closes #4772

public/src/client/topic.js

@@ -242,25 +242,29 @@ define('forum/topic', [
 	Topic.navigatorCallback = function(index, elementCount, threshold) {
 		var path = ajaxify.removeRelativePath(window.location.pathname.slice(1));
 		if (!path.startsWith('topic')) {
-			return 1;
+			return;
 		}
 
-		if (!navigator.scrollActive) {
-			var parts = ajaxify.removeRelativePath(window.location.pathname.slice(1)).split('/');
-			var topicId = parts[1],
-				slug = parts[2];
-			var newUrl = 'topic/' + topicId + '/' + (slug ? slug : '');
-			if (index > 1) {
-				newUrl += '/' + index;
+		if (navigator.scrollActive) {
+			return;
 		}
 
 		posts.loadImages(threshold);
 
+		var newUrl = 'topic/' + ajaxify.data.slug + (index > 1 ? ('/' + index) : '');
+
 		if (newUrl !== currentUrl) {
+
 			if (Topic.replaceURLTimeout) {
 				clearTimeout(Topic.replaceURLTimeout);
 			}
+
 			Topic.replaceURLTimeout = setTimeout(function() {
+
+				if (index >= elementCount && app.user.uid) {
+					socket.emit('topics.markAsRead', [ajaxify.data.tid]);
+				}
+
 				updateUserBookmark(index);
 
 				Topic.replaceURLTimeout = 0;
@@ -273,7 +277,6 @@ define('forum/topic', [
 				currentUrl = newUrl;
 			}, 500);
 		}
-		}
 	};
 
 	function updateUserBookmark(index) {

public/src/client/topic/posts.js

@@ -225,9 +225,6 @@ define('forum/topic/posts', [
 			if (data && data.posts && data.posts.length) {
 				createNewPosts(data, replies, direction, done);
 			} else {
-				if (app.user.uid) {
-					socket.emit('topics.markAsRead', [tid]);
-				}
 				navigator.update();
 				done();
 			}

public/src/modules/navigator.js

@@ -17,8 +17,15 @@ define('navigator', ['forum/pagination', 'components'], function(pagination, com
 		navigator.callback = callback;
 		toTop = toTop || function() {};
 		toBottom = toBottom || function() {};
+		var navigatorUpdateTimeoutId = 0;
 
-		$(window).off('scroll', navigator.update).on('scroll', navigator.update);
+		$(window).off('scroll', navigator.update).on('scroll', function() {
+			if (navigatorUpdateTimeoutId) {
+				clearTimeout(navigatorUpdateTimeoutId);
+				navigatorUpdateTimeoutId = 0;
+			}
+			navigatorUpdateTimeoutId = setTimeout(navigator.update, 100);
+		});
 
 		$('.pagination-block .dropdown-menu').off('click').on('click', function(e) {
 			e.stopPropagation();