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Native Language Support (NLS)

Browse Source 
Use --enable-nls to turn it on; see installation instructions for details.
See developer's guide how to make use of it in programs and how to add
translations.

psql sources have been almost fully prepared and an incomplete German
translation has been provided.  In the backend, only elog() calls are
currently translatable, and the provided German translation file is more
of a placeholder.
This commit is contained in:
Peter Eisentraut
2001-06-02 18:25:18 +00:00
parent 58193c5f37
commit e542036461
27 changed files with 13814 additions and 600 deletions
Download Patch File Download Diff File Expand all files Collapse all files

3
doc/src/sgml/developer.sgml
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<!-- $Header: /cvsroot/pgsql/doc/src/sgml/Attic/developer.sgml,v 1.4 2001/02/03 19:03:26 petere Exp $ -->
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/Attic/developer.sgml,v 1.5 2001/06/02 18:25:16 petere Exp $ -->
<!-- PostgreSQL Developer's Guide -->
<book id="developer">
@ -24,6 +24,7 @@
&bki;
&page;
&geqo;
&nls;
<![%single-book;[
&biblio;
]]>

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doc/src/sgml/filelist.sgml
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<!-- $Header: /cvsroot/pgsql/doc/src/sgml/filelist.sgml,v 1.12 2001/05/12 22:51:34 petere Exp $ -->
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/filelist.sgml,v 1.13 2001/06/02 18:25:16 petere Exp $ -->
<!entity history SYSTEM "history.sgml">
<!entity info SYSTEM "info.sgml">
@ -96,6 +96,7 @@
<!entity page SYSTEM "page.sgml">
<!entity protocol SYSTEM "protocol.sgml">
<!entity sources SYSTEM "sources.sgml">
<!entity nls SYSTEM "nls.sgml">
<!-- see standalone-install.sgml about these -->
<!entity % flattext-install-ignore "INCLUDE">

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doc/src/sgml/installation.sgml
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<!-- $Header: /cvsroot/pgsql/doc/src/sgml/installation.sgml,v 1.49 2001/05/14 16:16:52 momjian Exp $ -->
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/installation.sgml,v 1.50 2001/06/02 18:25:16 petere Exp $ -->
<chapter id="installation">
<title><![%flattext-install-include[<productname>PostgreSQL</>]]>
@ -536,6 +536,44 @@ su - postgres
</listitem>
</varlistentry>
<varlistentry>
<term>--enable-nls<optional>=<replaceable>LANGUAGES</replaceable></optional></term>
<listitem>
<para>
Enables Native Language Support (NLS), that is, the ability
to display a program's message in a language other than
English. <replaceable>LANGUAGES</replaceable> is a space
separated list of codes of the languages that you want
supported. (The intersection between your list and the set
of actually provided translations will be computed
automatically.) If you do not specify it, then all available
translations are installed.
</para>
<comment>
The list of provided translations should be shown somewhere.
</comment>
<para>
To use this option, you will need an implementation of the
gettext API. Some operating systems have this built-in
(e.g., Linux, NetBSD, Solaris), for other systems you can download
an add-on package from here: <ulink
url="http://www.postgresql.org/~petere/gettext.html"
>http://www.postgresql.org/~petere/gettext.html</ulink>. If
you are using the gettext implementation in the GNU C library
then you will additionally need the GNU gettext package for
some utility programs. For any of the other implementations
you will not need it.
</para>
<comment>
The download location should be moved.
</comment>
</listitem>
</varlistentry>
<varlistentry>
<term>--with-pgport=<replaceable>NUMBER</></term>
<listitem>

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doc/src/sgml/nls.sgml Normal file
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<!-- $Header: /cvsroot/pgsql/doc/src/sgml/nls.sgml,v 1.1 2001/06/02 18:25:16 petere Exp $ -->
<chapter id="nls">
<docinfo>
<author>
<firstname>Peter</firstname>
<surname>Eisentraut</surname>
</author>
</docinfo>
<title>Native Language Support</title>
<sect1 id="nls-translator">
<title>For the Translator</title>
<para>
PostgreSQL programs (server and client) can issue their messages in
your favorite language -- if the messages have been translated.
