From d096f2f8f6445eb3524df9612e8d7a891528bebe Mon Sep 17 00:00:00 2001
From: Dean Herbert <pe@ppy.sh>
Date: Mon, 21 Dec 2020 16:39:46 +0900
Subject: [PATCH] Fix potential cross-thread operation during chat channel load

The callbacks are scheduled to the API thread, but hooked up in BDL
load. This causes a potential case of cross-thread collection
enumeration.

I've tested and it seems like the schedule logic should be fine for
short term. Longer term, we probably want to re-think how this works so
background operations aren't performed on the `DrawableChannel` in the
first place (chat shouldn't have an overhead like this when not
visible).

Closes #11231.
---
 osu.Game/Overlays/Chat/DrawableChannel.cs | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/osu.Game/Overlays/Chat/DrawableChannel.cs b/osu.Game/Overlays/Chat/DrawableChannel.cs
index d63faebae4..5926d11c03 100644
--- a/osu.Game/Overlays/Chat/DrawableChannel.cs
+++ b/osu.Game/Overlays/Chat/DrawableChannel.cs
@@ -103,7 +103,7 @@ namespace osu.Game.Overlays.Chat
             Colour = colours.ChatBlue.Lighten(0.7f),
         };
 
-        private void newMessagesArrived(IEnumerable<Message> newMessages)
+        private void newMessagesArrived(IEnumerable<Message> newMessages) => Schedule(() =>
         {
             if (newMessages.Min(m => m.Id) < chatLines.Max(c => c.Message.Id))
             {
@@ -155,9 +155,9 @@ namespace osu.Game.Overlays.Chat
 
             if (shouldScrollToEnd)
                 scrollToEnd();
-        }
+        });
 
-        private void pendingMessageResolved(Message existing, Message updated)
+        private void pendingMessageResolved(Message existing, Message updated) => Schedule(() =>
         {
             var found = chatLines.LastOrDefault(c => c.Message == existing);
 
@@ -169,12 +169,12 @@ namespace osu.Game.Overlays.Chat
                 found.Message = updated;
                 ChatLineFlow.Add(found);
             }
-        }
+        });
 
-        private void messageRemoved(Message removed)
+        private void messageRemoved(Message removed) => Schedule(() =>
         {
             chatLines.FirstOrDefault(c => c.Message == removed)?.FadeColour(Color4.Red, 400).FadeOut(600).Expire();
-        }
+        });
 
         private IEnumerable<ChatLine> chatLines => ChatLineFlow.Children.OfType<ChatLine>();