Purpose: information relating to the message catalog interface.
Documentation can be found at http://www.purl.org/tcl/home/man/tcl8.5/TclCmd/msgcat.htm
The msgcat package (standard with Tcl since 8.1) addresses the problem of hard coded application text.
Instead of
label .x -text Files
if you write
label .x -text [mc Files]
then you can create catalog entries for various languages for the term "Files". Also, mc will apply formatting to the string, so
puts [mc "Directory contains %d files" $nfiles]
will allow a translator to work with the string "Directory contains %d files".
The above example assumes you have once invoked
package require msgcat ;# and done namespace import msgcat::* ;# (or msgcat::mc).
Provided you have .msg files containing
::msgcat::mcset de Files Dateien ::msgcat::mcset fr Files Fichiers
(notice that the rootname part has the naming convention that it shall be the contained language - for e.g. locale "en_us_funky", msgcat searches the contents of first en_us_funky.msg, then en_us.msg, then en.msg) then either automagically (when env(LANG) is accordingly set) or by
::msgcat::mclocale fr
.x will have the text "Fichiers".
If you want to package your messages into the application file, you can as well do this with mcset. See Multilingual menu and A little stopwatch for examples.
Note that msgcat 1.3 (comes with Tcl 8.4) also initializes the locale from ::env(LC_ALL) or ::env(LC_MESSAGES).
LES: I don't have ::env(LC_ALL) and ::env(LC_MESSAGES) on Slackware 11.
Arjen Markus This came up in the newsgroup:
The utility frink is able to adjust the source code so that the new code uses the msgcat package.
The 8.3.4 release of the PPC binary is broken in that it lacks msgcat and bgerror implementations. Melissa Schrumpf explains the situation with her customary clarity
... bgerror and msgcat are contained in tcl/library/msgcat/msgcat.tcl.
Do this:
Copy "Simply Tk (PPC)" to "Simply Tk (PPC).edit"
Run ResEdit (or Resourcer, or whathaveyou). Open a "Simply Tk
(PPC).edit" in ResEdit. Open the "TEXT" resources. Open resource ID
"package require msgcat"
This will be right at the top.
Next, open tcl/library/msgcat/msgcat.tcl in a text editor. Copy from
the beginning of the line:
package provide msgcat 1.1.1
through to the end of the file.
Return to ResEdit. Delete the line "package require msgcat" and,
in its place, paste the code you copied from msgcat.tcl.
Close all resources and save.
You now have a fixed stand-alone Tk shell.
Anton Kovalenko has written, "Also, there is a small but useful script, which converts non-ascii characters from current system encoding to \uXXXX sequences. I think it would be useful to anyone who works often with tcl message catalogs. http://kovalenko.webzone.ru/unicodize.tcl (A/AK: chat.ru is down, so my page migrated) "
LES: "Forbidden. You don't have permission to access /unicodize.tcl on this server."
A/AK: there are some things about msgcat and shortcut keys, that are important for GUI application writers. EKB And this seems to have been continued into ampersand magic.
KHM Any Idea where to download this tool?
LV KHM - msgcat is a part of Tcl itself. Or are you talking about some other tool?
GNU gettext has support (since V 0.13 [L1 ]) for Tcl msgcat and conversion tools from and to PO format. http://ftp.gnu.org/gnu/gettext/
Simple Tk example of switching languages, complements of dgp:
package require Tk bgerror 123 msgcat::mclocale "fr" msgcat::mcload [file join $::tk_library msgs] bgerror 123 msgcat::mclocale "en_gb" msgcat::mcload [file join $::tk_library msgs] bgerror 123
Now, how can I determine what languages are available for mclocale?
escargo 8 Dec 2003 - What if you want to do some form of parameter substitution in the strings that you might use with msgcat? In some systems I have developed, messages were somewhat macro-like; you might pass a number or a name (of a file, for example) that should be part of the message. Is there anything in the msgcat that does the substitution internally, or do I have to add my own layer on top of it?
