TIP #399 Version 1.1: Dynamic Locale Changing for msgcat

This is not necessarily the current version of this TIP.

Abstract

This TIP adds dynamic locale switching to the msgcat package.

Rationale

The msgcat package has a 3 stage processing model:

1. Set locale list

mclocale locale

2. Load language files with other package load

mcload catalog

3. Translate strings

mc key args...

If the locale should be changed after other packages are loaded, one must restart at step 2.

Within a multi-language application like a web-server, one may change the language quite quickly, for example if users with different locales are requesting pages.

The issue is that mcload only loads language files included in the current locale (mcpreferences) and does not load any others.

The aim of this tip is to extend mcload to load additional language files. Then mclocale may be called to change the language on runtime.

Specification

This TIP proposes to add a new command:

msgcat::mcconfig -pattern ?patternlist?

This command may get or set package options. There is currently one option "-pattern". Options may be set using

msgcat::mcconfig option value ?option? ?value?

Current option values may be read using:

msgcat::mcconfig option

The option '-pattern consists of a list of language file name patterns like fr*, *, fr_ch.

Example Usage

Initialise msgcat within an application which supports the current user language and french, german and english.

package require msgcat 1.5
msgcat::mcconfig -pattern {fr.* de.* en.*}
# require any other package
package require BWidget

# switch to french
msgcat::mclocale fr

Reference Implementation

See Tcl Feature Request 3511941. [1]

Compatibility

No incompatibilities are introduced

Alternatives

This implementation requires the setting of the pattern before any package with msgcat is loaded. To avoid this, msgcat must store all paths passed by any mcload call. In case of a locale change, any currently missing files are loaded. This requires much more housekeeping and may lead to side effects, especially if packages are not aware of the fact that their package files are loaded outside of the mcload command.

Copyright

This document has been placed in the public domain.

This is not necessarily the current version of this TIP.