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msgcat(n)                    Tcl Bundled Packages                    msgcat(n)



______________________________________________________________________________


NAME

       msgcat - Tcl message catalog


SYNOPSIS

       package require Tcl 8.5

       package require msgcat 1.6

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

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

       ::msgcat::mcexists ?-exactnamespace? ?-exactlocale? src-string          |

       ::msgcat::mclocale ?newLocale?

       ::msgcat::mcpreferences

       ::msgcat::mcloadedlocales subcommand ?locale?                           |

       ::msgcat::mcload dirname

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

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

       ::msgcat::mcflset src-string ?translate-string?

       ::msgcat::mcflmset src-trans-list

       ::msgcat::mcunknown locale src-string ?arg arg ...?

       ::msgcat::mcpackagelocale subcommand ?locale?                           |

       ::msgcat::mcpackageconfig subcommand option ?value?                     |

       ::msgcat::mcforgetpackage
______________________________________________________________________________


DESCRIPTION

       The msgcat package provides a set of functions that can be used to man-
       age multi-lingual user interfaces.  Text strings are defined in a "mes-
       sage  catalog" which is independent from the application, and which can
       be edited or localized without modifying the application  source  code.
       New  languages  or  locales may be provided by adding a new file to the
       message catalog.

       msgcat distinguises packages by its namespace.  Each  package  has  its
       own message catalog and configuration settings in msgcat.

       A  locale  is  a  specification  string describing a user language like
       de_ch for Swiss German.  In msgcat, there is a global  locale  initial-
       ized  by  the  system  locale  of the current system.  Each package may
       decide to use the global locale or to use a package specific locale.

       The global locale may be changed on demand, for example by a user  ini-
       tiated  language  change  or within a multi user application like a web
       server.


COMMANDS

       ::msgcat::mc src-string ?arg arg ...?
              Returns a translation of src-string  according  to  the  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  applica-
              tion.   Instead of using an English string directly, an applica-
              tion 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::mcexists ?-exactnamespace? ?-exactlocale? src-string
              Return true, if there is a translation for the given src-string. |

              The  search may be limited by the option -exactnamespace to only |
              check the current namespace and not any parent namespaces.       |

              It may also be limited by the option -exactlocale to only  check |
              the first prefered locale (e.g. first element returned by ::msg- |
              cat::mcpreferences if global locale is used).                    |

       ::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 low-
              ercase.  The initial locale is determined by the  locale  speci-
              fied  in the user's environment.  See LOCALE SPECIFICATION below
              for a description of the locale string format.

              If the locale is set, the preference list of locales  is  evalu- |
              ated.  Locales in this list are loaded now, if not jet loaded.

       ::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:mcloadedlocales subcommand ?locale?
              This  group  of  commands  manage the list of loaded locales for
              packages not setting a package locale.

              The subcommand get returns the list of currently loaded locales.

              The  subcommand present requires the argument locale and returns
              true, if this locale is loaded.

              The subcommand clear removes all locales and their  data,  which
              are not in the current preference list.

       ::msgcat::mcload dirname
              Searches  the  specified directory for files that match the lan- |
              guage specifications returned by  ::msgcat::mcloadedlocales  get |
              (or  msgcat::mcpackagelocale  preferences if a package locale is |
              set) (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.                                         |

              In  addition,  the  given folder is stored in the msgcat package |
              configuration option mcfolder to eventually load message catalog |
              files required by a locale change.

       ::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::mcflset src-string ?translate-string?
              Sets the translation for src-string to translate-string  in  the
              current namespace for the locale implied by the name of the mes-
              sage catalog being loaded via ::msgcat::mcload.   If  translate-
              string is not specified, src-string is used for both.  The func-
              tion returns translate-string.

       ::msgcat::mcflmset src-trans-list
              Sets the translation for multiple source strings  in  src-trans-
              list in the current namespace for the locale implied by the name
              of the message catalog being loaded via  ::msgcat::mcload.  src-
              trans-list  must  have  an even number of elements and is in the
              form {src-string translate-string  ?src-string  translate-string
              ...?} ::msgcat::mcflmset can be significantly faster than multi-
              ple invocations of ::msgcat::mcflset. The function  returns  the
              number of translations set.

       ::msgcat::mcunknown locale src-string ?arg arg ...?
              This routine is called by ::msgcat::mc in the case when a trans-
              lation for src-string is not defined in the current locale.  The
              default action is to return src-string passed by format if there
              are any arguments.  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.                                            |

              Note  that  this routine is only called if the concerned package |
              did not set a package locale unknown command name.               |

       ::msgcat::mcforgetpack-                                                 |
       age                                               |                     |
              The calling package clears all its state within the msgcat pack- |
              age including all settings and translations.



