msgcat(1,n)(n) Tcl Bundled Packages msgcat(1,n)(n) NAME msgcat(1,n) - Tcl message catalog SYNOPSIS package require Tcl 8.2 package require msgcat(1,n) 1.3 ::msgcat::mc src-string ?arg arg ...? ::msgcat::mcmax ?src-string src-string ...? ::msgcat::mclocale ?newLocale? ::msgcat::mcpreferences ::msgcat::mcload dirname ::msgcat::mcset locale(3,5,7) src-string ?translate-string? ::msgcat::mcmset locale(3,5,7) src-trans-list ::msgcat::mcunknown locale(3,5,7) src-string DESCRIPTION The msgcat(1,n) package provides a set(7,n,1 builtins) of functions that can be used to man- age multi-lingual user interfaces. Text strings are defined in(1,8) a ``message catalog'' which is independent from the application, and which can be edited or localized without modifying the application source code. New languages or locales are provided by adding a new file(1,n) to the message catalog. Use of the message catalog is optional by any application or package, but is encouraged if(3,n) the application or package wishes to be enabled for multi-lingual applications. COMMANDS ::msgcat::mc src-string ?arg arg ...? Returns a translation of src-string according to the user's cur- rent locale. If additional arguments past src-string are given, the format command is used to substitute the additional argu- ments in(1,8) the translation of src-string. ::msgcat::mc will search the messages defined in(1,8) the current namespace for a translation of src-string; if(3,n) none is found, it will search in(1,8) the parent of the current namespace, and so on until it reaches the global namespace. If no translation string(3,n) exists, ::msgcat::mcunknown is called and the string(3,n) returned from ::msgcat::mcunknown is returned. ::msgcat::mc is the main function used to localize an application. Instead of using an English string(3,n) directly, an application can pass the English string(3,n) through ::msgcat::mc and use the result. If an application is written for a single language in(1,8) this fashion, then it is easy to add support for additional languages later simply by defin- ing new message catalog entries. ::msgcat::mcmax ?src-string src-string ...? Given several source strings, ::msgcat::mcmax returns the length of the longest translated string. This is useful when designing localized GUIs, which may require that all buttons, for example, be a fixed width (which will be the width of the widest button). ::msgcat::mclocale ?newLocale? This function sets the locale(3,5,7) to newLocale. If newLocale is omitted, the current locale(3,5,7) is returned, otherwise the current locale(3,5,7) is set(7,n,1 builtins) to newLocale. msgcat(1,n) stores and compares the locale(3,5,7) in(1,8) a case-insensitive manner, and returns locales in(1,8) low- ercase. The initial locale(3,5,7) is determined by the locale(3,5,7) speci- fied in(1,8) the user's environment. See LOCALE SPECIFICATION below for a description of the locale(3,5,7) string(3,n) format. ::msgcat::mcpreferences Returns an ordered list of the locales preferred by the user, based on the user's language specification. The list is ordered from most specific to least preference. The list is derived from the current locale(3,5,7) set(7,n,1 builtins) in(1,8) msgcat(1,n) by msgcat::mclocale, and cannot be set(7,n,1 builtins) independently. For example, if(3,n) the current locale(3,5,7) is en_US_funky, then msgcat::mcpreferences returns {en_US_funky en_US en}. ::msgcat::mcload dirname Searches the specified directory for files that match the lan- guage specifications returned by ::msgcat::mcpreferences (note that these are all lowercase), extended by the file(1,n) extension ``.msg''. Each matching file(1,n) is read(2,n,1 builtins) in(1,8) order, assuming a UTF-8 encoding. The file(1,n) contents are then evaluated as a Tcl script. This means that non-Latin characters may be present in(1,8) the mes- sage file(1,n) either directly in(1,8) their UTF-8 encoded form, or by use of the backslash-u quoting recognized by Tcl evaluation. The number of message files which matched the specification and were loaded is returned. ::msgcat::mcset locale(3,5,7) src-string ?translate-string? Sets the translation for src-string to translate-string in(1,8) the specified locale(3,5,7) and the current namespace. If translate-string is not specified, src-string is used for both. The function returns translate-string. ::msgcat::mcmset locale(3,5,7) src-trans-list Sets the translation for multiple source strings in(1,8) src-trans- list in(1,8) the specified locale(3,5,7) and the current namespace. src- trans-list must have an even number of elements and is in(1,8) the form {src-string translate-string ?src-string translate-string ...?