Use default system theme if none specified in preferences. Default system theme is now default in juCi++

src/files.h

@@ -13,7 +13,7 @@ const std::string configjson =
 "    },\n"
 "    \"gtk_theme\": {\n"
 "        \"name_comment\": \"Use \\\"\\\" for default theme, At least these two exist on all systems: Adwaita, Raleigh\",\n"
-"        \"name\": \"Adwaita\",\n"
+"        \"name\": \"\",\n"
 "        \"variant_comment\": \"Use \\\"\\\" for default variant, and \\\"dark\\\" for dark theme variant\",\n"
 "        \"variant\": \"\"\n"
 "    },\n"

src/window.cc

@@ -139,11 +139,17 @@ Window::Window() : notebook(Notebook::get()) {
 
 void Window::configure() {
   Config::get().load();
-  auto style_context = Gtk::StyleContext::create();
   auto screen = Gdk::Screen::get_default();
-  auto css_provider = Gtk::CssProvider::get_named(Config::get().window.theme_name, Config::get().window.theme_variant);
+  if(css_provider)
+    Gtk::StyleContext::remove_provider_for_screen(screen, css_provider);
+  if(Config::get().window.theme_name.empty()) {
+    css_provider=Gtk::CssProvider::create();
+    Gtk::Settings::get_default()->property_gtk_application_prefer_dark_theme()=(Config::get().window.theme_variant=="dark");
+  }
+  else
+    css_provider=Gtk::CssProvider::get_named(Config::get().window.theme_name, Config::get().window.theme_variant);
   //TODO: add check if theme exists, or else write error to terminal
-  style_context->add_provider_for_screen(screen, css_provider, GTK_STYLE_PROVIDER_PRIORITY_SETTINGS);
+  Gtk::StyleContext::add_provider_for_screen(screen, css_provider, GTK_STYLE_PROVIDER_PRIORITY_SETTINGS);
   Directories::get().update();
   Menu::get().set_keys();
   Terminal::get().configure();

src/window.h

@@ -29,6 +29,8 @@ private:
   Gtk::HBox info_and_status_hbox;
   Gtk::AboutDialog about;
   
+  Glib::RefPtr<Gtk::CssProvider> css_provider;
+
   void configure();
   void set_menu_actions();
   void activate_menu_items(bool activate=true);