Creating and maintaining translated message sets needs the help of
people who speak their own language well and want to contribute to
the PostgreSQL effort. You do not have to be a programmer at all
to do this. This section explains how to help.
</para>
<sect2>
<title>Requirements</title>
<para>
We won't judge your language skills -- this section is about
software tools. Theoretically, you only need a text editor. But
this is only in the unlikely event that you do not want to try out
your translated messages. When you configure your source tree, be
sure to use the <option>--enable-nls</option> option. This will
also check for the libintl library and the
<filename>msgfmt</filename> program, which all end users will need
anyway. To try out your work, follow the applicable portions of
the installation instructions.
</para>
<para>
If you want to start a new translation effort or want to do a
message catalog merge (described later), you will need the
programs <filename>xgettext</filename> and
<filename>msgmerge</filename>, respectively, in a GNU-compatible
implementation. Later, we will try to arrange it so that if you
use a packaged source distribution, you won't need
<filename>xgettext</filename>. (From CVS, you will still need
it.) GNU gettext 0.10.36 or later is currently recommended.
</para>
<para>
Your local gettext implementation should come with its own
documentation. Some of that is probably duplicated in what
follows, but for additional details you should look there.
</para>
</sect2>
<sect2>
<title>Concepts</title>
<para>
The pairs of original (English) messages and their (possibly)
translated equivalents are kept in <firstterm>message
catalogs</firstterm>, one for each program (although related
programs can share a message catalog) and for each target
language. There are two file formats for message catalogs: The
first is the <quote>PO</quote> file (for Portable Object), which
is a plain text file with special syntax that translators edit.
The second is the <quote>MO</quote> file (for Machine Object),
which is a binary file generated from the respective PO file and
is used while the internationalized program is run. Translators
do not deal with MO files; in fact hardly anyone does.
</para>
<para>
The extension of the message catalog file is to no surprise either
<filename>.po</filename> or <filename>.mo</filename>. The base
name is either the name of the program it accompanies, or the
language the file is for, depending on the situation. This is a
bit confusing. Examples are <filename>psql.po</filename> (PO file
for psql) or <filename>fr.mo</filename> (MO file in French).
</para>
<para>
The file format of the PO files is illustrated here:
<programlisting>
# comment
msgid "original string"
msgstr "translated string"
msgid "more original"
msgstr "another translated"
"string can be broken up like this"
...
</programlisting>
The msgid's are extracted from the program source. (They need not
be, but this is the most common way.) The msgstr lines are
initially empty and are filled in with useful strings by the
translator. The strings can contain C-style escape characters and
can be continued across lines as illustrated. (The next line must
start at the beginning of the line.)
</para>
<para>
The # character introduces a comment. If whitespace immediately
follows the # character, then this is a comment maintained by the
translator. There may also be automatic comments, which have a
non-whitespace character immediately following the #. These are
maintained by the various tools that operate on the PO files and
are intended to aid the translator.
<programlisting>
#. automatic comment
#: filename.c:1023
#, flags, flags
</programlisting>
The #. style comments are extracted from the source file where the
message is used. Possibly the programmer has inserted information
for the translator, such as about expected alignment. The #:
comment indicates the exact location(s) where the message is used
in the source. The translator need not look at the program
source, but he can if there is doubt about the correct
translation. The #, comments contain flags that describe the
message in some way. There are currently two flags:
<literal>fuzzy</literal> is set if the message has possibly been
outdated because of changes in the program source. The translator
can then verify this and possibly remove the fuzzy flag. Note
that fuzzy messages are not made available to the end user. The
other flag is <literal>c-format</literal>, which indicates that
the message is a <function>printf</function>-style format
template. This means that the translation should also be a format
string with the same number and type of placeholders. There are
tools that can verify this, which key off the c-format flag.
</para>
</sect2>
<sect2>
<title>Creating and maintaining message catalogs</title>
<para>
Okay, so how does one create a <quote>blank</quote> message
catalog? First, go into the directory that contains the program
whose messages you want to translate. If there is a file
<filename>nls.mk</filename>, then this program has been prepared
for translation.
