Gtk.Builder does not localize/translate text

[mazharhussain]

My program’s .ui file

<?xml version="1.0" encoding="UTF-8"?>
<interface>
  <object class="GtkApplicationWindow" id="win">
    <property name="child">
      <object class="GtkLabel">
        <property name="label" translatable="yes">Label</property>
        <property name="height-request">40</property>
      </object>
    </property>
  </object>
</interface>

My program’s .py file

#!/usr/bin/python
import gettext
gettext.install('test-gtk-builder-l10n')

import gi
gi.require_version('Gtk', '4.0')
from gi.repository import Gtk

builder = Gtk.Builder.new_from_file('test-gtk-builder-l10n.ui')
win = builder.get_object('win')
win.set_title(_("Test Gtk.Builder internationalization support"))
app = Gtk.Application(application_id="org.example.l10n.test")
def on_activate(app):
    app.add_window(win)
    win.present()
app.connect('activate', on_activate)
app.run()

Values in my program’s ur.po file

#: ../test-gtk-builder-l10n.py:11
msgid "Test Gtk.Builder internationalization support"
msgstr "وِنڈو ٹائٹل"

#: ../test-gtk-builder-l10n.ui:6
msgid "Label"
msgstr "لیبل"

Result

Actual Question

Why is it that text written directly in python file gets translated but the text in interface definition file does not? Is this a bug in GTK4 or am I doing something wrong?

Note

I also tried settings Gtk.Builder's translation domain and adding _ at the start of translatable text in .ui file. None of these methods worked.

[mcatanzaro (Michael Catanzaro)]

Your application is missing calls to bindtextdomain(), bind_textdomain_codeset(), and textdomain(). These are normally needed at the start of your application.

[mazharhussain]

bind_textdomain_codeset() is deprecated, calling bindtextdomain() and textdomain() does not change the behavior.

I changed the line

gettext.install('test-gtk-builder-l10n')

to

gettext.bindtextdomain('test-gtk-builder-l10n', '/usr/share/locale')
gettext.textdomain('test-gtk-builder-l10n')
_ = gettext.gettext

as suggested by Python’s docs.

Label does not get translated and Window Title still gets translated.

[mcatanzaro (Michael Catanzaro)]

Hmmm… OK sorry, I didn’t read your post closely enough anyway. Try gtk_builder_set_translation_domain(), or alternatively: <interface domain="test-gtk-builder-l10n> in the UI file. Hopefully one of those will work.

[FeRDNYC (Frank Dana)]

I decided to play along at home, and in my testing changing the <interface> tag in the .ui file to <interface domain="test-gtk-builder-l10n"> was enough to enable UI translations… however, the compiled translations also had to be installed as (for this example) /usr/share/locale/ur/LC_MESSAGES/test-gtk-builder-l10n.mo.

I couldn’t find any way to convince Gtk.Builder to load them from a different location, even if I provided a localedir= argument to gettext.install() or gettext.bindtextdomain(). Maybe there’s an environment variable that would’ve worked.