Make NavMap objects request sync only on demand

Replaces brute-force sync check loop with a self-listing system where each object is responsible for its own dirty sync, requesting it on demand only.

modules/navigation/nav_link.cpp

@@ -37,6 +37,8 @@ void NavLink::set_map(NavMap *p_map) {
 		return;
 	}
 
+	cancel_sync_request();
+
 	if (map) {
 		map->remove_link(this);
 	}
@@ -46,6 +48,7 @@ void NavLink::set_map(NavMap *p_map) {
 
 	if (map) {
 		map->add_link(this);
+		request_sync();
 	}
 }
 
@@ -57,6 +60,8 @@ void NavLink::set_enabled(bool p_enabled) {
 
 	// TODO: This should not require a full rebuild as the link has not really changed.
 	link_dirty = true;
+
+	request_sync();
 }
 
 void NavLink::set_bidirectional(bool p_bidirectional) {
@@ -65,6 +70,8 @@ void NavLink::set_bidirectional(bool p_bidirectional) {
 	}
 	bidirectional = p_bidirectional;
 	link_dirty = true;
+
+	request_sync();
 }
 
 void NavLink::set_start_position(const Vector3 p_position) {
@@ -73,6 +80,8 @@ void NavLink::set_start_position(const Vector3 p_position) {
 	}
 	start_position = p_position;
 	link_dirty = true;
+
+	request_sync();
 }
 
 void NavLink::set_end_position(const Vector3 p_position) {
@@ -81,11 +90,35 @@ void NavLink::set_end_position(const Vector3 p_position) {
 	}
 	end_position = p_position;
 	link_dirty = true;
+
+	request_sync();
 }
 
-bool NavLink::check_dirty() {
-	const bool was_dirty = link_dirty;
+bool NavLink::is_dirty() const {
+	return link_dirty;
+}
 
+void NavLink::sync() {
 	link_dirty = false;
-	return was_dirty;
+}
+
+void NavLink::request_sync() {
+	if (map && !sync_dirty_request_list_element.in_list()) {
+		map->add_link_sync_dirty_request(&sync_dirty_request_list_element);
+	}
+}
+
+void NavLink::cancel_sync_request() {
+	if (map && sync_dirty_request_list_element.in_list()) {
+		map->remove_link_sync_dirty_request(&sync_dirty_request_list_element);
+	}
+}
+
+NavLink::NavLink() :
+		sync_dirty_request_list_element(this) {
+	type = NavigationUtilities::PathSegmentType::PATH_SEGMENT_TYPE_LINK;
+}
+
+NavLink::~NavLink() {
+	cancel_sync_request();
 }