Merge pull request #12526 from peppy/fix-system-message-ordering

Fix system messages always being displayed above standard messages

osu.Game.Tests/Visual/Online/TestSceneStandAloneChatDisplay.cs

@@ -83,6 +83,28 @@ namespace osu.Game.Tests.Visual.Online
             };
         });
 
+        [Test]
+        public void TestSystemMessageOrdering()
+        {
+            var standardMessage = new Message(messageIdSequence++)
+            {
+                Sender = admin,
+                Content = "I am a wang!"
+            };
+
+            var infoMessage1 = new InfoMessage($"the system is calling {messageIdSequence++}");
+            var infoMessage2 = new InfoMessage($"the system is calling {messageIdSequence++}");
+
+            AddStep("message from admin", () => testChannel.AddNewMessages(standardMessage));
+            AddStep("message from system", () => testChannel.AddNewMessages(infoMessage1));
+            AddStep("message from system", () => testChannel.AddNewMessages(infoMessage2));
+
+            AddAssert("message order is correct", () => testChannel.Messages.Count == 3
+                                                        && testChannel.Messages[0] == standardMessage
+                                                        && testChannel.Messages[1] == infoMessage1
+                                                        && testChannel.Messages[2] == infoMessage2);
+        }
+
         [Test]
         public void TestManyMessages()
         {

osu.Game/Online/Chat/InfoMessage.cs

@@ -8,10 +8,8 @@ namespace osu.Game.Online.Chat
 {
     public class InfoMessage : LocalMessage
     {
-        private static int infoID = -1;
-
         public InfoMessage(string message)
-            : base(infoID--)
+            : base(null)
         {
             Timestamp = DateTimeOffset.Now;
             Content = message;

osu.Game/Online/Chat/Message.cs

@@ -59,7 +59,7 @@ namespace osu.Game.Online.Chat
             return Id.Value.CompareTo(other.Id.Value);
         }
 
-        public virtual bool Equals(Message other) => Id == other?.Id;
+        public virtual bool Equals(Message other) => Id.HasValue && Id == other?.Id;
 
         // ReSharper disable once ImpureMethodCallOnReadonlyValueField
         public override int GetHashCode() => Id.GetHashCode();