gdesktopappinfo: add get_string_list() function

The X-Flatpak-RenamedFrom key is used in .desktop files to identify past
names for the desktop file. It is defined to be a list of strings.
However, there was previously no correct way to retrieve a list of
strings from the GKeyFile wrapped by GDesktopAppInfo, short of
re-parsing the file with GKeyFile.

Note that doing something like:

    g_strsplit (g_desktop_app_info_get_string (...), ";", -1)

is not correct: the raw value "a\;b;" represents the one-element list
["a;b"], but g_key_file_get_string() rejects the sequence "\;", and so
g_desktop_app_info_get_string() returns NULL in this case. (Of course, a
.desktop file with a semicolon in its name is a pathological case.)

Add g_desktop_app_info_get_string_list(), a trivial wrapper around
g_key_file_get_string_list(), similar to g_desktop_app_info_get_string()
and co.

The change from g_key_file_free() to g_key_file_unref() in the test is
needed because g_key_file_free() clears the contents of the keyfile.
This is fine for all the fields which are eagerly loaded and copied into
GDesktopAppInfo, but not when we want to access arbitrary stuff from the
keyfile.

docs/reference/gio/gio-sections.txt

@@ -1621,6 +1621,7 @@ g_desktop_app_info_set_desktop_env
 g_desktop_app_info_get_string
 g_desktop_app_info_get_locale_string
 g_desktop_app_info_get_boolean
+g_desktop_app_info_get_string_list
 g_desktop_app_info_has_key
 GDesktopAppLaunchCallback
 g_desktop_app_info_launch_uris_as_manager

gio/gdesktopappinfo.c

@@ -4534,6 +4534,33 @@ g_desktop_app_info_get_boolean (GDesktopAppInfo *info,
                                  G_KEY_FILE_DESKTOP_GROUP, key, NULL);
 }
 
+/**
+ * g_desktop_app_info_get_string_list:
+ * @info: a #GDesktopAppInfo
+ * @key: the key to look up
+ * @length: (out) (optional): return location for the number of returned strings, or %NULL
+ *
+ * Looks up a string list value in the keyfile backing @info.
+ *
+ * The @key is looked up in the "Desktop Entry" group.
+ *
+ * Returns: (array zero-terminated=1 length=length) (element-type utf8) (transfer full):
+ *  a %NULL-terminated string array or %NULL if the specified
+ *  key cannot be found. The array should be freed with g_strfreev().
+ *
+ * Since: 2.59.0
+ */
+gchar **
+g_desktop_app_info_get_string_list (GDesktopAppInfo *info,
+                                    const char      *key,
+                                    gsize           *length)
+{
+  g_return_val_if_fail (G_IS_DESKTOP_APP_INFO (info), NULL);
+
+  return g_key_file_get_string_list (info->keyfile,
+                                     G_KEY_FILE_DESKTOP_GROUP, key, length, NULL);
+}
+
 /**
  * g_desktop_app_info_has_key:
  * @info: a #GDesktopAppInfo

gio/gdesktopappinfo.h

@@ -89,6 +89,11 @@ GLIB_AVAILABLE_IN_2_36
 gboolean         g_desktop_app_info_get_boolean       (GDesktopAppInfo *info,
                                                        const char      *key);
 
+GLIB_AVAILABLE_IN_2_60
+gchar **         g_desktop_app_info_get_string_list (GDesktopAppInfo *info,
+                                                     const char      *key,
+                                                     gsize           *length);
+
 GLIB_AVAILABLE_IN_2_38
 const gchar * const *   g_desktop_app_info_list_actions                 (GDesktopAppInfo   *info);
 

gio/tests/appinfo.c

@@ -512,6 +512,8 @@ test_from_keyfile (void)
   GKeyFile *kf;
   GError *error = NULL;
   const gchar *categories;
+  gchar **categories_list;
+  gsize categories_count;
   gchar **keywords;
   const gchar *file;
   const gchar *name;
@@ -522,7 +524,7 @@ test_from_keyfile (void)
   g_key_file_load_from_file (kf, path, G_KEY_FILE_NONE, &error);
   g_assert_no_error (error);
   info = g_desktop_app_info_new_from_keyfile (kf);
-  g_key_file_free (kf);
+  g_key_file_unref (kf);
   g_assert (info != NULL);
 
   g_object_get (info, "filename", &file, NULL);
@@ -532,6 +534,11 @@ test_from_keyfile (void)
   g_assert (file == NULL);
   categories = g_desktop_app_info_get_categories (info);
   g_assert_cmpstr (categories, ==, "GNOME;GTK;");
+  categories_list = g_desktop_app_info_get_string_list (info, "Categories", &categories_count);
+  g_assert_cmpint (categories_count, ==, 2);
+  g_assert_cmpint (g_strv_length (categories_list), ==, 2);
+  g_assert_cmpstr (categories_list[0], ==, "GNOME");
+  g_assert_cmpstr (categories_list[1], ==, "GTK");
   keywords = (gchar **)g_desktop_app_info_get_keywords (info);
   g_assert_cmpint (g_strv_length (keywords), ==, 2);
   g_assert_cmpstr (keywords[0], ==, "keyword1");
@@ -540,6 +547,7 @@ test_from_keyfile (void)
   g_assert_cmpstr (name, ==, "generic-appinfo-test");
   g_assert (!g_desktop_app_info_get_nodisplay (info));
 
+  g_strfreev (categories_list);
   g_object_unref (info);
 }