Use XDG pictures directory as the default media path

If the "Base path for relative media paths" is left empty then
use the XDG pictures directory as the default rather than the home
directory.

This is a better default for our Flatpak distribution.

Fixes #12217.

gramps/gen/const.py

@@ -125,6 +125,10 @@ else:
     USER_CONFIG = os.path.join(GLib.get_user_config_dir(), 'gramps')
     USER_CACHE = os.path.join(GLib.get_user_cache_dir(), 'gramps')
 
+USER_PICTURES = GLib.get_user_special_dir(GLib.UserDirectory.DIRECTORY_PICTURES)
+if not USER_PICTURES:
+    USER_PICTURES = HOME_DIR
+
 VERSION_DIR_NAME = "gramps%s%s" % (VERSION_TUPLE[0], VERSION_TUPLE[1])
 VERSION_DIR = os.path.join(USER_CONFIG, VERSION_DIR_NAME)
 USER_DATA_VERSION = os.path.join(USER_DATA, VERSION_DIR_NAME)

gramps/gen/utils/file.py

@@ -43,7 +43,7 @@ LOG = logging.getLogger(".gen.utils.file")
 #
 #-------------------------------------------------------------------------
 from ..constfunc import win, mac, get_env_var
-from ..const import USER_HOME, ENV, GRAMPS_LOCALE as glocale
+from ..const import USER_HOME, USER_PICTURES, ENV, GRAMPS_LOCALE as glocale
 
 #-------------------------------------------------------------------------
 #
@@ -182,9 +182,9 @@ def expand_media_path(mpath, db):
      - Convert to absolute path
      - Convert slashes and case (on Windows)
     """
-    # Use home dir if no media_path specified
+    # Use XDG pictures diectory if no media_path specified
     if mpath is None:
-        mpath = os.path.abspath(USER_HOME)
+        mpath = os.path.abspath(USER_PICTURES)
     # Expand environment variables
     mpath = expand_path(mpath, False)
     # Relative mediapath are considered as relative to the database

gramps/gen/utils/test/file_test.py

@@ -39,7 +39,7 @@ import unittest
 # Gramps modules
 #
 #-------------------------------------------------------------------------
-from ...const import USER_HOME, USER_PLUGINS, VERSION
+from ...const import USER_HOME, USER_PICTURES, USER_PLUGINS, VERSION
 from ...utils.file import media_path
 from ...db.utils import make_database
 
@@ -66,7 +66,7 @@ class FileTest(unittest.TestCase):
 
             # Test without db.mediapath set
             self.assertEqual(media_path(db), os.path.normcase(os.path.normpath(
-                os.path.abspath(USER_HOME))))
+                os.path.abspath(USER_PICTURES))))
             self.assertTrue(os.path.exists(media_path(db)))
 
             # Test with absolute db.mediapath