gcharset: Add g_get_language_names_with_category

g_get_language_names() uses LC_MESSAGES and the fallback is useful
for other locale categories too.

https://bugzilla.gnome.org/show_bug.cgi?id=751826

glib/gcharset.c

@@ -18,6 +18,7 @@
 
 #include "config.h"
 
+#include "gcharset.h"
 #include "gcharsetprivate.h"
 
 #include "garray.h"
@@ -553,44 +554,77 @@ language_names_cache_free (gpointer data)
  *    that must not be modified or freed.
  *
  * Since: 2.6
- **/
+ */
 const gchar * const *
 g_get_language_names (void)
 {
-  static GPrivate cache_private = G_PRIVATE_INIT (language_names_cache_free);
-  GLanguageNamesCache *cache = g_private_get (&cache_private);
-  const gchar *value;
+  return g_get_language_names_with_category ("LC_MESSAGES");
+}
+
+/**
+ * g_get_language_names_with_category:
+ * @category_name: a locale category name
+ *
+ * Computes a list of applicable locale names with a locale category name,
+ * which can be used to construct the fallback locale-dependent filenames
+ * or search paths. The returned list is sorted from most desirable to
+ * least desirable and always contains the default locale "C".
+ *
+ * This function consults the environment variables `LANGUAGE`, `LC_ALL`,
+ * @category_name, and `LANG` to find the list of locales specified by the
+ * user.
+ *
+ * g_get_language_names() returns g_get_language_names_with_category("LC_MESSAGES").
+ *
+ * Returns: (array zero-terminated=1) (transfer none): a %NULL-terminated array of strings owned by GLib
+ *    that must not be modified or freed.
+ *
+ * Since: 2.58
+ */
+const gchar * const *
+g_get_language_names_with_category (const gchar *category_name)
+{
+  static GPrivate cache_private = G_PRIVATE_INIT ((void (*)(gpointer)) g_hash_table_remove_all);
+  GHashTable *cache = g_private_get (&cache_private);
+  const gchar *languages;
+  GLanguageNamesCache *name_cache;
+
+  g_return_val_if_fail (category_name != NULL, NULL);
 
   if (!cache)
     {
-      cache = g_new0 (GLanguageNamesCache, 1);
+      cache = g_hash_table_new_full (g_str_hash, g_str_equal,
+                                     g_free, language_names_cache_free);
       g_private_set (&cache_private, cache);
     }
 
-  value = guess_category_value ("LC_MESSAGES");
-  if (!value)
-    value = "C";
+  languages = guess_category_value (category_name);
+  if (!languages)
+    languages = "C";
 
-  if (!(cache->languages && strcmp (cache->languages, value) == 0))
+  name_cache = (GLanguageNamesCache *) g_hash_table_lookup (cache, category_name);
+  if (!(name_cache && name_cache->languages &&
+        strcmp (name_cache->languages, languages) == 0))
     {
       GPtrArray *array;
       gchar **alist, **a;
 
-      g_free (cache->languages);
-      g_strfreev (cache->language_names);
-      cache->languages = g_strdup (value);
+      g_hash_table_remove (cache, category_name);
 
       array = g_ptr_array_sized_new (8);
 
-      alist = g_strsplit (value, ":", 0);
+      alist = g_strsplit (languages, ":", 0);
       for (a = alist; *a; a++)
         append_locale_variants (array, unalias_lang (*a));
       g_strfreev (alist);
       g_ptr_array_add (array, g_strdup ("C"));
       g_ptr_array_add (array, NULL);
 
-      cache->language_names = (gchar **) g_ptr_array_free (array, FALSE);
+      name_cache = g_new0 (GLanguageNamesCache, 1);
+      name_cache->languages = g_strdup (languages);
+      name_cache->language_names = (gchar **) g_ptr_array_free (array, FALSE);
+      g_hash_table_insert (cache, g_strdup (category_name), name_cache);
     }
 
-  return (const gchar * const *) cache->language_names;
+  return (const gchar * const *) name_cache->language_names;
 }

glib/gcharset.h

@@ -34,6 +34,9 @@ gchar *               g_get_codeset         (void);
 
 GLIB_AVAILABLE_IN_ALL
 const gchar * const * g_get_language_names  (void);
+GLIB_AVAILABLE_IN_2_58
+const gchar * const * g_get_language_names_with_category
+                                            (const gchar *category_name);
 GLIB_AVAILABLE_IN_ALL
 gchar **              g_get_locale_variants (const gchar *locale);
 

glib/tests/charset.c

@@ -0,0 +1,75 @@
+/*
+ * Copyright 2018 Red Hat, Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * See the included COPYING file for more information.
+ */
+
+#undef G_DISABLE_ASSERT
+#undef G_LOG_DOMAIN
+
+#include "glib.h"
+
+#define TEST_LOCALE "fr_FR.UTF-8@latin:en_US.UTF-8"
+
+const gchar *TEST_RESULT[] = {
+  "fr_FR.UTF-8@latin",
+  "fr_FR@latin",
+  "fr.UTF-8@latin",
+  "fr@latin",
+  "fr_FR.UTF-8",
+  "fr_FR",
+  "fr.UTF-8",
+  "fr",
+  "en_US.UTF-8",
+  "en_US",
+  "en.UTF-8",
+  "en",
+  "C",
+  NULL
+};
+
+const gchar *TEST_TABLE[] = {
+  "LANGUAGE",
+  "LC_ALL",
+  "LC_CTYPE",
+  "LANG",
+  NULL
+};
+
+static void
+test_language_names_with_category (void)
+{
+  const gchar * const *language_names = NULL;
+  gsize i, j;
+
+  for (i = 0; TEST_TABLE[i]; ++i)
+    {
+      g_test_message ("Test %" G_GSIZE_FORMAT, i);
+      g_assert_true (g_setenv (TEST_TABLE[i], TEST_LOCALE, TRUE));
+      language_names = g_get_language_names_with_category ("LC_CTYPE");
+      g_assert_cmpuint (g_strv_length ((gchar **)language_names), ==, g_strv_length ((gchar **)TEST_RESULT));
+
+      for (j = 0; language_names[j]; ++j)
+        {
+          g_assert_cmpstr (language_names[j], ==, TEST_RESULT[j]);
+        }
+      g_unsetenv (TEST_TABLE[i]);
+    }
+}
+
+int
+main (int argc, char *argv[])
+{
+  g_test_init (&argc, &argv, NULL);
+
+  g_test_bug_base ("http://bugs.gnome.org/");
+
+  g_test_add_func ("/charset/language_names_with_category", test_language_names_with_category);
+
+  return g_test_run ();
+}

glib/tests/meson.build

@@ -6,6 +6,7 @@ glib_tests = [
   'bookmarkfile',
   'bytes',
   'cache',
+  'charset',
   'checksum',
   'collate',
   'cond',