RS: Easy, for instance with format:
msgcat::mcset fr "Directory contains %d files" "Il y a %d fichiers" ... puts [format [mc "Directory contains %d files"] $nfiles]
DGP Even easier. There's a format already built-in to mc:
puts [mc "Directory contains %d files" $nfiles]
EKB I moved this example up to the top of the page and combined it with the intro text so it's easier to find.
AM Also very useful: the %1$s type format codes - with this you can interchange variables if needed.
% mc "this is a %s test for %s" first anything
this is a first test for anything
% mc {this is a %2$s test for %1$s} first anything
this is a anything test for firstNote the {} around the text to prevent the $ to be interpreted and looking for the variable $s.
RS 2007-01-08: Here's a simple self-contained example for testing:
#!/usr/bin/env tclsh
package require msgcat
msgcat::mcset de yes Ja
msgcat::mcset de no Nein
msgcat::mcset fr yes Oui
msgcat::mcset fr no Non
proc localbool value {
if {$value} {msgcat::mc yes} else {msgcat::mc no}
}
puts [localbool 0]/[localbool 1]
That's all. Save that to a file, and run it with different LANG settings:
$ /Tcl/msgcat.tcl
Nein/Ja
$ LANG=fr /Tcl/msgcat.tcl
Non/Oui
$ LANG=en /Tcl/msgcat.tcl
no/yesHaO 2012-07-17: TIP 399 contains a patch to use msgcat in an environment which dynamically changes languages.
A file msgcat-1.5.0.tm is available in the linked feature request #3511941 . This file may be put to the tcl lib to be tested. In my experience, it is not sufficient, to have the file within the own project. It must be copied to the tcl installation beside the present file msgcat-1.4.4.tm.
HaO 2012-08-27: Two things happened:
What I would prefer is to vote YES for the "turn the whole
package over to Harald Oehlmann to do as he pleases".
The proposal seems fine, to address the problem posed.
What gives me pause is that the TIP seems to demonstrate that
the original design of msgcat just isn't any good. At some
point we'd be better off not slapping in more bells and whistles
and alternatives and just creating a new (version of a?) package
that learns the lessons and gets it right this time.
I came to the conclusion, that dynamic local change is wanted but the proposed solution only solves parts of the issue. Here is an extract of my message on the core-list:
Unfortunately, the solution within the tip is half-baken and I ask for some time to design a better solution and rewrite a tip.
I am sorry for that but I am convinced, this is the best way to go. I might be wrong, but at least I will try.
A good solution for TIP 399 must automatically reload locale files on a locale change.
There is a new command to set per caller namespace config data (namespace equal package, as each package should have one namespace and one set of locale files):
msgcat::mcpackageconfig ?-namespace namespace? setting ?value?
Settings per caller namespace/package:
All of them are get and setable. The function returns with an error, if the namespace does not exist.
The advantages of this:
There are the following additional configuration settings:
HaO 2012-08-22: AK asked by private mail:
Do we have a <<LocaleChanged>> virtual event like we have <<ThemeChanged>>, which is used to inform all widgets when 'mclocale' was switched at runtime ?
HaO answered:
No, we dont have this currently.
As it is a tcl-only package, we do not have the bind command.
Thus we could register a command which is called when the locale changes:
msgcat::mcconfig -command ?lcmd?
When the command fails, bgerror is called. An eventual locale change command (ex: msgcat::mclocale en_us), which executes the commands does not return with an error if a locale change callback fails.
Example:
package provide mymodule 1.0
namespace eval mymodule {
# Register a locale change callback
msgcat::mcconfig -command [list myLocaleChanged]
...
# Unregister the locale change callback
msgcat::mcconfig -command ""
}AK 2012-08-22 by E-Mail:
> As it is a tcl-only package, we do not have the bind command.
True. Nor the 'event generate'.
I had thought about auto-detecting a Tk environment to restrict when it broadcasts a change, however your idea with a configurable callback is better, from an architectural point of view.
