Gettext (i18n) ​

Gettext is an i18n tool that is separate from your app's code. The main benefit over other tools is, just as GResource, being integrated with GTK. Gettext apart from basic 1 on 1 translations, is also able to handle plurals and automatically detect the system's language.

You can get the Crystal bindings for it and explore its methods at: https://github.com/GeopJr/gettext.cr.

There are three filetypes associated with it: .pot, .po & .mo. The last one is binary.

Getting Started ​

• Create a po/ folder if you haven't already

• Create a po/LINGUAS file that includes the language codes of the available translations, one per line

• Create a po/POTFILES file that includes the paths of the files we should extract strings from (usually all .ui files, metainfo & desktop)

• Run xgettext to extract the translatable strings into a .pot file, which acts as a "template" for the other translations:

$ xgettext --files-from=po/POTFILES --output=po/APP_ID.pot

$ xgettext --files-from=po/POTFILES --output=po/APP_ID.pot

• Create a .po file for a language using msginit e.g.:

$ msginit -i po/APP_ID.pot -o po/el.po -l el_GR.utf8

$ msginit -i po/APP_ID.pot -o po/el.po -l el_GR.utf8

• Translate the strings found in the newly created .po file

• Create a binary .mo using msgfmt e.g.:

$ msgfmt po/el.po -o po/locale/el/LC_MESSAGES/APP_ID.mo

$ msgfmt po/el.po -o po/locale/el/LC_MESSAGES/APP_ID.mo

• Move the po/locale/ to /usr/share/locale (not necessary)

• Add the following to your prerequisites:

Gettext.setlocale(Gettext::LC::ALL, "")

# The macro allows you to set a custom env var during compile time for the mo location e.g. `MY_APP_LOCALE_LOCATION="./po/locale/"`
Gettext.bindtextdomain("APP_ID", {{env("MY_APP_LOCALE_LOCATION").nil? ? "/usr/share/locale" : env("MY_APP_LOCALE_LOCATION")}})
Gettext.textdomain("APP_ID")

Gettext.setlocale(Gettext::LC::ALL, "")

# The macro allows you to set a custom env var during compile time for the mo location e.g. `MY_APP_LOCALE_LOCATION="./po/locale/"`
Gettext.bindtextdomain("APP_ID", {{env("MY_APP_LOCALE_LOCATION").nil? ? "/usr/share/locale" : env("MY_APP_LOCALE_LOCATION")}})
Gettext.textdomain("APP_ID")

• Test it by running it with LANG="el"

You can also add strings that only exist in code in the .pot (and .po) files and then translate them on demand, for instance:

label = Gtk::Label.new("")
label.text = Gettext.gettext("Hello World")
# LANG="en" => "Hello World"
# LANG="el" => "Γειά σου Κόσμε"

label = Gtk::Label.new("")
label.text = Gettext.gettext("Hello World")
# LANG="en" => "Hello World"
# LANG="el" => "Γειά σου Κόσμε"

Translating .desktop and metainfo files ​

Translating those files is just as easy, for the sake of not replacing themselves, add the .in extension (APP_ID.dekstop.in & APP_ID.metainfo.xml.in).

Now all you have to do is run:

• For the metainfo file:

$ msgfmt --xml --template data/APP_ID.metainfo.xml.in -d "./po" -o data/APP_ID.metainfo.xml

$ msgfmt --xml --template data/APP_ID.metainfo.xml.in -d "./po" -o data/APP_ID.metainfo.xml

• For the .desktop file

$ msgfmt --desktop --template data/APP_ID.desktop.in -d "./po" -o data/APP_ID.desktop

$ msgfmt --desktop --template data/APP_ID.desktop.in -d "./po" -o data/APP_ID.desktop