Added threshold detection when scrolling upwards

... for less jolty upwards scrolling.

public/src/client/topic.js

@@ -141,7 +141,7 @@ define('forum/topic', [
 				return navigator.scrollToPostIndex(postIndex, true);
 			}
 		} else if (bookmark && (!config.usePagination || (config.usePagination && ajaxify.data.pagination.currentPage === 1)) && ajaxify.data.postcount > 5) {
-			navigator.update();
+			navigator.update(0);
 			app.alert({
 				alert_id: 'bookmark',
 				message: '[[topic:bookmark_instructions]]',
@@ -158,7 +158,7 @@ define('forum/topic', [
 				app.removeAlert('bookmark');
 			}, 10000);
 		} else {
-			navigator.update();
+			navigator.update(0);
 		}
 	}
 

public/src/client/topic/posts.js

@@ -218,7 +218,7 @@ define('forum/topic/posts', [
 	};
 
 	Posts.processPage = function(posts) {
-		Posts.unloadImages();
+		Posts.unloadImages(posts);
 		Posts.showBottomPostBar();
 		posts.find('[component="post/content"] img:not(.not-responsive)').addClass('img-responsive');
 		app.createUserTooltips(posts);
@@ -232,8 +232,8 @@ define('forum/topic/posts', [
 		hidePostToolsForDeletedPosts(posts);
 	};
 
-	Posts.unloadImages = function() {
-		var images = components.get('post/content').find('img:not(.not-responsive)');
+	Posts.unloadImages = function(posts) {
+		var images = posts.find('[component="post/content"] img:not(.not-responsive)');
 		images.each(function() {
 			$(this).attr('data-src', $(this).attr('src'));
 			$(this).attr('data-state', 'unloaded');

public/src/modules/navigator.js

@@ -92,12 +92,12 @@ define('navigator', ['forum/pagination', 'components'], function(pagination, com
 	}
 
 	navigator.update = function(threshold) {
-		threshold = typeof threshold === 'number' ? threshold : undefined;
-
 		/*
 			The "threshold" is defined as the distance from the top of the page to
 			a spot where a user is expecting to begin reading.
 		*/
+		threshold = typeof threshold === 'number' ? threshold : undefined;
+
 		var els = $(navigator.selector);
 		if (els.length) {
 			index = parseInt(els.first().attr('data-index'), 10) + 1;
@@ -118,6 +118,15 @@ define('navigator', ['forum/pagination', 'components'], function(pagination, com
 			}
 		});
 
+		// If a threshold is undefined, try to determine one based on new index
+		if (threshold === undefined) {
+			var anchorEl = components.get('post/anchor', index - 1),
+				anchorRect = anchorEl.get(0).getBoundingClientRect();
+
+			threshold = anchorRect.top;
+			console.log('new index', index, anchorEl, threshold);
+		}
+
 		if (typeof navigator.callback === 'function') {
 			navigator.callback(index, count, threshold);
 		}