From 1855f48997aad66735b6a90c94ddf49fc8e2d0c8 Mon Sep 17 00:00:00 2001
From: Dean Herbert <pe@ppy.sh>
Date: Wed, 15 Mar 2017 18:07:26 +0900
Subject: [PATCH] Add cancellation support for API requests.

---
 osu.Game/Online/API/APIRequest.cs         | 11 ++++++++++-
 osu.Game/Screens/Select/PlaySongSelect.cs | 10 +++++++---
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/osu.Game/Online/API/APIRequest.cs b/osu.Game/Online/API/APIRequest.cs
index f871e5e20a..43c039eb1e 100644
--- a/osu.Game/Online/API/APIRequest.cs
+++ b/osu.Game/Online/API/APIRequest.cs
@@ -58,8 +58,12 @@ namespace osu.Game.Online.API
         public event APISuccessHandler Success;
         public event APIFailureHandler Failure;
 
+        private bool cancelled;
+
         public void Perform(APIAccess api)
         {
+            if (cancelled) return;
+
             if (startTime == null)
                 startTime = DateTime.Now.TotalMilliseconds();
 
@@ -74,11 +78,16 @@ namespace osu.Game.Online.API
 
             WebRequest.BlockingPerform();
 
-            api.Scheduler.Add(delegate { Success?.Invoke(); });
+            if (WebRequest.Completed)
+                api.Scheduler.Add(delegate { Success?.Invoke(); });
         }
 
+        public void Cancel() => Fail(new OperationCanceledException(@"Request cancelled"));
+
         public void Fail(Exception e)
         {
+            cancelled = true;
+
             WebRequest?.Abort();
             api.Scheduler.Add(delegate
             {
diff --git a/osu.Game/Screens/Select/PlaySongSelect.cs b/osu.Game/Screens/Select/PlaySongSelect.cs
index 97e64f44e2..841f8eda7f 100644
--- a/osu.Game/Screens/Select/PlaySongSelect.cs
+++ b/osu.Game/Screens/Select/PlaySongSelect.cs
@@ -52,19 +52,23 @@ namespace osu.Game.Screens.Select
             }, Key.Number3);
         }
 
+        private GetScoresRequest getScoresRequest;
+
         protected override void OnBeatmapChanged(WorkingBeatmap beatmap)
         {
             beatmap?.Mods.BindTo(modSelect.SelectedMods);
 
             leaderboard.Scores = null;
+            getScoresRequest?.Cancel();
+
             if (beatmap != null)
             {
-                var getScores = new GetScoresRequest(beatmap.BeatmapInfo);
-                getScores.Success += res =>
+                getScoresRequest = new GetScoresRequest(beatmap.BeatmapInfo);
+                getScoresRequest.Success += res =>
                 {
                     leaderboard.Scores = res.Scores;
                 };
-                Game.API.Queue(getScores);
+                Game.API.Queue(getScoresRequest);
             }
 
             base.OnBeatmapChanged(beatmap);