-*- coding: utf-8 -*-

Quick start for the localization (l10n) scripts
===============================================

The following assumes that all of these are in present in
$FG_ROOT/Translations:
  - the default translation (default/*.xml);
  - the legacy FlightGear XML localization files (<language_code>/*.xml);
  - except for 'fg-convert-translation-files' which creates them, existing
    XLIFF 1.2 files (<language_code>/FlightGear-nonQt.xlf).

Note: the legacy FlightGear XML localization files are only needed by
      'fg-convert-translation-files' when migrating to the XLIFF format. The
      other scripts only need the default translation and obviously, for
      'fg-update-translation-files', the current XLIFF files[1].


Creating XLIFF files from existing FlightGear legacy XML translation files
--------------------------------------------------------------------------

To get the initial XLIFF files (generated from the default translation in
$FG_ROOT/Translations/default as well as the legacy FlightGear XML
localization files in $FG_ROOT/Translations/<language_code>):

  languages="de en_US es fr it nl pl pt zh_CN"

  # Your shell must expand $languages as several words. POSIX shell does that,
  # but not zsh for instance. Otherwise, don't use a shell variable.
  fg-convert-translation-files --transl-dir="$FG_ROOT/Translations" $languages

  # Add strings found in the default translation but missing in the legacy FG
  # XML l10n files
  fg-update-translation-files --transl-dir="$FG_ROOT/Translations" \
                              merge-new-master $languages

Updating XLIFF files to reflect changes in the default translation
------------------------------------------------------------------

When master strings[2] have changed (in a large sense, i.e.: strings added,
modified or removed, or categories added or removed[3]):

  fg-update-translation-files --transl-dir="$FG_ROOT/Translations" \
                              merge-new-master $languages

Updating XLIFF files to mark or remove obsolete translated strings
------------------------------------------------------------------

To remove unused translated strings (not to be done too often in my opinion):

  fg-update-translation-files --transl-dir="$FG_ROOT/Translations" \
                              remove-unused $languages

(you may replace 'remove-unused' with 'mark-unused' to just mark the strings
as not-to-be-translated, however 'merge-new-master' presented above already
does that)

Merging contents from an XLIFF file into another one
----------------------------------------------------

Suppose a translator has been working on a particular translation file, and
meanwhile the official XLIFF file for this translation has been updated in
FGData (new translatable strings added, obsolete strings marked or removed,
etc.). In such a case, 'fg-merge-xliff-into-xliff' can be used to merge the
translator's work into the project file. Essentially, this means that for all
strings that have the same source text, plural status, number of plural forms
and of course target language, the target texts, “approved” status and
translator comments will be taken from the first file passed in the following
command:

  fg-merge-xliff-into-xliff TRANSLATOR_FILE PROJECT_FILE

Used like this, PROJECT_FILE will be updated with data from TRANSLATOR_FILE.
If you don't want to modify PROJECT_FILE, use the -o (--output) option. If '-'
is passed as argument to this option, then the result is written to the
standard output.

Creating skeleton XLIFF files for new translations
--------------------------------------------------

To create skeleton translations for new languages (e.g., for fr_BE, en_AU and
ca):

  1) Check (add if necessary) that flightgear/meta/i18n.py knows the plural
     forms used in the new languages. This is done by editing PLURAL_FORMS
     towards the top of this i18n.py file (very easy). If the existing entry
     for, e.g., "zh" is sufficient for zh_TW or zh_HK, just let "zh" handle
     them: it will be tried as fallback if there is no perfect match on
     language and territory.

  2) Run a command such as:

       fg-new-translations --transl-dir="$FG_ROOT/Translations" fr_BE en_AU ca

     (if you do this for only one language at a time, you can use the -o
     option to precisely control where the output goes, otherwise
     fg-new-translations chooses an appropriate place based on the value
     specified for --transl-dir)

Getting more information on the scripts
---------------------------------------

fg-convert-translation-files, fg-update-translation-files,
fg-merge-xliff-into-xliff and fg-new-translations all support the --help
option for more detailed information.


Footnotes
---------

  [1] Except for the fg-merge-xliff-into-xliff script, which doesn't have any
      of these requirements.

  [2] Strings in the default translation.

  [3] Only empty categories are removed by this command. An obsolete category
      can be made empty by manual editing (easy, just locate the right
      <group>) or this way:

        fg-update-translation-files --transl-dir=... mark-unused
        fg-update-translation-files --transl-dir=... remove-unused

      (note that this will remove *all* strings marked as unused in the first
      step, not only those in some particular category!)