locale is called “ROOT.msg”. │
210 This exception is made so as not to cause peculiar behavior, such as │
211 marking the message file as “hidden” on Unix file systems.
212 [3] The file contains a series of calls to mcset and mcmset, setting
214 the necessary translation strings for the language, likely
215 enclosed in a namespace eval so that all source strings are tied
216 to the namespace of the package. For example, a short es.msg
217 might contain:
218 namespace eval ::mypackage {
219 ::msgcat::mcset es "Free Beer!" "Cerveza Gracias!"
220 }
221
223 If a package is installed into a subdirectory of the tcl_pkgPath and
224 loaded via package require, the following procedure is recommended.
225 [1] During package installation, create a subdirectory msgs under
227 your package directory.
228 [2] Copy your *.msg files into that directory.
230 [3]
232 Add the following command to your package initialization
233 script:
234 # load language files, stored in msgs subdirectory
235 ::msgcat::mcload [file join [file dirname [info script]] msgs]
236
238 It is possible that a message string used as an argument to format
239 might have positionally dependent parameters that might need to be
240 repositioned. For example, it might be syntactically desirable to
241 rearrange the sentence structure while translating.
242 format "We produced %d units in location %s" $num $city
243 format "In location %s we produced %d units" $city $num
244 This can be handled by using the positional parameters:
246 format "We produced %1\$d units in location %2\$s" $num $city
247 format "In location %2\$s we produced %1\$d units" $num $city
248 Similarly, positional parameters can be used with scan to extract
250 values from internationalized strings.
251
253 The message catalog code was developed by Mark Harrison.
254
256 format(n), scan(n), namespace(n), package(n)
257
259 internationalization, i18n, localization, l10n, message, text,
260 translation
261msgcat 1.4 msgcat(n)