bug#60565: [PATCH] src/pgtkfns.c (parse_resource_key): Use recursive schema lookup

[Eli Zaretskii <eliz@gnu.org>]

> From: Po Lu <luangruo@yahoo.com>
> Cc: Tad Fisher <tadfisher@gmail.com>,  60565@debbugs.gnu.org
> Date: Sat, 07 Jan 2023 19:04:18 +0800
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> From: Tad Fisher <tadfisher@gmail.com>
> >> Date: Thu, 5 Jan 2023 01:58:47 +0000
> >> 
> >> 
> >> From 8e2cf80593dd78030929f96f0f1a3e1a325428a4 Mon Sep 17 00:00:00 2001
> >> From: Tad Fisher <tadfisher@gmail.com>
> >> Date: Wed, 4 Jan 2023 13:40:17 -0800
> >> Subject: [PATCH] ; * 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.
> >
> > Thanks.  Po Lu, any comments?
> 
> Fine by me.  Please install if the copyright exemption checks out.

It's a single line of code, so the exemption is OK.

Should this go to the release branch?  IOW, is the problem serious
enough and/or was introduced recently enough for us to want it in
Emacs 29?

Thanks.