[gnome-panel] add option to use dark theme variant

[Alberts Muktupāvels <muktupavels src gnome org>]

commit 63bdad08404ace584f6b7a12184293d1dccb691b
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Wed Dec 23 06:10:30 2015 +0200

    add option to use dark theme variant
    
    https://bugzilla.gnome.org/show_bug.cgi?id=759576

 data/org.gnome.gnome-panel.gschema.xml.in.in |    4 ++
 gnome-panel/main.c                           |   43 +++++++++++++++++++++++--
 gnome-panel/panel-enums-gsettings.h          |    6 +++
 gnome-panel/panel-schemas.h                  |    1 +
 4 files changed, 50 insertions(+), 4 deletions(-)
---
diff --git a/data/org.gnome.gnome-panel.gschema.xml.in.in b/data/org.gnome.gnome-panel.gschema.xml.in.in
index 812dd56..813dcb4 100644
--- a/data/org.gnome.gnome-panel.gschema.xml.in.in
+++ b/data/org.gnome.gnome-panel.gschema.xml.in.in
@@ -33,6 +33,10 @@
       <default>'16px'</default>
       <_summary>Icon size for only Applications item in the Menu Bar applet</_summary>
     </key>
+    <key name="theme-variant" enum="org.gnome.gnome-panel.PanelThemeVariant">
+      <default>'system'</default>
+      <_summary>Which theme variant to use</_summary>
+    </key>
   </schema>
 
   <schema id="org.gnome.gnome-panel.layout" path="/org/gnome/gnome-panel/layout/">
diff --git a/gnome-panel/main.c b/gnome-panel/main.c
index acae6d5..683ad04 100644
--- a/gnome-panel/main.c
+++ b/gnome-panel/main.c
@@ -23,6 +23,7 @@
 #include "panel-action-protocol.h"
 #include "panel-icon-names.h"
 #include "panel-layout.h"
+#include "panel-schemas.h"
 #include "xstuff.h"
 
 /* globals */
@@ -31,6 +32,9 @@ GSList *panel_list = NULL;
 
 static gboolean  replace = FALSE;
 static gboolean  version = FALSE;
+
+static GSettings *g_settings = NULL;
+static GtkSettings *gtk_settings = NULL;
 static GtkStyleProvider *provider = NULL;
 
 static const GOptionEntry options[] = {
@@ -85,6 +89,29 @@ theme_changed (GtkSettings *settings,
   g_free (resource);
 }
 
+static void
+theme_variant_changed_cb (GSettings   *settings,
+                          const gchar *key,
+                          gpointer     user_data)
+{
+  PanelThemeVariant variant;
+
+  variant = g_settings_get_enum (settings, key);
+
+  if (variant == PANEL_THEME_VARIANT_SYSTEM)
+    {
+      gtk_settings_reset_property (gtk_settings,
+                                   "gtk-application-prefer-dark-theme");
+    }
+  else
+    {
+      g_object_set (gtk_settings, "gtk-application-prefer-dark-theme",
+                    variant == PANEL_THEME_VARIANT_DARK, NULL);
+    }
+
+  theme_changed (gtk_settings, NULL);
+}
+
 static gboolean
 on_term_signal (gpointer user_data)
 {
@@ -104,7 +131,6 @@ main (int argc, char **argv)
 {
        GOptionContext *context;
        GError         *error;
-       GtkSettings    *settings;
        PanelSession   *session;
        GSList         *toplevels_to_destroy;
        GSList         *l;
@@ -165,12 +191,21 @@ main (int argc, char **argv)
         * connecting to the session manager */
        panel_session_register_client (session);
 
-       settings = gtk_settings_get_default ();
-       g_signal_connect (settings, "notify::gtk-theme-name", G_CALLBACK (theme_changed), NULL);
-       theme_changed (settings, NULL);
+       g_settings = g_settings_new (PANEL_GENERAL_SCHEMA);
+       g_signal_connect (g_settings, "changed::" PANEL_GENERAL_THEME_VARIANT_KEY,
+                         G_CALLBACK (theme_variant_changed_cb), NULL);
+
+       gtk_settings = gtk_settings_get_default ();
+       g_signal_connect (gtk_settings, "notify::gtk-theme-name",
+                         G_CALLBACK (theme_changed), NULL);
+       g_signal_connect (gtk_settings, "notify::gtk-application-prefer-dark-theme",
+                         G_CALLBACK (theme_changed), NULL);
+
+       theme_variant_changed_cb (g_settings, PANEL_GENERAL_THEME_VARIANT_KEY, NULL);
 
        gtk_main ();
 
+       g_object_unref (g_settings);
        g_object_unref (session);
 
        toplevels_to_destroy = g_slist_copy (panel_toplevel_list_toplevels ());
diff --git a/gnome-panel/panel-enums-gsettings.h b/gnome-panel/panel-enums-gsettings.h
index a8aee26..0c9f3c3 100644
--- a/gnome-panel/panel-enums-gsettings.h
+++ b/gnome-panel/panel-enums-gsettings.h
@@ -58,6 +58,12 @@ typedef enum {
        PANEL_BACKGROUND_IMAGE_STYLE_FIT     = 2
 } PanelBackgroundImageStyle;
 
+typedef enum {
+       PANEL_THEME_VARIANT_SYSTEM,
+       PANEL_THEME_VARIANT_LIGHT,
+       PANEL_THEME_VARIANT_DARK
+} PanelThemeVariant;
+
 G_END_DECLS
 
 #endif /* __PANEL_ENUMS_GSETTINGS_H__ */
diff --git a/gnome-panel/panel-schemas.h b/gnome-panel/panel-schemas.h
index ba6962d..0a3d495 100644
--- a/gnome-panel/panel-schemas.h
+++ b/gnome-panel/panel-schemas.h
@@ -6,6 +6,7 @@
 #define PANEL_GENERAL_SCHEMA                    "org.gnome.gnome-panel.general"
 #define PANEL_GENERAL_CONFIRM_PANEL_REMOVAL_KEY "confirm-panel-removal"
 #define PANEL_GENERAL_ENABLE_TOOLTIPS_KEY       "enable-tooltips"
+#define PANEL_GENERAL_THEME_VARIANT_KEY         "theme-variant"
 
 #define PANEL_LOCKDOWN_SCHEMA                 "org.gnome.gnome-panel.lockdown"
 #define PANEL_LOCKDOWN_COMPLETE_LOCKDOWN_KEY  "locked-down"