glib/docs/reference/glib/i18n.md

Title: Internationalization

# Internationalization

GLib doesn't force any particular localization method upon its users. But
since GLib itself is localized using the `gettext()` mechanism, it seems
natural to offer the de-facto standard `gettext()` support macros in an
easy-to-use form.

In order to use these macros in an application, you must include
`<glib/gi18n.h>`. For use in a library, you must include `<glib/gi18n-lib.h>`
after defining the `GETTEXT_PACKAGE` macro suitably for your library:

```c
#define GETTEXT_PACKAGE "gtk4"
#include <glib/gi18n-lib.h>
```

For an application, note that you also have to call `bindtextdomain()`,
`bind_textdomain_codeset()`, `textdomain()` and `setlocale()` early on in your
`main()` to make `gettext()` work. For example:

```c
#include <glib/gi18n.h>
#include <locale.h>

int
main (int argc, char **argv)
{
  setlocale (LC_ALL, "");
  bindtextdomain (GETTEXT_PACKAGE, DATADIR "/locale");
  bind_textdomain_codeset (GETTEXT_PACKAGE, "UTF-8");
  textdomain (GETTEXT_PACKAGE);

  // Rest of your application.
}
```

where `DATADIR` is as typically provided by Automake or Meson.

For a library, you only have to call `bindtextdomain()` and
`bind_textdomain_codeset()` in your initialization function. If your library
doesn't have an initialization function, you can call the functions before
the first translated message.

The [gettext
manual](http://www.gnu.org/software/gettext/manual/gettext.html#Maintainers)
covers details of how to integrate gettext into a project’s build system and
workflow.

## Macros

GLib provides various convenience C pre-processor macros that make it easy
for tools like [`xgettext`](https://www.gnu.org/software/gettext/manual/html_node/xgettext-Invocation.html)
to extract translatable strings from the source of a library or an
application. These macros are defined when including `<glib/gi18n.h>` or
`<glib/gi18n-lib.h>`.

`_(String)`
:   Marks a string for translation. The string will be replaced by its
    translation at run time, if any exists; otherwise, it will be passed
    as is.


`N_(String)`
:   Marks a string for translation. Unlike `_()`, this macro will not
    replace the string with its translation; this is useful when the
    translatable string is inside a `struct` or array declaration, for
    instance:

        static const char *messages[] = {
          N_("some very meaningful message"),
          N_("and another one"),
        };

    It is the responsibility of the developer to call `gettext()` when
    using the string, e.g.:

        g_print ("%s", idx >= G_N_ELEMENTS (messages)
                 ? _("default message")
                 : gettext (messages[idx]));


`C_(Context, String)`
:   Uses `gettext` to get the translation for `String`. `Context` is
    used as a context. This is mainly useful for short strings which
    may need different translations, depending on the context in which
    they are used. For instance:

        label1 = C_("Navigation", "Back");
        label2 = C_("Body part", "Back");

    If you are using the `C_()` macro, you need to make sure that you
    pass `--keyword=C_:1c,2` to `xgettext` when extracting messages.
    This only works with a version of GNU gettext newer than 0.15.

    This macro is available since GLib 2.16


`NC_(Context, String)`
:   Only marks a string for translation, with context. Similar to `N_()`,
    but allows you to add a context to the translatable string, for
    instance:

        static const char *messages[] = {
          NC_("some context", "some very meaningful message"),
          NC_("some context", "and another one")
        };

    It is the responsibility of the developer to call [func@GLib.dpgettext2]
    when using the string, e.g.:

        g_print ("%s", idx >= G_N_ELEMENTS (messages)
                 ? g_dpgettext2 (NULL, "some context", "a default message")
                 : g_dpgettext2 (NULL, "some context", messages[idx]);

    If you are using the `NC_()` macro, you need to make sure that you pass
    `--keyword=NC_:1c,2` to `xgettext` when extracting messages. This only
    works with a version of GNU gettext newer than 0.15. Intltool has support
    for the `NC_()` macro since version 0.40.1.

    This macro is available since GLib 2.18

`Q_(String)`
:   Like `_()`, but handles context inside the translatable string. This has
    the advantage that the string can be adorned with a prefix to guarantee
    uniqueness and provide context to the translator.

    The `String` is made of two parts, separated by the `|` character. The
    leading part is the prefix, which must not be translated; the trailing
    part is the translatable message.

    One use case given in the gettext manual is GUI translation, where one
    could e.g. disambiguate two ‘Open’ menu entries as `"File|Open"` and
    `"Printer|Open"`. Another use case is the string ‘Russian’ which may
    have to be translated differently depending on whether it’s the name
    of a character set or a language. This could be solved by using
    `"charset|Russian"` and `"language|Russian"`.

    See also the `C_()` macro for a different way to mark up translatable
    strings with context.

    If you are using the `Q_()` macro, you need to make sure that you pass
    `--keyword=Q_` to `xgettext` when extracting messages. If you are using
    a version of GNU gettext newer than 0.15, you can also use `--keyword=Q_:1g`
    to let xgettext split the context string off into a `msgctxt` line in
    the `.po` file.

    This macro is available since GLib 2.4