</para>
<para>
If there are already some <filename>.po</filename> files, then
someone has already done some translation work. The files are
named <filename><replaceable>language</replaceable>.po</filename>,
where <replaceable>language</replaceable> is the <ulink
url="http://lcweb.loc.gov/standards/iso639-2/englangn.html">ISO
639-1</ulink> two-letter language code (in lower case), e.g.,
<filename>fr.po</filename> for French. If there is really a need
for more than one translation effort per language then the files
may also be named
<filename><replaceable>language</replaceable>_<replaceable>region</replaceable>.po</filename>
where <replaceable>region</replaceable> is the <ulink
url="http://www.din.de/gremien/nas/nabd/iso3166ma/codlstp1/en_listp1.html">ISO
3166-1</ulink> two-letter country code (in upper case), e.g.,
<filename>pt_BR.po</filename> for Portuguese in Brazil. If you
find the language you wanted you can just start working on that
file.
</para>
<para>
If you need to start a new translation effort, then first run the
command
<programlisting>
gmake init-po
</programlisting>
This will create a file
<filename><replaceable>progname</replaceable>.pot</filename>.
(<filename>.pot</filename> to distinguish it from PO files that
are <quote>in production</quote>. What does the T stand for? I
don't know.) Copy this file to
<filename><replaceable>language</replaceable>.po</filename> and
edit it. To make it known that the new language is available,
also edit the file <filename>nls.mk</filename> and add the
language (or language and country) code to the line that looks like:
<programlisting>
AVAIL_LANGUAGES := de fr
</programlisting>
(Other languages may appear, of course.)
</para>
<para>
As the underlying program or library changes, messages may be
changed or added by the programmers. In this case you do not need
to start from scratch. Instead, run the command
<programlisting>
gmake update-po
</programlisting>
which will create a new blank message catalog file (the pot file
you started with) and will merge it with the existing PO files.
If the merge algorithm is not sure about a particular message it
marks it <quote>fuzzy</quote> as explained above. For the case
where something went really wrong, the old PO file is saved with a
<filename>.po.old</filename> extension.
</para>
</sect2>
<sect2>
<title>Editing the PO files</title>
<para>
The PO files can be edited with a regular text editor. The
translator should only change the area between the quotes after
the msgstr directive, may add comments and alter the fuzzy flag.
There is (unsurprisingly) a PO mode for Emacs, which I find quite
useful.
</para>
<para>
The PO files need not be completely filled in. The software will
automatically fall back to the original string if no translation
(or an empty translation) is available. It is no problem to
submit incomplete translations for inclusions in the source tree;
that gives room for other people to pick up your work. However,
you are encouraged to give priority to removing fuzzy entries
after doing a merge. Remember that fuzzy entries will not be
installed; they only serve as reference what might be the right
translation.
</para>
<para>
Here are some things to keep in mind while editing the
translations:
<itemizedlist>
<listitem>
<para>
Make sure that if the original ends with a newline, the
translation does, too. Similarly for tabs, etc.
</para>
</listitem>
<listitem>
<para>
If the original is a printf format string, the translation also
needs to be. The translation also needs to have the same
format specifiers in the same order. Sometimes the natural
rules of the language make this impossible or at least awkward.
In this case you can use this format:
<programlisting>
msgstr "Die Datei %2$s hat %1$u Zeichen."
</programlisting>
Then the first placeholder will actually use the second
argument from the list. The
<literal><replaceable>digits</replaceable>$</literal> needs to
follow the % and come before any other format manipulators.
(This feature really exists in the <function>printf</function>
family of functions. You may not have heard of it because
there is little use for it outside of message
internationalization.)
</para>
</listitem>
<listitem>
<para>
If the original string contains a linguistic mistake, report
that (or fix it yourself in the program source) and translate
normally. The corrected string can be merged in when the
program sources have been updated. If the original string
contains a factual mistake, report that (or fix it yourself)
and do not translate it. Instead, you may mark the string with
a comment in the PO file.
</para>
</listitem>
<listitem>
<para>
Maintain the style and tone of the original string.
Specifically, messages that are not sentences (<literal>cannot
open file %s</literal>) should probably not start with a
capital letter (if your language distinguishes letter case) or
end with a period (if your language uses punctuation marks).
</para>
</listitem>
<listitem>
<para>
If you don't know what a message means, or if it is ambiguous,
ask on the developers' mailing list. Chances are that English
speaking end users might also not understand it or find it
ambiguous, so it's best to improve the message.
