msgcat(n) Tcl Bundled Packages msgcat(n) 







msgcat - Tcl message catalog








package require Tcl 8.5


package require msgcat 1.4.2


::msgcat::mc src-string ?arg arg ...?


::msgcat::mcmax ?src-string src-string ...?


::msgcat::mclocale ?newLocale?


::msgcat::mcpreferences


::msgcat::mcload dirname


::msgcat::mcset locale src-string
    ?translate-string?


::msgcat::mcmset locale src-trans-list


::msgcat::mcunknown locale src-string










The msgcat package provides a set of functions that can be
    used to manage multi-lingual user interfaces. Text strings are defined in 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 to
    the message catalog.


Use of the message catalog is optional by any application or
    package, but is encouraged if the application or package wishes to be
    enabled for multi-lingual applications.









  
::msgcat::mc src-string ?arg arg ...?

  
Returns a translation of src-string according to the user's current
      locale. If additional arguments past src-string are given, the
      format command is used to substitute the additional arguments in
      the translation of src-string.






::msgcat::mc will search the messages defined in the
    current namespace for a translation of src-string; if none is found,
    it will search in the parent of the current namespace, and so on until it
    reaches the global namespace. If no translation string exists,
    ::msgcat::mcunknown is called and the string returned from
    ::msgcat::mcunknown is returned.


::msgcat::mc is the main function used to localize an
    application. Instead of using an English string directly, an application can
    pass the English string through ::msgcat::mc and use the result. If
    an application is written for a single language in this fashion, then it is
    easy to add support for additional languages later simply by defining 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 to newLocale. If newLocale is
      omitted, the current locale is returned, otherwise the current locale is
      set to newLocale. msgcat stores and compares the locale in a
      case-insensitive manner, and returns locales in lowercase. The initial
      locale is determined by the locale specified in the user's environment.
      See LOCALE SPECIFICATION below for a description of the locale
      string 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 set in
      msgcat by ::msgcat::mclocale, and cannot be set independently. For
      example, if the current locale 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 language
      specifications returned by ::msgcat::mcpreferences (note that these
      are all lowercase), extended by the file extension “.msg”.
      Each matching file is read in order, assuming a UTF-8 encoding. The file
      contents are then evaluated as a Tcl script. This means that Unicode
      characters may be present in the message file either directly in 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 src-string
    ?translate-string?

  
Sets the translation for src-string to translate-string in
      the specified locale and the current namespace. If
      translate-string is not specified, src-string is used for
      both. The function returns translate-string.

  
::msgcat::mcmset locale src-trans-list

  
Sets the translation for multiple source strings in src-trans-list
      in the specified locale and the current namespace.
      src-trans-list must have an even number of elements and is in 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 src-string

  
This routine is called by ::msgcat::mc in the case when a
      translation for src-string is not defined in the current locale.
      The default action is to return src-string. This procedure can be
      redefined by the application, for example to log error 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.










The locale is specified to msgcat by a locale string passed
    to ::msgcat::mclocale. The locale string consists of a language code,
    an optional country code, and an optional system-specific code, each
    separated by “_”. The country and language codes are specified
    in standards ISO-639 and ISO-3166. For example, the locale
    “en” specifies English and “en_US” specifies
    U.S. English.


When the msgcat package is first loaded, the locale is initialized
    according to the user's environment. The variables env(LC_ALL),
    env(LC_MESSAGES), and env(LANG) are examined in 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[_country][.codeset][@modifier]



to extract its parts. The initial locale is then set by calling
  ::msgcat::mclocale with the argument



language[_country][_modifier]



On Windows, if none of those environment variables is set, msgcat will attempt
  to extract locale information from the registry. If all these attempts to
  discover an initial locale from the user's environment fail, msgcat defaults
  to an initial locale of “C”.

When a locale is specified by the user, a “best
    match” search is performed during string translation. For example, if
    a user specifies en_GB_Funky, the locales “en_GB_Funky”,
    “en_GB”, “en” and (the empty string) are
    searched in order until a matching translation string is found. If no
    translation string is available, then ::msgcat::mcunknown is
  called.








Strings stored in the message catalog are stored relative to the
    namespace 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 to be shorter and less prone to typographical
    error.


For example, executing the code




::msgcat::mcset en hello "hello from ::"
namespace eval foo {
   ::msgcat::mcset en hello "hello from ::foo"
}
puts [::msgcat::mc hello]
namespace eval foo {puts [::msgcat::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
    namespace.


For example, executing (in the “en” locale) the
  code




::msgcat::mcset en m1 ":: message1"
::msgcat::mcset en m2 ":: message2"
::msgcat::mcset en m3 ":: message3"
namespace eval ::foo {
   ::msgcat::mcset en m2 "::foo message2"
   ::msgcat::mcset en m3 "::foo message3"
}
namespace eval ::foo::bar {
   ::msgcat::mcset en m3 "::foo::bar message3"
}
namespace import ::msgcat::mc
puts "[mc m1]; [mc m2]; [mc m3]"
namespace eval ::foo {puts "[mc m1]; [mc m2]; [mc m3]"}
namespace eval ::foo::bar {puts "[mc m1]; [mc m2]; [mc m3]"}



will print



:: message1; :: message2; :: message3
:: message1; ::foo message2; ::foo message3
:: message1; ::foo message2; ::foo::bar message3










Message files can be located in any directory, subject to the
    following conditions:



  
[1]

  
All message files for a package are in the same directory.

  
[2]

  
The message file name is a msgcat locale specifier (all lowercase)
      followed by “.msg”. For example:






es.msg    — spanish
en_gb.msg — United Kingdom English



Exception: The message file for the root locale is called
  “ROOT.msg”. This exception is made so as not to cause
  peculiar behavior, such as marking the message file as “hidden”
  on Unix file systems.


  
[3]

  
The file contains a series of calls to mcset and mcmset,
      setting the necessary translation strings for the language, likely
      enclosed in 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!"
}










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 language files, stored in msgs subdirectory
::msgcat::mcload [file join [file dirname [info script]] msgs]










It is possible that a message string 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 produced %d units in location %s" $num $city
format "In location %s we produced %d units" $city $num




This can be handled by using the positional parameters:




format "We produced %1\$d units in location %2\$s" $num $city
format "In location %2\$s we produced %1\$d units" $num $city




Similarly, positional parameters can be used with scan to
    extract values from internationalized strings.








The message catalog code was developed by Mark Harrison.








format(n), scan(n), namespace(n), package(n)








internationalization, i18n, localization, l10n, message, text,
    translation







  

    1.4
    msgcat