PO4A-RUNTIME

Section: Po4a Tools (7)
Updated: 2019-02-09
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NAME

po4a-runtime - po4a and runtime gettext translation without Autotools

Introduction

With po4a-build, po4a also includes support for adding translation of runtime script output messages using gettext but without requiring the package to adopt Autotools and the typical ./configure process.

Using example Makefile snippets, packages can harness intltool with minimal effort.

Layout

Documentation translation should NOT use the same po/ directory as the runtime translation. Whilst runtime translation can use directories other than po/, it is usually easiest to go with the convention.

Multiple languages

Just a word on packages that use scripts in multiple programming languages. A common mix is Perl and shell. Note bene: gettext WILL get confused and omit strings from one or other language unless file extensions are used for whichever is the least problematic language.

When using multiple languages, experiment with various settings in po/Makevars until you get all the strings you need in the POT file.

In particular, specifying two languages in po/Makevars can be problematic. Instead of:

 # Don't do this:
 XGETTEXT_OPTIONS = -L Perl -L Shell --from-code=iso-8859-1

Consider renaming (or providing symlink(s) for) all files for one of the languages involved and omitting the explicit -L options. The file extension only needs to exist during the time that po/POTFILES.in is being processed.

The --keywords option can also be useful - see the xgettext(1) documentation.

Populating po/

So, create your top level po/ directory and then use the example files in /usr/share/doc/po4a/examples/ to populate it.

LINGUAS

Must exist, even if empty. Consists of a list of translations - each line not starting with a '#' must match an existing PO file. E.g. if LINGUAS contains a single line, 'fr', an fr.po file must exist alongside the LINGUAS file.

 $ cat po/LINGUAS
 cs
 de
 fr
 $

By convention, the LINGUAS file is sorted alphabetically but that is a manual process.

POTFILES.in

The list of files containing the messages that need to be translated at runtime - i.e. your scripts. If you've used the top level po/ directory, the paths should be relative to the top level directory, not the po/ directory itself.

 $ ls -l
 myscript.pl
 another.pl
 foo/support.pl
 po/
 po/POTFILES.in
 $ cat po/POTFILES.in
 myscript.pl
 another.pl
 foo/support.pl
 $

Note that it is explicitly supported that the scripts themselves can contain strings for both runtime and documentation translation, e.g. using gettext functions for runtime and embedded POD content for documentation. So it is not a problem to have the same file listed in po/POTFILES.in and doc/po4a-build.conf

Makevars-perl.example

If your scripts are in Perl, copy this example file as po/Makevars and edit it to suit.

Makevars-shell.example

If your scripts are in shell, copy this example file as po/Makevars and edit it to suit.

po4a-build.make

Copy this example file as po/Makefile - it shouldn't need editing but you may want to keep it updated against /usr/share/doc/po4a/examples/po4a-build.make as it may need to be updated within po4a releases as the underlying intltool support changes. (The file itself was generated from another project using Autotools and intltool.)

Building

These snippets need to be added to your top level Makefile or whatever other method you use to prepare your sources for distribution.

 clean:
        $(MAKE) -C po/ clean

 install:
        $(MAKE) -C po/ install DESTDIR=$(DESTDIR)

 dist:
        $(MAKE) -C po/ pot

(In an Autotools project, this would happen automatically by simply adding po to the "SUBDIRS" value in Makefile.am.)

Maintenance

Runtime translation isn't quite as easy as po4a-build in that adding a new translation does require editing po/LINGUAS, but apart from that, updating translations is merely a case of replacing the relevant PO file with the new version.

Depending on how you prepare your source tarball, you may also need to list new PO files in the MANIFEST file or add to the script(s) that prepare the tarball. (That also applies to po4a-build.)

Any *.mo or *.gmo files in po/ can be deleted / cleaned up.

Copyright

Whilst the example files are part of the po4a project, you are free to use, modify and distribute them in your own projects without needing to refer back to po4a or list the po4a team in your own copyright notices, in the same manner as other build tools like Automake itself. If you want to mention po4a, that is fine too.

AUTHORS

 Neil Williams <linux@codehelp.co.uk>