- NAME
- msgcat — Tcl message catalog
- SYNOPSIS
- DESCRIPTION
- COMMANDS
- ::msgcat::mc src-string ?arg arg ...?
- ::msgcat::mcn namespace src-string ?arg arg ...?
- ::msgcat::mcmax ?src-string src-string ...?
- ::msgcat::mcexists ?-exactnamespace? ?-exactlocale? ?-namespace namespace? src-string
- ::msgcat::mcpackagenamespaceget
- ::msgcat::mclocale ?newLocale?
- ::msgcat::mcpreferences ?locale preference? ...
- ::msgcat::mcloadedlocales subcommand
- ::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::mcforgetpackage
- ::msgcat::mcutil getpreferences locale
- ::msgcat::mcutil getsystemlocale
- LOCALE SPECIFICATION
- NAMESPACES AND MESSAGE CATALOGS
- LOCATION AND FORMAT OF MESSAGE FILES
- RECOMMENDED MESSAGE SETUP FOR PACKAGES
- POSITIONAL CODES FOR FORMAT AND SCAN COMMANDS
- PACKAGE PRIVATE LOCALE
- ::msgcat::mcpackagelocale set ?locale?
- ::msgcat::mcpackagelocale get
- ::msgcat::mcpackagelocale preferences ?locale preference? ...
- ::msgcat::mcpackagelocale loaded
- ::msgcat::mcpackagelocale isset
- ::msgcat::mcpackagelocale unset
- ::msgcat::mcpackagelocale present locale
- ::msgcat::mcpackagelocale clear
- CHANGING PACKAGE OPTIONS
- ::msgcat::mcpackageconfig get option
- ::msgcat::mcpackageconfig isset option
- ::msgcat::mcpackageconfig set option value
- ::msgcat::mcpackageconfig unset option
- Package options
- mcfolder
- loadcmd
- changecmd
- unknowncmd
- Callback invocation
- OBJECT ORIENTED PROGRAMMING
- 1) In class definition script
- 2) method defined in a class
- 3) method defined in a classless object
- EXAMPLES
- CREDITS
- SEE ALSO
- KEYWORDS
msgcat — Tcl message catalog
package require tcl 9.0
package require msgcat 1.7
::msgcat::mc src-string ?arg arg ...?
::msgcat::mcmax ?src-string src-string ...?
::msgcat::mcexists ?-exactnamespace? ?-exactlocale? src-string
::msgcat::mcpackagenamespaceget
::msgcat::mclocale ?newLocale?
::msgcat::mcpreferences ?locale preference? ...
::msgcat::mcloadedlocales subcommand
::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
::msgcat::mcutil subcommand ?locale?
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 may be provided by adding a new file to
the message catalog.
msgcat distinguishes 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
initialized 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 initiated
language change or within a multi user application like a web server.
Object oriented programming is supported by the use of a package namespace.
- ::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
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::mcn namespace src-string ?arg arg ...?
-
Like ::msgcat::mc, but with the message namespace specified as first
argument.
-
mcn may be used for cases where the package namespace is not the
namespace of the caller. An example is shown within the description of the
command ::msgcat::mcpackagenamespaceget below.
- ::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? ?-namespace namespace? 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
::msgcat::mcpreferences if global locale is used).
An explicit package namespace may be specified by the option -namespace.
The namespace of the caller is used if not explicitly specified.
- ::msgcat::mcpackagenamespaceget
-
Return the package namespace of the caller. This command handles all cases
described in section OBJECT ORIENTED PROGRAMMING.
-
Example usage is a tooltip package, which saves the caller package namespace
to update the translation each time the tooltip is shown:
proc ::tooltip::tooltip {widget message} {
...
set messagenamespace [uplevel 1 {::msgcat::mcpackagenamespaceget}]
...
bind $widget [list ::tooltip::show $widget $messagenamespace $message]
}
proc ::tooltip::show {widget messagenamespace message} {
...
set message [::msgcat::mcn $messagenamespace $message]
...
}
- ::msgcat::mclocale ?newLocale?
-
If newLocale is omitted, the current locale is returned, otherwise the
current locale is set to newLocale.
-
If the new locale is set to newLocale, the corresponding preferences
are calculated and set.
For example, if the current locale is en_US_funky, then
::msgcat::mcpreferences returns {en_us_funky en_us en {}}.
The same result may be achieved by ::msgcat::mcpreferences
{*}[::msgcat::mcutil getpreferences newLocale].
The current locale is always the first element of the list returned by
mcpreferences.
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.
If the locale is set, the preference list of locales is evaluated.
Locales in this list are loaded now, if not jet loaded.
