ui: stop polling for single monitor groups

src/plugin.vala

@@ -78,10 +78,9 @@ namespace TunerDisplays {
             page.add_page(monitor_page);
             DisplaysContext.controller.monitor_settings_requested.connect(show_monitor_settings);
 
+            page.notify["list"].connect(setup_single_monitor_groups);
             add_page(page);
-            Idle.add(() => {
-                return setup_single_monitor_groups();
-            });
+            setup_single_monitor_groups();
         }
 
         private void load_css() {
@@ -122,27 +121,25 @@ namespace TunerDisplays {
             single_monitor_context.changed.connect(controller.refresh_from_monitors);
         }
 
-        private bool setup_single_monitor_groups() {
+        private void setup_single_monitor_groups() {
             if (single_monitor_groups_ready)
-                return false;
+                return;
 
             var panel_page = page.list as Tuner.PanelPage;
             if (panel_page == null)
-                return true;
+                return;
 
             var content = panel_page.content;
-            if (content == null)
-                return true;
-
             var panel_content = content as Tuner.PanelContent;
-            if (panel_content == null)
-                return true;
+            if (panel_content == null) {
+                panel_page.notify["content"].connect(setup_single_monitor_groups);
+                return;
+            }
 
             find_single_monitor_groups(panel_content);
             single_monitor_groups_ready = true;
             update_single_monitor_groups();
             DisplaysContext.controller.changed.connect(update_single_monitor_groups);
-            return false;
         }
 
         private void find_single_monitor_groups(Tuner.PanelContent content) {