Add "enter" hint to in-gameplay chatbox placeholder text

osu.Game/Localisation/ChatStrings.cs

@@ -24,6 +24,11 @@ public static class ChatStrings
         /// </summary>
         public static LocalisableString MentionUser => new TranslatableString(getKey(@"mention_user"), @"Mention");
 
-        private static string getKey(string key) => $"{prefix}:{key}";
+        /// <summary>
+        /// "press enter to chat..."
+        /// </summary>
+        public static LocalisableString InGameInputPlaceholder => new TranslatableString(getKey(@"in_game_input_placeholder"), @"press enter to chat...");
+
+        private static string getKey(string key) => $@"{prefix}:{key}";
     }
 }

osu.Game/Online/Chat/StandAloneChatDisplay.cs

@@ -128,6 +128,9 @@ private void channelChanged(ValueChangedEvent<Channel> e)
 
         public partial class ChatTextBox : HistoryTextBox
         {
+            public Action Focus;
+            public Action FocusLost;
+
             protected override bool OnKeyDown(KeyDownEvent e)
             {
                 // Chat text boxes are generally used in places where they retain focus, but shouldn't block interaction with other
@@ -153,13 +156,17 @@ protected override void LoadComplete()
                 BackgroundFocused = new Color4(10, 10, 10, 255);
             }
 
+            protected override void OnFocus(FocusEvent e)
+            {
+                base.OnFocus(e);
+                Focus?.Invoke();
+            }
+
             protected override void OnFocusLost(FocusLostEvent e)
             {
                 base.OnFocusLost(e);
                 FocusLost?.Invoke();
             }
-
-            public Action FocusLost;
         }
 
         public partial class StandAloneDrawableChannel : DrawableChannel

osu.Game/Screens/OnlinePlay/Multiplayer/GameplayChatDisplay.cs

@@ -10,6 +10,7 @@
 using osu.Framework.Input.Bindings;
 using osu.Framework.Input.Events;
 using osu.Game.Input.Bindings;
+using osu.Game.Localisation;
 using osu.Game.Online.Rooms;
 using osu.Game.Screens.OnlinePlay.Match.Components;
 using osu.Game.Screens.Play;
@@ -41,7 +42,13 @@ public GameplayChatDisplay(Room room)
 
             Background.Alpha = 0.2f;
 
-            TextBox.FocusLost = () => expandedFromTextBoxFocus.Value = false;
+            TextBox.PlaceholderText = ChatStrings.InGameInputPlaceholder;
+            TextBox.Focus = () => TextBox.PlaceholderText = Resources.Localisation.Web.ChatStrings.InputPlaceholder;
+            TextBox.FocusLost = () =>
+            {
+                TextBox.PlaceholderText = ChatStrings.InGameInputPlaceholder;
+                expandedFromTextBoxFocus.Value = false;
+            };
         }
 
         protected override bool OnHover(HoverEvent e) => true; // use UI mouse cursor.