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

4 files changed, 133 insertions, 0 deletions

diff --git a/data/org.mate.SettingsDaemon.plugins.xsettings.gschema.xml.in b/data/org.mate.SettingsDaemon.plugins.xsettings.gschema.xml.in
index ae4721a..bdba044 100644
--- a/data/org.mate.SettingsDaemon.plugins.xsettings.gschema.xml.in
+++ b/data/org.mate.SettingsDaemon.plugins.xsettings.gschema.xml.in
@@ -10,5 +10,10 @@
       <summary>Priority to use for this plugin</summary>
       <description>Priority to use for this plugin in mate-settings-daemon startup queue</description>
     </key>
+    <key type="a{sv}" name="overrides">
+      <default>{}</default>
+      <summary>A dictionary of XSETTINGS to override</summary>
+      <description>This dictionary maps XSETTINGS names to overrides values. The values must be either strings, signed int32s or (in the case of colors), 4-tuples of uint16 (red, green, blue, alpha; 65535 is fully opaque).</description>
+    </key>
   </schema>
 </schemalist>
diff --git a/plugins/xsettings/msd-xsettings-manager.c b/plugins/xsettings/msd-xsettings-manager.c
index c8199da..ad9bf82 100644
--- a/plugins/xsettings/msd-xsettings-manager.c
+++ b/plugins/xsettings/msd-xsettings-manager.c
@@ -56,6 +56,10 @@
 #define SCALING_FACTOR_QT_KEY "window-scaling-factor-qt-sync"
 
 #define FONT_RENDER_SCHEMA    "org.mate.font-rendering"
+
+#define XSETTINGS_PLUGIN_SCHEMA "org.mate.SettingsDaemon.plugins.xsettings"
+#define XSETTINGS_OVERRIDE_KEY  "overrides"
+
 #define FONT_ANTIALIASING_KEY "antialiasing"
 #define FONT_HINTING_KEY      "hinting"
 #define FONT_RGBA_ORDER_KEY   "rgba-order"
@@ -106,6 +110,7 @@ struct MateXSettingsManagerPrivate
         XSettingsManager **managers;
         GHashTable *gsettings;
         GSettings *gsettings_font;
+        GSettings *plugin_settings;
         fontconfig_monitor_handle_t *fontconfig_handle;
         gint window_scale;
 };
@@ -744,6 +749,34 @@ xft_callback (GSettings            *gsettings G_GNUC_UNUSED,
 }
 
 static void
+override_callback (GSettings            *settings,
+                   const gchar          *key,
+                   MateXSettingsManager *manager)
+{
+        GVariant *value;
+        int i;
+
+        value = g_settings_get_value (settings, XSETTINGS_OVERRIDE_KEY);
+
+        for (i = 0; manager->priv->managers [i]; i++) {
+                xsettings_manager_set_overrides (manager->priv->managers [i], value);
+                xsettings_manager_notify (manager->priv->managers [i]);
+        }
+
+        g_variant_unref (value);
+}
+
+static void
+plugin_callback (GSettings            *settings,
+                 const char           *key,
+                 MateXSettingsManager *manager)
+{
+        if (g_str_equal (key, XSETTINGS_OVERRIDE_KEY)) {
+                override_callback (settings, key, manager);
+        }
+}
+
+static void
 fontconfig_callback (fontconfig_monitor_handle_t *handle,
                      MateXSettingsManager       *manager)
 {
@@ -972,6 +1005,10 @@ mate_xsettings_manager_start (MateXSettingsManager *manager,
         g_signal_connect (manager->priv->gsettings_font, "changed", G_CALLBACK (xft_callback), manager);
         update_xft_settings (manager);
 
+        /* Plugin settings (overrides) */
+        manager->priv->plugin_settings = g_settings_new (XSETTINGS_PLUGIN_SCHEMA);
+        g_signal_connect (manager->priv->plugin_settings, "changed", G_CALLBACK (plugin_callback), manager);
+
         start_fontconfig_monitor (manager);
 
         for (i = 0; manager->priv->managers [i]; i++)
@@ -983,6 +1020,14 @@ mate_xsettings_manager_start (MateXSettingsManager *manager,
                 xsettings_manager_notify (manager->priv->managers [i]);
         }
 
+        /* Load initial overrides */
+        GVariant *overrides = g_settings_get_value (manager->priv->plugin_settings, XSETTINGS_OVERRIDE_KEY);
+        for (i = 0; manager->priv->managers [i]; i++) {
+                xsettings_manager_set_overrides (manager->priv->managers [i], overrides);
+                xsettings_manager_notify (manager->priv->managers [i]);
+        }
+        g_variant_unref (overrides);
+
         mate_settings_profile_end (NULL);
 
         return TRUE;
@@ -1014,6 +1059,11 @@ mate_xsettings_manager_stop (MateXSettingsManager *manager)
                 p->gsettings_font = NULL;
         }
 