LOCALE SPECIFICATION

       The locale is specified to msgcat by a locale string passed  to  ::msg-
       cat::mclocale.   The  locale  string  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 stan-
       dards 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 ::msg-
       cat::mclocale with the argument

              language[_country][_modifier]

       On Windows and Cygwin, if none of those environment variables  is  set,
       msgcat  will  attempt  to extract locale information from the registry.
       From Windows Vista on, the RFC4747  locale  name  "lang-script-country-
       options"  is  transformed to the locale as "lang_country_script" (Exam-
       ple: sr-Latn-CS -> sr_cs_latin). For Windows XP,  the  language  id  is
       transformed  analoguously  (Example:  0c1a  -> sr_yu_cyrillic).  If all
       these attempts to discover an initial locale from the  user's  environ-
       ment fail, msgcat defaults to an initial locale of "C".

       When  a  locale is specified by the user, a "best match" search is per-
       formed 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 the unknown handler
       is called.


NAMESPACES AND MESSAGE CATALOGS

       Strings stored in 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 to be shorter and less prone to typo-
       graphical 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 names-
       pace.

       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


LOCATION AND FORMAT OF MESSAGE FILES

       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 lower-
              case) 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 behav-
       ior, such as marking the message file as "hidden" on Unix file systems.

       [3]    The  file  contains  a  series of calls to mcflset and mcflmset,
              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::mcflset "Free Beer" "Cerveza Gratis"
              }


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


POSITIONAL CODES FOR FORMAT AND SCAN COMMANDS

       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 val-
       ues from internationalized strings. Note that it is  not  necessary  to
       pass the output of ::msgcat::mc to format directly; by passing the val-
       ues to substitute in as arguments, the formatting substitution is  done
       directly.

              msgcat::mc {Produced %1$d at %2$s} $num $city
              # ... where that key is mapped to one of the
              # human-oriented versions by msgcat::mcset


Package private locale |

       A package using msgcat may choose to use its own package private locale |
       and its own set of loaded locales, independent to the global locale set |
       by ::msgcat::mclocale.                                                  |

       This  allows a package to change its locale without causing any locales |
       load or removal in other packages and not to invoke the  global  locale |
       change callback (see below).                                            |

       This action is controled by the following ensemble:                     |

       ::msgcat::mcpackagelocale set                                           |
       ?locale?                                  |                             |
              Set or change a package private  locale.   The  package  private |
              locale  is  set  to the given locale if the locale is given.  If |
              the option locale is not given, the package is  set  to  package |
              private  locale  mode,  but  no  locale  is changed (e.g. if the |
              global locale was valid for the package before, it is copied  to |
              the package private locale).                                     |

              This command may cause the load of locales.                      |

       ::msgcat::mcpackagelocale                                               |
       get                                           |                         |
              Return the package private locale or the global  locale,  if  no |
              package private locale is set.                                   |

       ::msgcat::mcpackagelocale prefer-                                       |
       ences                                   |                               |
              Return the package private preferences  or  the  global  prefer- |
              ences, if no package private locale is set.                      |

       ::msgcat::mcpackagelocale                                               |
       loaded                                        |                         |
              Return the list of locales loaded for this package.              |

       ::msgcat::mcpackagelocale                                               |
       isset                                         |                         |
              Returns true, if a package private locale is set.                |

       ::msgcat::mcpackagelocale                                               |
       unset                                         |                         |
              Unset the package private locale and  use  the  globale  locale. |
              Load and remove locales to adjust the list of loaded locales for |
              the package to the global loaded locales list.                   |

       ::msgcat::mcpackagelocale present                                       |
       locale                                |                                 |
              Returns true, if the given locale is loaded for the package.     |

       ::msgcat::mcpackagelocale                                               |
       clear                                         |                         |
              Clear any loaded locales of the package not present in the pack- |
              age preferences.                                                 |



Changing package options |

       Each  package  using  msgcat  has  a set of options within msgcat.  The |
       package options are described in the next sectionPackage options.  Each |
       package  option  may  be  set or unset individually using the following |
       ensemble:                                                               |

       ::msgcat::mcpackageconfig get                                           |
       option                                    |                             |
              Return the current value of the given option.  This call returns |
              an error if the option is not set for the package.               |

       ::msgcat::mcpackageconfig isset                                         |
       option                                  |                               |
              Returns  1, if the given option is set for the package, 0 other- |
              wise.                                                            |

       ::msgcat::mcpackageconfig set option                                    |
       value                              |                                    |
              Set  the given option to the given value.  This may invoke addi- |
              tional actions in dependency of the option.  The return value is |
              0 or the number of loaded packages for the option mcfolder.      |

       ::msgcat::mcpackageconfig unset                                         |
       option                                  |                               |
              Unsets the given option for the package.  No action is taken  if |
              the  option  is  not  set  for the package.  The empty string is |
              returned.                                                        |

