; * src/pgtkfns.c (parse_resource_key): Use recursive schema lookup
XDG_DATA_DIRS may consist of multiple directories, and
g_settings_schema_source_get_default composes these into a recursive
schema source. One must pass TRUE to g_settings_schema_source_lookup,
otherwise only the first directory in XDG_DATA_DIRS is searched.
It follows that in the case that the directory containing the compiled
GSettings schema for Emacs is not the first in XDG_DATA_DIRS,
parse_resource_key will not accept any resource key, which causes
pgtk_get_defaults_value and pgtk_set_defaults_value to fail.
This impacts systems that compose multiple GSettings schema sources
via XDG_DATA_DIRS, such Flatpak and NixOS.
Supporting GIO documentation for g_settings_schema_source_get_default:
> The returned source may actually consist of multiple schema sources
> from different directories, depending on which directories were given
> in `XDG_DATA_DIRS` and `GSETTINGS_SCHEMA_DIR`. For this reason, all
> lookups performed against the default source should probably be done
> recursively.