Hm. ... Hadn't thought about multiple callbacks. Guess because I was thinking in terms of events, where I can bind multiple things as I see fit.
This restriction to one-per-namespace, and providing it through a list ... I do not like that too much. It is workable, true. Still don't like it. This shoehorning multiple callbacks through a single config option feels wrong.
For multiple callbacks I would use dedicated (un)register commands, and tokens. I.e.
msgcat::register <cmdprefix>
returns a token, which is then the argument to
msgcat::unregister <token>
to identify the callbacks and remove them individually.
See http://docs.activestate.com/activetcl/8.5/tcllib/uev/uevent.html for an example of how I did that for a tcl event package.
WHD 2012-08-22 by E-Mail:
See also the hook module in Tcllib.
HaO 2012-08-27: Discussion continues in the upper point Dynamic mode - change locale on run-time. There I write, why I prefer namespace instead of tolkens.
MG 2012-08-22: I use something similar to this in his app:
proc setLocale {new_locale} {
variable locales;
variable current_locale;
set split [split $new_locale "_"]
set preflist [list]
for {set i 0} {$i < [llength $split]} {incr i} {
lappend preflist [join [lrange $split 0 end-$i] "_"]
}
set current_locale ""
foreach x $preflist {
if { [info exists locales($x)] } {
set current_locale $x
break;
}
}
if { ![info exists current_locale] || $current_locale eq "" } {
set current_locale "en_gb"
}
# Set our best available
::msgcat::mclocale $current_locale
# Update display to make sure we're using it
if { $skin ne "" } {
::skin::${skin}::locale
}
setUpMenu
setAppTitle
return;
};# setLocaleThe $locales array records exactly which locales I've loaded some form of translation for, since msgcat doesn't seem to expose that information. The code makes sure that there actually is a translation for the requested locale, and picks a less specific one if necessary in much the same way msgcat does. It falls back on en_gb as a default. Like msgcat, all the locale names are stored entirely in lowercase (en_gb not en_GB). The code after the last comment calls various procs which alter existing GUI elements to use the new locale, but could easily be replaced with something like
proc rchildren {widget} {
event generate $widget <<LocaleChanged>>
foreach x [winfo children $widget] {
rchildren $x
}
}
rchildren .so you could bind to <<LocaleChanged>> for the assorted widgets instead.
HaO 2012-08-27: Thank you, Mike, for the contribution. The language change is user level and should still work as you do it, but this is slightly off-topic. Andreas is asking, how non-user packages which store translated messages somehow (like the tcllib tooltip package) may by their action be informed about a locale change.
HaO 2012-09-06: As the solution of TIP399 was half baken, here is a new proposal. See feature request [L2 ] containing msgcat 1.6 and a prepared TIP for review.
% msgcat::mclocale en
en
% namespace eval p1 { msgcat::mcload msgs }
... will load message files en.msg and ROOT.msg from folder msgs
...
% msgcat::mclocale fr
...will load fr.msg from folder msgs and locale will be availableA package may inform itself about locale change:
% namespace eval p1 {msgcat::mcpackageconfig changecmd updateGUI}
% msgcat::mclocale de
...will load de.msg from folder msgs and locale will be available
...will invoke "::pi::updateGUI de {}"Using a load callback, catalog data may be fetched from other sources like a data base instead/in addition to message files:
namespace eval db {
msgcat::mcpackageconfig loadcmd loadMessages
msgcat::mcconfig loadedpackages\
[concat [msgcat::mcconfig loadedpackages] [namespace current]]
proc loadMessages args {
foreach locale $args {
if {[LocaleInDB $locale]} {
msgcat::mcmset $locale [GetLocaleList $locale]
}
}
}
}Refer to the tip below for details.
TIP: 399BIS Title: Dynamic Locale Changing for msgcat with on-demand File Load Version: $Revision: 1.0 $ Author: Harald Oehlmann <[email protected]> State: Draft Type: Project Vote: Done Created: 06-Sep-2012 Post-History: Keywords: Tcl,localization,msgcat Tcl-Version: 8.6
This TIP adds dynamic locale switching capabilities to the msgcat package.