</para>
</listitem>
</itemizedlist>
</para>
</sect2>
</sect1>
<sect1 id="nls-programmer">
<title>For the Programmer</title>
<para>
This section describes how to support native language support in a
program or library that is part of the PostgreSQL distribution.
Currently, it only applies to C programs.
</para>
<procedure>
<title>Adding NLS support to a program</title>
<step>
<para>
Insert this code into the startup sequence of the program:
<programlisting>
#ifdef ENABLE_NLS
#include &lt;locale.h&gt;
#endif
...
#ifdef ENABLE_NLS
setlocale(LC_ALL, "");
bindtextdomain("<replaceable>progname</replaceable>", LOCALEDIR);
textdomain("<replaceable>progname</replaceable>");
#endif
</programlisting>
(The <replaceable>progname</replaceable> can actually be chosen
freely.)
</para>
</step>
<step>
<para>
Whereever a message that is a candidate for translation is found,
a call to <function>gettext()</function> needs to be inserted. E.g.,
<programlisting>
fprintf(stderr, "panic level %d\n", lvl);
</programlisting>
would be changed to
<programlisting>
fprintf(stderr, gettext("panic level %d\n"), lvl);
</programlisting>
(<symbol>gettext</symbol> is defined as a no-op if no NLS is
configured.)
</para>
<para>
This may tend to add a lot of clutter. One common shortcut is to
<programlisting>
#define _(x) gettext((x))
</programlisting>
Another solution is feasible if the program does much of its
communication through one or a few functions, such as
<function>elog()</function> in the backend. Then you make this
function call <function>gettext</function> internally on all
input values.
</para>
</step>
<step>
<para>
Add a file <filename>nls.mk</filename> in the directory with the
program sources. This file will be read as a makefile. The
following variable assignments need to be made here:
<variablelist>
<varlistentry>
<term>CATALOG_NAME</term>
<listitem>
<para>
The program name, as provided in the
<function>textdomain()</function> call.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>AVAIL_LANGUAGES</term>
<listitem>
<para>
List of provided translations -- empty in the beginning.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>GETTEXT_FILES</term>
<listitem>
<para>
List of files that contain translatable strings, i.e., those
marked with <function>gettext</function> or an alternative
solution. Eventually, this will include nearly all source
files of the program. If this list gets too long you can
make the first <quote>file</quote> be a <literal>+</literal>
and the second word be a file that contains one file name per
line.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>GETTEXT_TRIGGERS</term>
<listitem>
<para>
The tools that generate message catalogs for the translators
to work on need to know what function calls contain
translatable strings. By default, only
<function>gettext()</function> calls are known. If you used
<function>_</function> or other identifiers you need to list
them here. If the translatable string is not the first
argument, the item needs to be of the form
<literal>func:2</literal> (for the second argument).
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</step>
</procedure>
<para>
The build system will automatically take care of building and
installing the message catalogs.
</para>
<para>
To ease the translation of messages, here are some guidelines:
<itemizedlist>
<listitem>
<para>
Do not construct sentences at run-time out of laziness, like
<programlisting>
printf("Files where %s.\n", flag ? "copied" : "removed");
</programlisting>
The word order within the sentence may be different in other
languages.
</para>
</listitem>
<listitem>
<para>
For similar reasons, this won't work:
<programlisting>
printf("copied %d file%s", n, n!=1 ? "s" : "");
</programlisting>
because it assumes how the plural is formed. If you figured you
could solve it like this
<programlisting>
if (n==1)
printf("copied 1 file");
else
printf("copied %d files", n):
</programlisting>
then be disappointed. Some languages have more than two forms,
with some peculiar rules. We may have a solution for this in
the future, but for now this is best avoided altogether. You
could write:
<programlisting>
printf("number of copied files: %d", n);
</programlisting>
</para>
</listitem>
<listitem>
<para>
If you want to communicate something to the translator, such as
about how a message is intended to line up with other output,
precede the occurance of the string with a comment that starts
with <literal>translator</literal>, e.g.,
<programlisting>
/* translator: This message is not what it seems to be. */
</programlisting>
These comments are copied to the message catalog files so that
the translators can see them.
</para>
</listitem>
</itemizedlist>
</para>
</sect1>
</chapter>