fix: closes #11731, set postIndex on pagination

public/src/ajaxify.js

@@ -303,11 +303,11 @@ ajaxify.widgets = { render: render };
 			window.scrollTo(0, 0);
 			// if on topic page, scroll to the correct post,
 			// this is here to avoid a flash of the wrong posts at the top of the page
-			if (ajaxify.data.template.topic && ajaxify.data.postIndex > 1) {
-				require(['navigator'], function (navigator) {
+			require(['navigator'], function (navigator) {
+				if (navigator.shouldScrollToPost(ajaxify.data.postIndex)) {
 					navigator.scrollToPostIndex(ajaxify.data.postIndex - 1, true, 0);
-				});
-			}
+				}
+			});
 		}
 		ajaxify.loadScript(tpl_url, function done() {
 			hooks.fire('action:ajaxify.end', { url: url, tpl_url: tpl_url, title: ajaxify.data.title });

public/src/client/topic.js

@@ -151,10 +151,8 @@ define('forum/topic', [
 		const bookmark = ajaxify.data.bookmark || storage.getItem('topic:' + tid + ':bookmark');
 		const postIndex = ajaxify.data.postIndex;
 		updateUserBookmark(postIndex);
-		if (postIndex > 1) {
-			if (components.get('post/anchor', postIndex - 1).length) {
-				return navigator.scrollToPostIndex(postIndex - 1, true, 0);
-			}
+		if (navigator.shouldScrollToPost(postIndex)) {
+			return navigator.scrollToPostIndex(postIndex - 1, true, 0);
 		} else if (bookmark && (
 			!config.usePagination ||
 			(config.usePagination && ajaxify.data.pagination.currentPage === 1)

public/src/modules/navigator.js

@@ -642,6 +642,14 @@ define('navigator', [
 		}
 	};
 
+	navigator.shouldScrollToPost = function (postIndex) {
+		if (!ajaxify.data.template.topic || postIndex <= 1) {
+			return false;
+		}
+		const firstPostEl = $('[component="topic"] [component="post"]').first();
+		return parseInt(firstPostEl.attr('data-index'), 10) !== postIndex - 1;
+	};
+
 	navigator.scrollToPostIndex = function (postIndex, highlight, duration) {
 		const scrollTo = components.get('post', 'index', postIndex);
 		navigator.scrollToElement(scrollTo, highlight, duration, postIndex);

src/controllers/topics.js

@@ -72,8 +72,12 @@ topicsController.get = async function getTopic(req, res, next) {
 	const sort = req.query.sort || settings.topicPostSort;
 	const set = sort === 'most_votes' ? `tid:${tid}:posts:votes` : `tid:${tid}:posts`;
 	const reverse = sort === 'newest_to_oldest' || sort === 'most_votes';
-	if (settings.usePagination && !req.query.page) {
-		currentPage = calculatePageFromIndex(postIndex, settings);
+	if (settings.usePagination) {
+		if (!req.query.page) {
+			currentPage = calculatePageFromIndex(postIndex, settings);
+		} else {
+			postIndex = ((currentPage - 1) * settings.postsPerPage) + 1;
+		}
 	}
 	const { start, stop } = calculateStartStop(currentPage, postIndex, settings);