Fix TabContainer regressions related to switching tabs in certain cases

Author: YeldhamDev

scene/gui/tab_container.cpp

@@ -147,9 +147,7 @@ void TabContainer::_notification(int p_what) {
 			if (get_tab_count() > 0) {
 				_refresh_tab_names();
 			}
-		} break;
 
-		case NOTIFICATION_POST_ENTER_TREE: {
 			if (setup_current_tab >= -1) {
 				set_current_tab(setup_current_tab);
 				setup_current_tab = -2;
@@ -191,6 +189,25 @@ void TabContainer::_notification(int p_what) {
 			}
 		} break;
 
+		case NOTIFICATION_VISIBILITY_CHANGED: {
+			if (!is_visible() || setup_current_tab > -2) {
+				return;
+			}
+
+			updating_visibility = true;
+
+			// As the visibility change notification will be triggered for all children soon after,
+			// beat it to the punch and make sure that the correct node is the only one visible first.
+			// Otherwise, it can prevent a tab change done right before this container was made visible.
+			Vector<Control *> controls = _get_tab_controls();
+			int current = get_current_tab();
+			for (int i = 0; i < controls.size(); i++) {
+				controls[i]->set_visible(i == current);
+			}
+
+			updating_visibility = false;
+		} break;
+
 		case NOTIFICATION_TRANSLATION_CHANGED:
 		case NOTIFICATION_LAYOUT_DIRECTION_CHANGED:
 		case NOTIFICATION_THEME_CHANGED: {
@@ -611,6 +628,7 @@ void TabContainer::set_current_tab(int p_current) {
 		setup_current_tab = p_current;
 		return;
 	}
+
 	tab_bar->set_current_tab(p_current);
 }