[newsfeed] Suppress unsightly animation cases when there are 0 or 1 l…

…ive news items

CHANGELOG.md

@@ -21,6 +21,8 @@ _This release is scheduled to be released on 2024-04-01._
 ### Fixed
 
 - Skip changelog requirement when running tests for dependency updates (#3320)
+- [newsfeed] Suppress unsightly animation cases when there are 0 or 1 active news items
+- [newsfeed] Always compute the feed item URL using the same helper function
 
 ### Deleted
 

modules/default/newsfeed/newsfeed.js

@@ -121,24 +121,30 @@ Module.register("newsfeed", {
 		if (this.activeItem >= this.newsItems.length) {
 			this.activeItem = 0;
 		}
+		this.activeItemCount = this.newsItems.length;
 		// this.config.showFullArticle is a run-time configuration, triggered by optional notifications
 		if (this.config.showFullArticle) {
+			this.activeItemHash = this.newsItems[this.activeItem]?.hash;
 			return {
 				url: this.getActiveItemURL()
 			};
 		}
 		if (this.error) {
+			this.activeItemHash = undefined;
 			return {
 				error: this.error
 			};
 		}
 		if (this.newsItems.length === 0) {
+			this.activeItemHash = undefined;
 			return {
 				empty: true
 			};
 		}
 
 		const item = this.newsItems[this.activeItem];
+		this.activeItemHash = item.hash;
+
 		const items = this.newsItems.map(function (item) {
 			item.publishDate = moment(new Date(item.pubdate)).fromNow();
 			return item;
@@ -312,8 +318,27 @@ Module.register("newsfeed", {
 		if (this.timer) clearInterval(this.timer);
 
 		this.timer = setInterval(() => {
-			this.activeItem++;
-			this.updateDom(this.config.animationSpeed);
+
+			/*
+			 * When animations are enabled, don't update the DOM unless we are actually changing what we are displaying.
+			 * (Animating from a headline to itself is unsightly.)
+			 * Cases:
+			 *
+			 * Number of items | Number of items | Display
+			 * at last update  |   right now     | Behaviour
+			 * ----------------------------------------------------
+			 *     0           |      0          | do not update
+			 *     0           |     >0          | update
+			 *     1           |   0 or >1       | update
+			 *     1           |      1          | update only if item details (hash value) changed
+			 *    >1           |    any          | update
+			 *
+			 * (N.B. We set activeItemCount and activeItemHash in getTemplateData().)
+			 */
+			if (this.newsItems.length !== this.activeItemCount || this.activeItemHash !== this.newsItems[0]?.hash) {
+				this.activeItem++; // this is OK if newsItems.Length==1; getTemplateData will wrap it around
+				this.updateDom(this.config.animationSpeed);
+			}
 
 			// Broadcast NewsFeed if needed
 			if (this.config.broadcastNewsFeeds) {

modules/default/newsfeed/newsfeedfetcher.js

@@ -5,6 +5,7 @@
  * MIT Licensed.
  */
 
+const crypto = require("node:crypto");
 const stream = require("node:stream");
 const FeedMe = require("feedme");
 const iconv = require("iconv-lite");
@@ -67,7 +68,8 @@ const NewsfeedFetcher = function (url, reloadInterval, encoding, logFeedWarnings
 					description: description,
 					pubdate: pubdate,
 					url: url,
-					useCorsProxy: useCorsProxy
+					useCorsProxy: useCorsProxy,
+					hash: crypto.createHash("sha256").update(`${pubdate} :: ${title} :: ${url}`).digest("hex")
 				});
 			} else if (logFeedWarnings) {
 				Log.warn("Can't parse feed item:");