From a4cd40c2f8874daad21bf07793266ea0e65ad62a Mon Sep 17 00:00:00 2001
From: RMidhunSuresh <hi@midhun.dev>
Date: Fri, 5 Nov 2021 17:25:29 +0530
Subject: [PATCH 1/2] Keep filling gap until sibling changes

---
 .../session/room/timeline/tiles/GapTile.js     | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/src/domain/session/room/timeline/tiles/GapTile.js b/src/domain/session/room/timeline/tiles/GapTile.js
index 1db2100e..2efe9712 100644
--- a/src/domain/session/room/timeline/tiles/GapTile.js
+++ b/src/domain/session/room/timeline/tiles/GapTile.js
@@ -23,6 +23,7 @@ export class GapTile extends SimpleTile {
         this._loading = false;
         this._error = null;
         this._isAtTop = true;
+        this._siblingChanged = false;
     }
 
     async fill() {
@@ -42,11 +43,19 @@ export class GapTile extends SimpleTile {
                 this._loading = false;
                 this.emitChange("isLoading");
             }
+                return true;
         }
+        return false;
     }
 
-    notifyVisible() {
-        this.fill();
+    async notifyVisible() {
+        let depth = 0;
+        let result;
+        do {
+            result = await this.fill();
+            depth = depth + 1;
+        } while (depth < 10 && !this._siblingChanged && result && !this.isDisposed)
+        this._siblingChanged = false;
     }
 
     get isAtTop() {
@@ -60,6 +69,11 @@ export class GapTile extends SimpleTile {
             this._isAtTop = isAtTop;
             this.emitChange("isAtTop");
         }
+        this._siblingChanged = true;
+    }
+
+    updateNextSibling() {
+        this._siblingChanged = true;
     }
 
     updateEntry(entry, params) {

From 781147bf0e453557eb499bc0da238568792b5936 Mon Sep 17 00:00:00 2001
From: Bruno Windels <bruno@windels.cloud>
Date: Fri, 5 Nov 2021 15:42:07 +0100
Subject: [PATCH 2/2] add some comments and rename for clarity

---
 src/domain/session/room/timeline/tiles/GapTile.js | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/src/domain/session/room/timeline/tiles/GapTile.js b/src/domain/session/room/timeline/tiles/GapTile.js
index 2efe9712..c1fed69f 100644
--- a/src/domain/session/room/timeline/tiles/GapTile.js
+++ b/src/domain/session/room/timeline/tiles/GapTile.js
@@ -49,13 +49,15 @@ export class GapTile extends SimpleTile {
     }
 
     async notifyVisible() {
+        // we do (up to 10) backfills while no new tiles have been added to the timeline
+        // because notifyVisible won't be called again until something gets added to the timeline
         let depth = 0;
-        let result;
-        do {
-            result = await this.fill();
-            depth = depth + 1;
-        } while (depth < 10 && !this._siblingChanged && result && !this.isDisposed)
+        let canFillMore;
         this._siblingChanged = false;
+        do {
+            canFillMore = await this.fill();
+            depth = depth + 1;
+        } while (depth < 10 && !this._siblingChanged && canFillMore && !this.isDisposed);
     }
 
     get isAtTop() {
@@ -73,6 +75,9 @@ export class GapTile extends SimpleTile {
     }
 
     updateNextSibling() {
+        // if the sibling of the gap changed while calling room.fill(),
+        // we intepret this as at least one new tile has been added to
+        // the timeline. See notifyVisible why this is important.
         this._siblingChanged = true;
     }