src/js/chat.js

@@ -27,7 +27,7 @@ class Chat extends ElemJS {
 		// connect to the new room's timeline updater
 		if (store.activeRoom.exists()) {
 			const timeline = store.activeRoom.value().timeline
-			const subscription = () => {
+			const beforeChangeSubscription = () => {
 				// scroll anchor does not work if the timeline is scrolled to the top.
 				// at the start, when there are not enough messages for a full screen, this is the case.
 				// once there are enough messages that scrolling is necessary, we initiate a scroll down to activate the scroll anchor.
@@ -40,12 +40,29 @@ class Chat extends ElemJS {
 					}
 				}, 0)
 			}
-			const name = "beforeChange"
-			this.removableSubscriptions.push({name, target: timeline, subscription})
-			timeline.subscribe(name, subscription)
+			this.addSubscription("beforeChange", timeline, beforeChangeSubscription)
+
+			//Make sure after loading scrollback we don't move the scroll position
+			const beforeScrollbackLoadSubscription = () => {
+				const lastScrollHeight = chatMessages.scrollHeight;
+
+				const afterScrollbackLoadSub = () => {
+					const scrollDiff = chatMessages.scrollHeight - lastScrollHeight;
+					chatMessages.scrollTop += scrollDiff;
+
+					timeline.unsubscribe("afterScrollbackLoad", afterScrollbackLoadSub)
+				}
+
+				timeline.subscribe("afterScrollbackLoad", afterScrollbackLoadSub)
+			}
+			this.addSubscription("beforeScrollbackLoad", timeline, beforeScrollbackLoadSubscription)
 		}
 		this.render()
 	}
+	addSubscription(name, target, subscription) {
+		this.removableSubscriptions.push({name, target, subscription})
+		target.subscribe(name, subscription)
+	}
 
 	render() {
 		this.clearChildren()

src/js/timeline.js

@@ -176,12 +176,32 @@ class EventGroup extends ElemJS {
 	}
 }
 
+
+//Displays a spiner and creates an event to notify timeline to load more messages
+class LoadMore extends ElemJS {
+	constructor() {
+		super("div")
+		this.html(`<div class="loading-icon"></div> <span> Loading more... </span>`)
+		const intersection_observer = new IntersectionObserver(e => this.intersectionHandler(e))
+		intersection_observer.observe(this.element)
+
+	}
+
+	intersectionHandler(e) {
+		if (e.some(e => e.isIntersecting)) {
+			const event = new CustomEvent("LoadMore", {bubbles: true})
+			this.element.dispatchEvent(event)
+		}
+	}
+}
+
 class ReactiveTimeline extends ElemJS {
 	constructor(id, list) {
 		super("div")
 		this.class("c-event-groups")
 		this.id = id
 		this.list = list
+		this.load_more = new LoadMore()
 		this.render()
 	}
 
@@ -201,6 +221,9 @@ class ReactiveTimeline extends ElemJS {
 		} else {
 			this.tryAddGroups(event, [search.i])
 		}
+		this.load_more.remove()
+		this.load_more = new LoadMore()
+		this.childAt(0, this.load_more)
 	}
 
 	tryAddGroups(event, indices) {
@@ -233,6 +256,7 @@ class ReactiveTimeline extends ElemJS {
 
 	render() {
 		this.clearChildren()
+		this.child(this.load_more)
 		this.list.forEach(group => this.child(group))
 		this.anchor = new Anchor()
 		this.child(this.anchor)
@@ -244,11 +268,15 @@ class Timeline extends Subscribable {
 		super()
 		Object.assign(this.events, {
 			beforeChange: [],
-			afterChange: []
+			afterChange: [],
+			beforeScrollbackLoad: [],
+			afterScrollbackLoad: [],
 		})
 		Object.assign(this.eventDeps, {
 			beforeChange: [],
-			afterChange: []
+			afterChange: [],
+			beforeScrollbackLoad: [],
+			afterScrollbackLoad: [],
 		})
 		this.room = room
 		this.id = this.room.id
@@ -259,6 +287,8 @@ class Timeline extends Subscribable {
 		this.pending = new Set()
 		this.pendingEdits = []
 		this.from = null
+
+		this.reactiveTimeline.element.addEventListener("LoadMore", () => this.loadScrollback())
 	}
 
 	updateStateEvents(events) {
@@ -343,6 +373,7 @@ class Timeline extends Subscribable {
 	}
 
 	async loadScrollback() {
+		this.broadcast("beforeScrollbackLoad")
 		debug = true
 		if (!this.from) throw new Error("Can't load scrollback, no from token")
 		const url = new URL(`${lsm.get("domain")}/_matrix/client/r0/rooms/${this.id}/messages`)
@@ -356,9 +387,10 @@ class Timeline extends Subscribable {
 		url.searchParams.set("filter", JSON.stringify(filter))
 		const root = await fetch(url.toString()).then(res => res.json())
 		this.from = root.end
-		console.log(this.updateEvents, root.chunk)
+		//console.log(this.updateEvents, root.chunk)
 		if (root.state) this.updateStateEvents(root.state)
 		this.updateEvents(root.chunk)
+		this.broadcast("afterScrollbackLoad")
 	}
 
 	send(body) {
@@ -393,24 +425,24 @@ class Timeline extends Subscribable {
 			this.subscribe("afterChange", subscription)
 		})*/
 	}
-/*
-	getGroupedEvents() {
-		let currentSender = Symbol("N/A")
-		let groups = []
-		let currentGroup = []
-		for (const event of this.list) {
-			if (event.sender === currentSender) {
-				currentGroup.push(event)
-			} else {
-				if (currentGroup.length) groups.push(currentGroup)
-				currentGroup = [event]
-				currentSender = event.sender
+	/*
+		getGroupedEvents() {
+			let currentSender = Symbol("N/A")
+			let groups = []
+			let currentGroup = []
+			for (const event of this.list) {
+				if (event.sender === currentSender) {
+					currentGroup.push(event)
+				} else {
+					if (currentGroup.length) groups.push(currentGroup)
+					currentGroup = [event]
+					currentSender = event.sender
+				}
 			}
+			if (currentGroup.length) groups.push(currentGroup)
+			return groups
 		}
-		if (currentGroup.length) groups.push(currentGroup)
-		return groups
-	}
-	*/
+		*/
 }
 
 module.exports = {Timeline}

src/sass/loading.sass

@@ -0,0 +1,13 @@
+@keyframes spin
+  0%
+    transform: rotate(0deg)
+  100%
+    transform: rotate(180deg)
+
+.loading-icon
+  display: inline-block
+  background-color: #ccc
+  width: 12px
+  height: 12px
+  margin-right: 6px
+  animation: spin 0.7s infinite

src/sass/login.sass

@@ -1,6 +1,8 @@
 @use "./base"
+@use "./loading.sass"
 @use "./colors.sass" as c
 
+
 .main
   justify-content: center
   align-items: center
@@ -41,19 +43,6 @@
 .form-error
   color: red
 
-@keyframes spin
-  0%
-    transform: rotate(0deg)
-  100%
-    transform: rotate(180deg)
-
-.loading-icon
-  display: inline-block
-  background-color: #ccc
-  width: 12px
-  height: 12px
-  margin-right: 6px
-  animation: spin 0.7s infinite
 
 input, button
   font-family: inherit

src/sass/main.sass

@@ -5,3 +5,4 @@
 @use "./components/chat"
 @use "./components/chat-input"
 @use "./components/anchor"
+@use "./loading"