|Subject:||Re: doc gettext|
|Date:||Mon, 10 Jan 2005 22:11:05 +0100|
Kevin Ryde wrote: > I'm looking at the text below to expand what's in the guile reference > manual for gettext. You can also use text from my original proposal (attached). It has the merit of explaining the terms (domain, category, ...) that are used in the refman. Also it contains complete workable examples. (You need to change the set! notation to the optional-argument notation that is used in guile, though.) > I'm a bit unsure about bind-textdomain-codeset. Thinking about it, if > Guile gets its own notion of coding systems or whatever in the future > then I'm wondering if that function might become obsolete, or even > actively harmful. When that happens, the bind-textdomain-codeset function should become a nop. > It does some good now, but maybe some strong > warning against possible future change is needed. But since in the present this function is _necessary_, I don't think it's useful to make people doubt whether they should use it or not. When bind-textdomain-codeset is no longer needed, you can easily make the compiler emit a warning when it's used. Bruno
"Internationalization" means to prepare a program so that it can use multiple national languages and national cultural conventions without requiring further source code changes. Localization means providing the data - mostly textual translations - necessary for an internationalized program to work in a particular language and with particular cultural conventions.
GNU gettext is a set of functions, included in guile or the C library, which permit looking up translations of strings through message catalogs. It is also a set of tools which makes the translation maintenance easy for the translator and the program maintainer.
The DOMAIN is a string identifier denoting the program that is requesting the translation. The pathname of the message catalog depends on the DOMAIN: usually it is located at TEXTDOMAINDIR/l/LC_MESSAGES/domain.mo, where l is the ISO 639 code of the language. The notion of DOMAIN allows several Lisp programs running in the same image to request translations independently of each other.
Function i18n:textdomain. (i18n:textdomain) is a place that returns the default DOMAIN, used when no DOMAIN argument is passed to the i18n:gettext and i18n:ngettext functions. It is SET!able. SET! i18n:textdomain is usually used during the startup phase of a program. Note that the default DOMAIN is not saved in a memory image. The use of SET! i18n:textdomain is recommended only for programs that are so simple that they will never need more than one DOMAIN.
Function i18n:textdomaindir. (i18n:textdomaindir
is a place
that returns the base directory, called
TEXTDOMAINDIR above, where the message
catalogs for the given DOMAIN are assumed to be
It is SET!able. SET! i18n:textdomaindir
is usually used
during the startup phase of a program, and should be used because only
the program knows where its message catalogs are installed.
Note that the TEXTDOMAINDIRs
are not saved in a memory image.
Function i18n:textdomain-codeset. (i18n:textdomain-codeset
is a place that returns the specified encoding for the
strings returned by i18n:gettext
and i18n:ngettext. The
default value is #f, denoting the default locale encoding. It is SET!able. The value it is
set to must be an encoding name known to the system iconv() function. SET! i18n:textdomain-codeset
is usually used
during the startup phase of a program whose internal string
representation is not in the default locale encoding.
Note that the TEXTDOMAIN-CODESETs
are not saved in a memory image.
The CATEGORY argument of the i18n:gettext and i18n:ngettext functions denotes which locale facet the result should depend on. The default value is :LC_MESSAGES. Other possible values are :LC_CTYPE, :LC_TIME, :LC_COLLATE, :LC_MONETARY. The use of these values is useful for users who have a character/time/collation/money handling set differently from the usual message handling. Note that when a CATEGORY argument is used, the message catalog location depends on the CATEGORY: it will be expected at TEXTDOMAINDIR/ll/category/domain.mo.
A non-internationalized program simulating a restaurant dialogue might look as follows.
Example 1. prog.scm
(define n (parse-integer (first *ARGS*)))
After being internationalized, all strings are wrapped in i18n:gettext calls, and i18n:ngettext is used for plurals. Also, i18n:textdomaindir is assigned a value; in our case, for simplicity, the current directory.
Example 2. prog.scm
(set! (textdomain) "prog")
For ease of reading, it is customary to define an abbreviation for the i18n:gettext function. An underscore is customary.
Example 3. prog.scm
(set! (textdomaindir "prog") "./")
Now the program's maintainer creates a message catalog template through the command
bash$ xgettext -o prog.pot prog.scm
xgettext version 0.14.2 or higher is required here.
The message catalog template looks roughly like this.
Example 29.4. prog.pot
msgid "'Your command, please?', asked the waiter."
Then a French translator creates a French message catalog
Example 29.5. prog.fr.po
and sends it to the program's maintainer.
The program's maintainer compiles the catalog as follows:
bash$ mkdir -p ./fr/LC_MESSAGES
When a user in a french locale then runs the program
bash$ guile prog.scm 2
she will get the output
Â«Votre commande, s'il vous plaitÂ», dit le garÃ§on.
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