} msgcat::mcmset can be significantly faster than multiple invocations of msgcat::mcset. The function returns the number of translations set. ::msgcat::mcunknown locale(3,5,7) src-string This routine is called by ::msgcat::mc in(1,8) the case when a trans- lation for src-string is not defined in(1,8) the current locale. The default action is to return src-string. This procedure can be redefined by the application, for example to log error(8,n) messages for each unknown string. The ::msgcat::mcunknown procedure is invoked at the same stack context as the call to ::msgcat::mc. The return value of ::msgcat::mcunknown is used as the return value for the call to ::msgcat::mc. LOCALE SPECIFICATION The locale(3,5,7) is specified to msgcat(1,n) by a locale(3,5,7) string(3,n) passed to ::msg- cat::mclocale. The locale(3,5,7) string(3,n) consists of a language code, an optional country code, and an optional system-specific code, each sepa- rated by ``_''. The country and language codes are specified in(1,8) stan- dards ISO-639 and ISO-3166. For example, the locale(3,5,7) ``en'' specifies English and ``en_US'' specifies U.S. English. When the msgcat(1,n) package is first loaded, the locale(3,5,7) is initialized according to the user's environment. The variables env(1,3)(LC_ALL), env(1,3)(LC_MESSAGES), and env(1,3)(LANG) are examined in(1,8) order. The first of them to have a non-empty value is used to determine the initial locale. The value is parsed according to the XPG4 pattern language[_coun- try][.codeset][@modifier] to extract its parts. The initial locale(3,5,7) is then set(7,n,1 builtins) by calling msgcat::mclocale with the argument language[_coun- try][_modifier] On Windows, if(3,n) none of those environment variables is set(7,n,1 builtins), msgcat(1,n) will attempt to extract locale(3,5,7) information from the reg- istry. If all these attempts to discover(1,3,5) an initial locale(3,5,7) from the user's environment fail, msgcat(1,n) defaults to an initial locale(3,5,7) of ``C''. When a locale(3,5,7) is specified by the user, a ``best match'' search is per- formed during string(3,n) translation. For example, if(3,n) a user specifies en_GB_Funky, the locales ``en_GB_Funky'', ``en_GB'', and ``en'' are searched in(1,8) order until a matching translation string(3,n) is found. If no translation string(3,n) is available, then ::msgcat::unknown is called. NAMESPACES AND MESSAGE CATALOGS Strings stored in(1,8) the message catalog are stored relative to the names- pace from which they were added. This allows multiple packages to use the same strings without fear of collisions with other packages. It also allows the source string(3,n) to be shorter and less(1,3) prone to typo- graphical error. For example, executing the code mcset en hello "hello from ::" names- pace eval foo {mcset en hello "hello from ::foo"} puts(3,n) [mc hello] namespace eval foo {puts(3,n) [mc hello]} will print hello from :: hello from ::foo When searching for a translation of a message, the message catalog will search first the current namespace, then the parent of the current namespace, and so on until the global namespace is reached. This allows child namespaces to "inherit" messages from their parent names- pace. For example, executing (in(1,8) the ``en'' locale(3,5,7)) the code mcset en m1 ":: message1" mcset en m2 ":: message2" mcset en m3 ":: message3" namespace eval ::foo { mcset en m2 "::foo message2" mcset en m3 "::foo message3" } namespace eval ::foo::bar { mcset en m3 "::foo::bar message3" } puts(3,n) "[mc m1]; [mc m2]; [mc m3]" namespace eval ::foo {puts(3,n) "[mc m1]; [mc m2]; [mc m3]"} namespace eval ::foo::bar {puts(3,n) "[mc m1]; [mc m2]; [mc m3]"} will print :: mes- sage1; :: message2; :: message3 :: message1; ::foo message2; ::foo mes- sage3 :: message1; ::foo message2; ::foo::bar message3 LOCATION AND FORMAT OF MESSAGE FILES Message files can be located in(1,8) any directory, subject to the following conditions: [1] All message files for a package are in(1,8) the same directory. [2] The message file(1,n) name is a msgcat(1,n) locale(3,5,7) specifier (all lower- case) followed by ``.msg''. For example: es.msg -- spanish en_gb.msg -- United Kingdom English [3] The file(1,n) contains a series of calls to mcset and mcmset, setting the necessary translation strings for the language, likely enclosed in(1,8) a namespace eval so that all source strings are tied to the namespace of the package. For example, a short es.msg might contain: namespace eval ::mypackage { ::msgcat::mcset es "Free Beer!" "Cerveza Gracias!" } RECOMMENDED MESSAGE SETUP FOR PACKAGES If a package is installed into a subdirectory of the tcl_pkgPath and loaded via package require, the following procedure is recommended. [1] During package installation, create a subdirectory msgs under your package directory. [2] Copy your *.msg files into that directory. [3] Add the following command to your package initialization script: # load(7,n) language files, stored in(1,8) msgs subdirectory ::msgcat::mcload [file(1,n) join(1,n) [file(1,n) dirname [info(1,5,n) script]] msgs] POSITIONAL CODES FOR FORMAT AND SCAN COMMANDS It is possible that a message string(3,n) used as an argument to format might have positionally dependent parameters that might need to be repositioned. For example, it might be syntactically desirable to rearrange the sentence structure while translating. format "We pro- duced %d units(1,7) in(1,8) location %s" $num $city format "In location %s we produced %d units(1,7)" $city $num This can be handled by using the positional parameters: format "We pro- duced %1\$d units(1,7) in(1,8) location %2\$s" $num $city format "In location %2\$s we produced %1\$d units(1,7)" $num $city Similarly, positional parameters can be used with scan to extract val- ues from internationalized strings. CREDITS The message catalog code was developed by Mark Harrison. SEE ALSO format(n), scan(n), namespace(n), package(n) KEYWORDS internationalization, i18n, localization, l10n, message, text, transla- tion msgcat(1,n) 1.3 msgcat(1,n)(n)