   Package options                                                             |
       The following package options are available for each package:           |

       mcfolder                                                                ||
              This is the message folder of the package. This option is set by |
              mcload and by the subcommand set. Both are  identical  and  both |
              return the number of loaded message catalog files.               |

              Setting  or  changing this value will load all locales contained |
              in the preferences valid for the package. This implies  also  to |
              invoke any set loadcmd (see below).                              |

              Unsetting  this  value  will  disable  message file load for the |
              package.                                                         |

       load-                                                                   |
       cmd                                                                 |   |
              This  callback  is invoked before a set of message catalog files |
              are loaded for the package which has this property set.          |

              This callback may be used to do any preparation work for message |
              file  load or to get the message data from another source like a |
              data base. In this case, no message files are used (mcfolder  is |
              unset).                                                          |

              See  section  callback  invocation  below.   The  parameter list |
              appended to this callback is the list of locales to load.        |

              If this callback is changed, it is called with  the  preferences |
              valid for the package.                                           |

       changecmd                                                               ||
              This callback is invoked when a default local  change  was  per- |
              formed.  Its  purpose is to allow a package to update any depen- |
              dency on the default locale like showing the GUI in another lan- |
              guage.                                                           |

              See  the  callback invocation section below.  The parameter list |
              appended to this  callback  is  mcpreferences.   The  registered |
              callbacks are invoked in no particular order.                    |

       unknowncmd                                                              ||
              Use a package locale mcunknown procedure instead of the standard |
              version supplied by the msgcat package (msgcat::mcunknown).      |

              The  called  procedure  must  return the formatted message which |
              will finally be returned by msgcat::mc.                          |

              A generic unknown handler is used if set to  the  empty  string. |
              This  consists  in  returning the key if no arguments are given. |
              With given arguments, format is used to process the arguments.   |

              See section callback invocation below.  The  appended  arguments |
              are identical to ::msgcat::mcunknown.                            |

   Callback invocation                                                         |
       A  package  may  decide  to  register  one  or  multiple  callbacks, as |
       described above.                                                        |

       Callbacks are invoked, if:                                              |

       1. the callback command is set,                                         |

       2. the command is not the empty string,                                 |

       3. the registering namespace exists.                                    |

       If a called routine fails with an error, the bgerror  routine  for  the |
       interpreter is invoked after command completion.  Only exception is the |
       callback unknowncmd, where an error causes the invoking  mc-command  to |
       fail with that error.                                                   |


   Examples                                                                    |
       Packages  which  display a GUI may update their widgets when the global |
       locale changes.  To register to a callback, use:                        |
              namespace eval gui {                                             |
                  msgcat::mcpackageconfig changecmd updateGUI                  |

                  proc updateGui args {                                        |
                      puts "New locale is '[lindex $args 0]'."                 |
                  }                                                            |
              }                                                                |
              % msgcat::mclocale fr                                            |
              fr                                                               |
              % New locale is 'fr'.                                            |

       If locales (or additional locales) are contained in another source like |
       a data base, a package may use the load callback and not mcload:        |
              namespace eval db {                                              |
                  msgcat::mcpackageconfig loadcmd loadMessages                 |

                  proc loadMessages args {                                     |
                      foreach locale $args {                                   |
                          if {[LocaleInDB $locale]} {                          |
                              msgcat::mcmset $locale [GetLocaleList $locale]   |
                          }                                                    |
                      }                                                        |
                  }                                                            |
              }                                                                |

       The  clock  command implementation uses msgcat with a package locale to |
       implement the command line parameter -locale.  Here are  some  sketches |
       of the implementation:                                                  |

       First, a package locale is initialized and the generic unknown function |
       is desactivated:                                                        |
              msgcat::mcpackagelocale set                                      |
              msgcat::mcpackageconfig unknowncmd ""                            |
       As an example, the user requires the week day in a  certain  locale  as |
       follows:                                                                |
              clock format clock seconds -format %A -locale fr                 |
       clock  sets the package locale to fr and looks for the day name as fol- |
       lows:                                                                   |
              msgcat::mcpackagelocale set $locale                              |
              return [lindex [msgcat::mc DAYS_OF_WEEK_FULL] $day]              |
              ### Returns "mercredi"                                           |
       Within clock, some message-catalog items are heavy in  computation  and |
       thus are dynamically cached using:                                      |
              proc ::tcl::clock::LocalizeFormat { locale format } {            |
                  set key FORMAT_$format                                       |
                  if { [::msgcat::mcexists -exactlocale -exactnamespace $key] } {|
                      return [mc $key]                                         |
                  }                                                            |
                  #...expensive computation of format clipped...               |
                  mcset $locale $key $format                                   |
                  return $format                                               |
              }                                                                |


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                                1.5                            msgcat(n)

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