Within a multi-language application like a web-server, one may change the locale quite frequently, for example if users with different locales are requesting pages. Unfortunately, this does not fit well with the model adopted by the msgcat package, which assumes that all code follows this sequence:
1. Set locale list: '''mclocale''' ''locale'' 2. Load language files with other package load: '''mcload''' ''msg-folder'' 3. Translate strings: '''mc''' ''key args...''
Note that if the locale should be changed after other packages are loaded, one must restart at step 2. This requires reloading all packages which is mostly not practical.
The aim of this tip is to extend the package by dynamic locale change capabilities.
msgcat will reload any missing message catalog files of all currently loaded packages on a locale change.
This tip compares to tip399 that the package is able to load message catalog files on demand, e.g. specially on a locale change.
A client package is a package which uses msgcat. A unique namespace is required for each client package. Within msgcat, namespace and package is always connected.
Up to now, the msgcat package used this namespace as an identifier to store the catalog data of a certain package.
This is now extended to additional properties which are stored for a package.
msgcat stores message catalog data in dependency of the locale, the package and the key (see mcset command).
The msgcat package maintains two new state lists:
The message catalog data always corresponds to these lists. The listed locals and packages are currently present.
Those lists may be get or set by the new command mcconfig. They may also be changed my mcload or mclocale.
A new option removeobsoletelocale controls, if any currently unneded locale data is discarded.
Those options are exposed by the following new command:
> '''msgcat::mcconfig option''' ?''value''?
where option is one of the above options loadedlocales, loadedpackages or removeobsoletelocale.
The initial default values are emty lists and false.
An option may be read by not specifying a value. If a value is given, the option is set. Setting those options may lead to deletion or loading of message catalog data as described in the two chapers below loadedlocales change action and loadedpackages change action.
msgcat maintains 3 options per client package.
Those options may be get or set using:
> '''msgcat::mcpackageconfig ?-package namespace? option ?value?
The optional argument -package specifies the client package namespace of the option. If it is not given, the caller namespace is used. This package must not be included in the list loadedpackages. The namespace must not exist.
Available options are:
The options are cleared if set to the empty string.
This is the message folder of the package.
On locale change, message files may be reloaded on the following conditions:
Setting this value is identical to an mcload in the given namespace and performs the following actions:
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.
See chapter callback invokation below. The paramer list appended to this callback is the list of locales to load.
This callback is invoked when a local change was performed. Its purpose is to allow a package to update a gui.
Tk may be extended to register to this callback and to invoke a virtual event.
See chapter callback invokation below. The paramer list appended to this callback is mcpreferences. All registered packages are invoked in no particular order.
There are two callbacks as described above, packages may register to.
Callbacks are invoked under the following conditions:
The callback is invoked in the registered namespace with a set of locales as parameters as follows:
> namespace inscope $ns $callback {*}$loclistAny error within the callback stops the operation which invoked the callback. This might be surprising, as the error might be in another package.
~~ loadedpackages change action
The list of loaded packages may change in the following circumstances:
The following action is done on a list change:
The list of loaded locales may change in the following circumstances:
The following action is done on a list change:
The following steps are performed when message catalog files should be loaded:
Imagine an application which supports the current user language and French, German and English. An external package tp is used. The package uses msgcat and performes within the package require tp call:
package require msgcat msgcat::mcload [file join [file dirname [info script]] msgs]
An implementation of the application with the current msgcat 1.4.4 would require the following initialisation sequence:
package require msgcat package require np
and the following code to change the locale to French:
package forget np msgcat::mclocale fr package require np
Using the extension of this tip, one may load as usual:
package require msgcat package require np
and to change to french locale:
msgcat::mclocale fr
The first time, a locale is required, all corresponding message files of all packages which use msgcat get loaded. This might be a heavy operation.
