From 5bc02cc1c69e104dca9a44439218d77a91d93c55 Mon Sep 17 00:00:00 2001
From: Dean Herbert <pe@ppy.sh>
Date: Mon, 29 Jul 2024 20:25:02 +0900
Subject: [PATCH] Fix background alternating not updating on message removal

---
 osu.Game/Overlays/Chat/ChatLine.cs        |  4 ++++
 osu.Game/Overlays/Chat/DrawableChannel.cs | 23 +++++++++++------------
 2 files changed, 15 insertions(+), 12 deletions(-)

diff --git a/osu.Game/Overlays/Chat/ChatLine.cs b/osu.Game/Overlays/Chat/ChatLine.cs
index e7be7e7814..87e1f5699b 100644
--- a/osu.Game/Overlays/Chat/ChatLine.cs
+++ b/osu.Game/Overlays/Chat/ChatLine.cs
@@ -77,6 +77,9 @@ namespace osu.Game.Overlays.Chat
             get => alternatingBackground;
             set
             {
+                if (alternatingBackground == value)
+                    return;
+
                 alternatingBackground = value;
                 updateBackground();
             }
@@ -122,6 +125,7 @@ namespace osu.Game.Overlays.Chat
                     Masking = true,
                     Blending = BlendingParameters.Additive,
                     CornerRadius = 4,
+                    Alpha = 0,
                     RelativeSizeAxes = Axes.Both,
                     Child = new Box
                     {
diff --git a/osu.Game/Overlays/Chat/DrawableChannel.cs b/osu.Game/Overlays/Chat/DrawableChannel.cs
index f5dd5a24f2..6b3acaa226 100644
--- a/osu.Game/Overlays/Chat/DrawableChannel.cs
+++ b/osu.Game/Overlays/Chat/DrawableChannel.cs
@@ -84,6 +84,17 @@ namespace osu.Game.Overlays.Chat
             highlightedMessage.BindValueChanged(_ => processMessageHighlighting(), true);
         }
 
+        protected override void Update()
+        {
+            base.Update();
+
+            for (int i = 0; i < ChatLineFlow.Count; i++)
+            {
+                if (ChatLineFlow[i] is ChatLine chatline)
+                    chatline.AlternatingBackground = i % 2 == 0;
+            }
+        }
+
         /// <summary>
         /// Processes any pending message in <see cref="highlightedMessage"/>.
         /// </summary>
@@ -104,17 +115,6 @@ namespace osu.Game.Overlays.Chat
             highlightedMessage.Value = null;
         });
 
-        private void updateBackgroundAlternating()
-        {
-            for (int i = 0; i < ChatLineFlow.Count; i++)
-            {
-                if (ChatLineFlow[i] is ChatLine chatline)
-                {
-                    chatline.AlternatingBackground = i % 2 == 0;
-                }
-            }
-        }
-
         protected override void Dispose(bool isDisposing)
         {
             base.Dispose(isDisposing);
@@ -169,7 +169,6 @@ namespace osu.Game.Overlays.Chat
                 scroll.ScrollToEnd();
 
             processMessageHighlighting();
-            updateBackgroundAlternating();
         });
 
         private void pendingMessageResolved(Message existing, Message updated) => Schedule(() =>