closes #4405

public/src/client/topic.js

@@ -222,10 +222,10 @@ define('forum/topic', [
 
 	function updateTopicTitle() {
 		var span = components.get('navbar/title').find('span');
-		if ($(window).scrollTop() > 50) {
+		if ($(window).scrollTop() > 50 && span.hasClass('hidden')) {
-			span.html(ajaxify.data.title).show();
+			span.html(ajaxify.data.title).removeClass('hidden');
-		} else {
+		} else if ($(window).scrollTop() <= 50 && !span.hasClass('hidden')) {
-			span.html('').hide();
+			span.html('').addClass('hidden');
 		}
 		if ($(window).scrollTop() > 300) {
 			app.removeAlert('bookmark');

public/src/modules/navigator.js

@@ -103,7 +103,10 @@ define('navigator', ['forum/pagination', 'components'], function(pagination, com
 			index = parseInt(els.first().attr('data-index'), 10) + 1;
 		}
 
-		var middleOfViewport = $(window).scrollTop() + $(window).height() / 2;
+		var scrollTop = $(window).scrollTop();
+		var windowHeight = $(window).height();
+		var documentHeight = $(document).height();
+		var middleOfViewport = scrollTop + windowHeight / 2;
 		var previousDistance = Number.MAX_VALUE;
 		els.each(function() {
 			var distanceToMiddle = Math.abs(middleOfViewport - $(this).offset().top);
@@ -118,10 +121,19 @@ define('navigator', ['forum/pagination', 'components'], function(pagination, com
 			}
 		});
 
+
+		// check if we are at the top
+		if (scrollTop === 0 && parseInt(els.first().attr('data-index'), 10) === 0) {
+			index = 1;
+		// check if we are near the bottom
+		} else if (scrollTop + windowHeight > documentHeight - 100 && parseInt(els.last().attr('data-index'), 10) === count - 1) {
+			index = count;
+		}
+
 		// If a threshold is undefined, try to determine one based on new index
 		if (threshold === undefined) {
-			var anchorEl = components.get('post/anchor', index - 1),
+			var anchorEl = components.get('post/anchor', index - 1);
-				anchorRect = anchorEl.get(0).getBoundingClientRect();
+			var anchorRect = anchorEl.get(0).getBoundingClientRect();
 
 			threshold = anchorRect.top;
 		}