+        if (p->plugin_settings != NULL) {
+                g_object_unref (p->plugin_settings);
+                p->plugin_settings = NULL;
+        }
+
         stop_fontconfig_monitor (manager);
 
 }
diff --git a/plugins/xsettings/xsettings-manager.c b/plugins/xsettings/xsettings-manager.c
index 8bf4187..d8f5dd5 100644
--- a/plugins/xsettings/xsettings-manager.c
+++ b/plugins/xsettings/xsettings-manager.c
@@ -26,6 +26,7 @@
 #include <string.h>
 
 #include <X11/Xmd.h>		/* For CARD16 */
+#include <glib.h>
 
 #include "xsettings-manager.h"
 
@@ -44,6 +45,8 @@ struct _XSettingsManager
 
   XSettingsList *settings;
   unsigned long serial;
+
+  GVariant *overrides;
 };
 
 static XSettingsList *settings;
@@ -146,6 +149,7 @@ xsettings_manager_new (Display                *display,
 
   manager->settings = NULL;
   manager->serial = 0;
+  manager->overrides = NULL;
 
   manager->window = XCreateSimpleWindow (display,
 					 RootWindow (display, screen),
@@ -193,6 +197,10 @@ xsettings_manager_destroy (XSettingsManager *manager)
   XDestroyWindow (manager->display, manager->window);
 
   xsettings_list_free (manager->settings);
+
+  if (manager->overrides)
+    g_variant_unref (manager->overrides);
+
   free (manager);
 }
 
@@ -423,3 +431,70 @@ xsettings_manager_notify (XSettingsManager *manager)
   return XSETTINGS_SUCCESS;
 }
 
+#define XSETTINGS_VARIANT_TYPE_COLOR  (G_VARIANT_TYPE ("(qqqq)"))
+
+void
+xsettings_manager_set_overrides (XSettingsManager *manager,
+                                 GVariant         *overrides)
+{
+  GVariantIter iter;
+  const gchar *key;
+  GVariant *value;
+
+  g_return_if_fail (overrides != NULL && g_variant_is_of_type (overrides, G_VARIANT_TYPE_VARDICT));
+
+  if (manager->overrides)
+    {
+      /* unset the existing overrides */
+
+      g_variant_iter_init (&iter, manager->overrides);
+      while (g_variant_iter_next (&iter, "{&sv}", &key, NULL))
+        /* only unset it at this point if it's not in the new list */
+        if (!g_variant_lookup (overrides, key, "*", NULL))
+          xsettings_manager_delete_setting (manager, key);
+      g_variant_unref (manager->overrides);
+    }
+
+  /* save this so we can do the unsets next time */
+  manager->overrides = g_variant_ref_sink (overrides);
+
+  /* set the new values */
+  g_variant_iter_init (&iter, overrides);
+  while (g_variant_iter_loop (&iter, "{&sv}", &key, &value))
+    {
+      XSettingsSetting *setting;
+
+      /* only accept recognised types... */
+      if (!g_variant_is_of_type (value, G_VARIANT_TYPE_STRING) &&
+          !g_variant_is_of_type (value, G_VARIANT_TYPE_INT32) &&
+          !g_variant_is_of_type (value, XSETTINGS_VARIANT_TYPE_COLOR))
+        continue;
+
+      setting = g_new0 (XSettingsSetting, 1);
+      setting->name = g_strdup (key);
+
+      if (g_variant_is_of_type (value, G_VARIANT_TYPE_STRING))
+        {
+          setting->type = XSETTINGS_TYPE_STRING;
+          setting->data.v_string = g_strdup (g_variant_get_string (value, NULL));
+        }
+      else if (g_variant_is_of_type (value, G_VARIANT_TYPE_INT32))
+        {
+          setting->type = XSETTINGS_TYPE_INT;
+          setting->data.v_int = g_variant_get_int32 (value);
+        }
+      else if (g_variant_is_of_type (value, XSETTINGS_VARIANT_TYPE_COLOR))
+        {
+          guint16 red, green, blue, alpha;
+
+          g_variant_get (value, "(qqqq)", &red, &green, &blue, &alpha);
+          setting->type = XSETTINGS_TYPE_COLOR;
+          setting->data.v_color.red = red;
+          setting->data.v_color.green = green;
+          setting->data.v_color.blue = blue;
+          setting->data.v_color.alpha = alpha;
+        }
+
+      xsettings_manager_set_setting (manager, setting);
+    }
+}
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
 }