mark fragment in storage when start of timeline is reached

so we don't keep looping to fetch more messages
when scrolled all the way up

src/domain/session/room/timeline/TimelineViewModel.js

@@ -1,5 +1,6 @@
 /*
 Copyright 2020 Bruno Windels <bruno@windels.cloud>
+Copyright 2020 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -42,13 +43,16 @@ export class TimelineViewModel {
         this._tiles = new TilesCollection(timeline.entries, tilesCreator({room, ownUserId}));
     }
 
-    // doesn't fill gaps, only loads stored entries/tiles
-    loadAtTop() {
+    /**
+     * @return {bool} startReached if the start of the timeline was reached
+     */
+    async loadAtTop() {
         const firstTile = this._tiles.getFirst();
         if (firstTile.shape === "gap") {
             return firstTile.fill();
         } else {
-            return this._timeline.loadAtTop(50);
+            await this._timeline.loadAtTop(50);
+            return false;
         }
     }
 

src/domain/session/room/timeline/tiles/GapTile.js

@@ -41,6 +41,8 @@ export class GapTile extends SimpleTile {
                 this.emitChange("isLoading");
             }
         }
+        // edgeReached will have been updated by fillGap
+        return this._entry.edgeReached;
     }
 
     updateEntry(entry, params) {

src/matrix/room/Room.js

@@ -83,6 +83,9 @@ export class Room extends EventEmitter {
 
     /** @public */
     async fillGap(fragmentEntry, amount) {
+        if (fragmentEntry.edgeReached) {
+            return;
+        }
         const response = await this._hsApi.messages(this._roomId, {
             from: fragmentEntry.token,
             dir: fragmentEntry.direction.asApiString(),

src/matrix/room/timeline/entries/FragmentBoundaryEntry.js

@@ -60,7 +60,7 @@ export class FragmentBoundaryEntry extends BaseEntry {
     }
 
     get isGap() {
-        return !!this.token;
+        return !!this.token && !this.edgeReached;
     }
 
     get token() {
@@ -79,6 +79,25 @@ export class FragmentBoundaryEntry extends BaseEntry {
         }
     }
 
+    get edgeReached() {
+        if (this.started) {
+            return this.fragment.startReached;
+        } else {
+            return this.fragment.endReached;
+        }
+    }
+
+    set edgeReached(reached) {
+        
+        if (this.started) {
+            this.fragment.startReached = reached;
+        } else {
+            this.fragment.endReached = reached;
+        }
+    }
+
+    
+
     get linkedFragmentId() {
         if (this.started) {
             return this.fragment.previousId;

src/matrix/room/timeline/persistence/GapWriter.js

@@ -178,6 +178,14 @@ export class GapWriter {
         if (fragmentEntry.token !== start) {
             throw new Error("start is not equal to prev_batch or next_batch");
         }
+
+        // begin (or end) of timeline reached
+        if (chunk.length === 0) {
+            fragmentEntry.edgeReached = true;
+            await txn.timelineFragments.update(fragmentEntry.fragment);
+            return {entries: [fragmentEntry], fragments: []};
+        }
+
         // find last event in fragment so we get the eventIndex to begin creating keys at
         let lastKey = await this._findFragmentEdgeEventKey(fragmentEntry, txn);
         // find out if any event in chunk is already present using findFirstOrLastOccurringEventId

src/ui/web/session/room/TimelineList.js

@@ -45,7 +45,10 @@ export class TimelineList extends ListView {
             while (predicate()) {
                 // fill, not enough content to fill timeline
                 this._topLoadingPromise = this._viewModel.loadAtTop();
-                await this._topLoadingPromise;
+                const startReached = await this._topLoadingPromise;
+                if (startReached) {
+                    break;
+                }
             }
         }
         catch (err) {