If a locale is reactivated (and the message catalog data was not cleared), it is a quick operation.
Without this tip, it is computational expensive (if possible, as many packages are not reloadable or a reload may disturb current processing, e.g., by forcing the closing of sockets, etc.).
If it is shure, that a locale is changed and the then obsolete data is of no use, one may activate its removal:
msgcat::mclocale fr msgcat::mcconfig removeobsoletelocale 1
or
msgcat::mcconfig removeobsoletelocale 1 msgcat::mclocale fr
Packages which display a gui may update their widgets when the 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
msgcat::mcconfig loadedpackages\
[concat [msgcat::mcconfig loadedpackages] [namespace current]]
proc loadMessages args {
foreach locale $args {
if {[LocaleInDB $locale]} {
msgcat::mcmset $locale [GetLocaleList $locale]
}
}
}
}See Tcl Feature Request 360894 ,
Imagined incompatibilities:
Imagined issues:
The alternative is the former TIP399. This will IMHO not work, as the list of locales must be known before any package load. If the easy of this patch is once experienced, nobody would accept the burden.
This document has been placed in the public domain.
HaO 2012-07-17: I find it anoying and error-prone to repeate the locale for each mcset-command, even if it could already be known by the file name of the message catalog file.
As a consequence, one may try the extension of msgcat in the feature request #3544988 (patch, package and tclapp tap-file available in the download section) (updated 2012-07-25, namespace bug).
This extension basicly adds variants of the mcset and mcmset commands to use the locale given by the file name of the current sourced message cataloge file.
Here is an example file contents with the file name de.msg:
mcflset File Datei mcflset Exit Verlassen
The command name mcflset is an abreviation of "message catalogue with file locale set".
The mc file locale is set by the mcload command before a message file is sourced. The msgcat subcommand mcconfig is extended to get and set this locale:
% puts [mcconfig -mcfilelocale] de % mcconfig -mcfilelocale en en
The new command mcflset is identical to:
mcset [mcconfig -mcfilelocale] <src> <translation>
Old and new syntax may be mixed, for example to set local variations (this is IMHO not recommended at all, better use two message files, but I didn't find a better example):
mcflset Hello "Hallo" mcset de_CH Hello "Salü"
The set-ability of the mc file locale is not important. It might be used, to set the default value for a bunch of values within program code (and not in an msg file).
mcconfig -mcfilelocale de mcflset File Datei mcflset Exit Verlassen
One must take care, that any mcload command may set it to another value. Specially package require commands may invoke mcload commands.
HaO 2012-07-17: Given the code with a localised error message:
if {[catch {open $File r} Err]} {
puts stderr [mc "File error accessing '%s': %s" $File $Err]
}and the German translation:
--de.msg-- msgcat::mcset de "File error accessing '%s': %s" "Zugriffsfehler Datei '%s': %s" --eof--
I use tags instead of a default translation. The default (english) text is contained in the root translation:
--de.msg--
msgcat::mcset de errFile "Zugriffsfehler Datei '%s': %s"
--eof--
--ROOT.msg--
msgcat::mcset {} errFile "File error accessing '%s': %s"
--eof--
if {[catch {open $File r} Err]} {
puts stderr [mc errFile $File $Err]
}Why that ?
HaO 2012-07-24: The clock command explicitly requires msgcat 1.4. An alternate msgcat version must also be in the default path, as the clock package is loaded before any script may extend the auto_path.
Thus the new msgcat.tcl is renamed to msgcat-1.x.x.tm (1.x.x: version greater 1.4.5 which is the version in tcl 8.5.12) and saved to:
If the program is wrapped to an executable starkit (not .kit), one may save it to:
If an application is wrapped using ActiveState TclApp, I did not found any way to wrap anything to the upper path. But I made a custom tap file containing a pckIndex.tcl and a msgcat.tcl and this worked (at least for a console application). The tap-file for msgcat-1.5.1 is here: msgcat-1.5.1.zip