Make "Sometimes" setting depend on season end date, rather than chance

osu.Game/Configuration/SessionStatics.cs

@@ -1,6 +1,7 @@
 // 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;
 using System.Collections.Generic;
 using osu.Game.Online.API.Requests.Responses;
 
@@ -15,6 +16,7 @@ namespace osu.Game.Configuration
         {
             Set(Static.LoginOverlayDisplayed, false);
             Set(Static.MutedAudioNotificationShownOnce, false);
+            Set(Static.SeasonEndDate, DateTimeOffset.MinValue);
             Set(Static.SeasonalBackgrounds, new List<APISeasonalBackground>());
         }
     }
@@ -23,6 +25,7 @@ namespace osu.Game.Configuration
     {
         LoginOverlayDisplayed,
         MutedAudioNotificationShownOnce,
-        SeasonalBackgrounds
+        SeasonEndDate,
+        SeasonalBackgrounds,
     }
 }

osu.Game/Graphics/Backgrounds/SeasonalBackgroundLoader.cs

@@ -1,6 +1,7 @@
 // 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;
 using System.Collections.Generic;
 using System.Linq;
 using osu.Framework.Allocation;
@@ -18,19 +19,24 @@ namespace osu.Game.Graphics.Backgrounds
     [LongRunningLoad]
     public class SeasonalBackgroundLoader : Component
     {
+        private Bindable<DateTimeOffset> endDate;
         private Bindable<List<APISeasonalBackground>> backgrounds;
         private int current;
 
         [BackgroundDependencyLoader]
         private void load(SessionStatics sessionStatics, IAPIProvider api)
         {
+            endDate = sessionStatics.GetBindable<DateTimeOffset>(Static.SeasonEndDate);
             backgrounds = sessionStatics.GetBindable<List<APISeasonalBackground>>(Static.SeasonalBackgrounds);
+
             if (backgrounds.Value.Any()) return;
 
             var request = new GetSeasonalBackgroundsRequest();
             request.Success += response =>
             {
+                endDate.Value = response.EndDate;
                 backgrounds.Value = response.Backgrounds ?? backgrounds.Value;
+
                 current = RNG.Next(0, backgrounds.Value.Count);
             };
 
@@ -46,6 +52,8 @@ namespace osu.Game.Graphics.Backgrounds
 
             return new SeasonalBackground(url);
         }
+
+        public bool IsInSeason() => DateTimeOffset.Now < endDate.Value;
     }
 
     [LongRunningLoad]

osu.Game/Online/API/Requests/Responses/APISeasonalBackgrounds.cs

@@ -1,6 +1,7 @@
 // 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;
 using System.Collections.Generic;
 using Newtonsoft.Json;
 
@@ -8,6 +9,9 @@ namespace osu.Game.Online.API.Requests.Responses
 {
     public class APISeasonalBackgrounds
     {
+        [JsonProperty("ends_at")]
+        public DateTimeOffset EndDate;
+
         [JsonProperty("backgrounds")]
         public List<APISeasonalBackground> Backgrounds { get; set; }
     }

osu.Game/Screens/Backgrounds/BackgroundScreenDefault.cs

@@ -109,7 +109,7 @@ namespace osu.Game.Screens.Backgrounds
             switch (showSeasonalBackgrounds.Value)
             {
                 case SeasonalBackgrounds.Sometimes:
-                    if (RNG.NextBool())
+                    if (seasonalBackgroundLoader.IsInSeason())
                         goto case SeasonalBackgrounds.Always;
                     break;