i18n: Add preset kwarg

Many frameworks, such as glib, provide translation functions and
functions that take format strings. As such every application using
these must duplicate the gettext arguments to function properly.

This reduces that duplication and improves correctness so they are
not left out.

Fixes #1123

mesonbuild/modules/i18n.py

@@ -17,6 +17,32 @@ from .. import coredata, mesonlib, build
 from ..mesonlib import MesonException
 import sys
 
+PRESET_ARGS = {
+    'glib': [
+        '--from-code=UTF-8',
+        '--add-comments',
+
+        # https://developer.gnome.org/glib/stable/glib-I18N.html
+        '--keyword=_',
+        '--keyword=N_',
+        '--keyword=C_:1c,2',
+        '--keyword=NC_:1c,2',
+        '--keyword=g_dcgettext:2',
+        '--keyword=g_dngettext:2,3',
+        '--keyword=g_dpgettext2:2c,3',
+
+        '--flag=N_:1:pass-c-format',
+        '--flag=C_:2:pass-c-format',
+        '--flag=NC_:2:pass-c-format',
+        '--flag=g_dngettext:2:pass-c-format',
+        '--flag=g_strdup_printf:1:c-format',
+        '--flag=g_string_printf:2:c-format',
+        '--flag=g_string_append_printf:2:c-format',
+        '--flag=g_error_new:3:c-format',
+        '--flag=g_set_error:4:c-format',
+    ]
+}
+
 class I18nModule:
 
     def merge_file(self, state, args, kwargs):
@@ -53,6 +79,14 @@ class I18nModule:
         datadirs = mesonlib.stringlistify(kwargs.get('data_dirs', []))
         extra_args = mesonlib.stringlistify(kwargs.get('args', []))
 
+        preset = kwargs.pop('preset', None)
+        if preset:
+            preset_args = PRESET_ARGS.get(preset)
+            if not preset_args:
+                raise coredata.MesonException('i18n: Preset "{}" is not one of the valid options: {}'.format(
+                                              preset, list(PRESET_ARGS.keys())))
+            extra_args = set(preset_args + extra_args)
+
         pkg_arg = '--pkgname=' + packagename
         lang_arg = '--langs=' + '@@'.join(languages)
         datadirs = '--datadirs=' + ':'.join(datadirs) if datadirs else None