xsettings: Add gsettings for custom XSettings overridesxsettings-overrides

Add XSettings override gsettings to allow changing arbitrary XSettings
on GSettings without requiring code changes. This enables third-party
tools (like unity-gtk-module extensions) to integrate with MATE by
setting custom XSettings values at runtime.

The implementation adds an 'overrides' key to the xsettings plugin
schema which accepts a dictionary mapping XSetting names to values.

The complete list of XSettings is over at
https://www.freedesktop.org/wiki/Specifications/XSettingsRegistry/

Backported mostly from:
- https://gitlab.gnome.org/GNOME/gnome-settings-daemon/-/commit/c6e9079d
- https://gitlab.gnome.org/GNOME/gnome-settings-daemon/-/commit/35764838

Fixes: https://github.com/mate-desktop/mate-settings-daemon/issues/158

1 files changed, 3 insertions, 0 deletions

diff --git a/plugins/xsettings/xsettings-manager.h b/plugins/xsettings/xsettings-manager.h
index 55f674b..ebd7740 100644
--- a/plugins/xsettings/xsettings-manager.h
+++ b/plugins/xsettings/xsettings-manager.h
@@ -25,6 +25,7 @@
 #define XSETTINGS_MANAGER_H
 
 #include <X11/Xlib.h>
+#include <glib.h>
 #include "xsettings-common.h"
 
 #ifdef __cplusplus
@@ -62,6 +63,8 @@ XSettingsResult xsettings_manager_set_color      (XSettingsManager       *manage
                                                   const char             *name,
                                                   const XSettingsColor   *value);
 XSettingsResult xsettings_manager_notify         (XSettingsManager *manager);
+void            xsettings_manager_set_overrides  (XSettingsManager *manager,
+                                                  GVariant         *overrides);
 
 #ifdef __cplusplus
 }