- ::msgcat::mcpreferences ?locale preference? ...
-
Without arguments, returns an ordered list of the locales preferred by
the user.
The list is ordered from most specific to least preference.
-
A set of locale preferences may be given to set the list of locale preferences.
The current locale is also set, which is the first element of the locale
preferences list.
Locale preferences are loaded now, if not jet loaded.
As an example, the user may prefer French or English text. This may be
configured by:
::msgcat::mcpreferences fr en {}
- ::msgcat::mcloadedlocales subcommand
-
This group of commands manage the list of loaded locales for packages not
setting a package locale.
-
The subcommand loaded returns the list of currently loaded locales.
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 language specifications returned by ::msgcat::mcloadedlocales loaded
(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 message catalog
being loaded via ::msgcat::mcload. If translate-string is not
specified, src-string is used for both. The function 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 multiple 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 translation 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::mcforgetpackage
-
The calling package clears all its state within the msgcat package
including all settings and translations.
- ::msgcat::mcutil getpreferences locale
-
Return the preferences list of the given locale as described in the section
LOCALE SPECIFICATION.
An example is the composition of a preference list for the bilingual region
"Biel/Bienne" as a concatenation of swiss german and swiss french:
% concat [lrange [msgcat::mcutil getpreferences fr_CH] 0 end-1] [msgcat::mcutil getpreferences de_CH]
fr_ch fr de_ch de {}
- ::msgcat::mcutil getsystemlocale
-
The system locale is returned as described by the section
LOCALE SPECIFICATION.
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 and Cygwin, if none of those environment variables is set,
msgcat will attempt to extract locale information from the registry.
The RFC4747 locale name "lang-script-country-options"
is transformed to the locale as "lang_country_script" (Example:
sr-Latn-CS -> sr_cs_latin).
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
the unknown handler 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:
-
All message files for a package are in the same directory.
-
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.
-
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"
}
If a package is installed into a subdirectory of the
tcl_pkgPath and loaded via package require, the
following procedure is recommended.
-
During package installation, create a subdirectory
msgs under your package directory.
-
Copy your *.msg files into that directory.
-
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 $city
Similarly, positional parameters can be used with scan to
extract values from internationalized strings. Note that it is not
necessary to pass the output of ::msgcat::mc to format
directly; by passing the values to substitute in as arguments, the
formatting substitution is done directly.
msgcat::mc {Produced %1$d at %2$s} $num $city
# ... where that key is mapped to one of the
# human-oriented versions by msgcat::mcset
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 preferences ?locale preference? ...
-
With no parameters, return the package private preferences or the global
preferences, if no package private locale is set.
The package locale state (set or not) is not changed (in contrast to the
command ::msgcat::mcpackagelocale set).
-
If a set of locale preferences is given, it is set as package locale preference
list. The package locale is set to the first element of the preference list.
A package locale is activated, if it was not set so far.
Locale preferences are loaded now for the package, if not yet loaded.
- ::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 global 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 package preferences.
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 otherwise.
- ::msgcat::mcpackageconfig set option value
-
Set the given option to the given value.
This may invoke additional 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.
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.
- loadcmd
-
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 performed. Its
purpose is to allow a package to update any dependency on the default locale
like showing the GUI in another language.
-
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 of
returning the key if no arguments are given. With given arguments, the
format command is used to process the arguments.
See section callback invocation below.
The appended arguments are identical to msgcat::mcunknown.
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.
msgcat supports packages implemented by object oriented programming.
Objects and classes should be defined within a package namespace.
There are 3 supported cases where package namespace sensitive commands of msgcat
(mc, mcexists, mcpackagelocale, mcforgetpackage,
mcpackagenamespaceget, mcpackageconfig, mcset and mcmset)
may be called:
- 1) In class definition script
-
msgcat command is called within a class definition script.
namespace eval ::N2 {
mcload $dir/msgs
oo::class create C1 {puts [mc Hi!]}
}
- 2) method defined in a class
-
msgcat command is called from a method in an object and the method is
defined in a class.
namespace eval ::N3Class {
mcload $dir/msgs
oo::class create C1
oo::define C1 method m1 {
puts [mc Hi!]
}
}
- 3) method defined in a classless object
-
msgcat command is called from a method of a classless object.
namespace eval ::N4 {
mcload $dir/msgs
oo::object create O1
oo::objdefine O1 method m1 {} {
puts [mc Hi!]
}
}
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
database, 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
deactivated:
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
follows:
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
}
The message catalog code was developed by Mark Harrison.
format, scan, namespace, package, oo::class, oo::object
internationalization, i18n, localization, l10n, message, text, translation, class, object
Copyright © 1998 Mark Harrison.