Add and consume multi-lookup API endpoint

osu.Game/Online/API/Requests/GetUsersRequest.cs

@@ -0,0 +1,19 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System.Linq;
+
+namespace osu.Game.Online.API.Requests
+{
+    public class GetUsersRequest : APIRequest<GetUsersResponse>
+    {
+        private readonly int[] userIds;
+
+        public GetUsersRequest(int[] userIds)
+        {
+            this.userIds = userIds;
+        }
+
+        protected override string Target => $@"users/?{userIds.Select(u => $"ids[]={u}&").Aggregate((a, b) => a + b)}";
+    }
+}

osu.Game/Online/API/Requests/GetUsersResponse.cs

@@ -0,0 +1,15 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System.Collections.Generic;
+using Newtonsoft.Json;
+using osu.Game.Users;
+
+namespace osu.Game.Online.API.Requests
+{
+    public class GetUsersResponse : ResponseWithCursor
+    {
+        [JsonProperty("users")]
+        public List<User> Users;
+    }
+}

osu.Game/Overlays/Dashboard/CurrentlyPlayingDisplay.cs

@@ -54,17 +54,18 @@ namespace osu.Game.Overlays.Dashboard
                 switch (e.Action)
                 {
                     case NotifyCollectionChangedAction.Add:
-                        foreach (var u in e.NewItems.OfType<int>())
+                        var request = new GetUsersRequest(e.NewItems.OfType<int>().ToArray());
+
+                        request.Success += users => Schedule(() =>
                         {
-                            var request = new GetUserRequest(u);
+                            foreach (var user in users.Users)
-                            request.Success += user => Schedule(() =>
                             {
                                 if (playingUsers.Contains(user.Id))
                                     userFlow.Add(createUserPanel(user));
-                            });
+                            }
-                            api.Queue(request);
+                        });
-                        }
 
+                        api.Queue(request);
                         break;
 
                     case NotifyCollectionChangedAction.Remove:

osu.Game/Overlays/DashboardOverlay.cs

@@ -131,8 +131,7 @@ namespace osu.Game.Overlays
                     break;
 
                 case DashboardOverlayTabs.CurrentlyPlaying:
-                    //todo: enable once caching logic is better
+                    loadDisplay(new CurrentlyPlayingDisplay());
-                    //loadDisplay(new CurrentlyPlayingDisplay());
                     break;
 
                 default: