Add difficulty application mods

Also fixes circular references when using IJsonSerializable.

osu.Game/Beatmaps/Beatmap.cs

@@ -7,6 +7,7 @@ using osu.Game.Rulesets.Objects;
 using System.Collections.Generic;
 using System.Linq;
 using osu.Game.Beatmaps.ControlPoints;
+using osu.Game.IO.Serialization;
 
 namespace osu.Game.Beatmaps
 {
@@ -45,7 +46,7 @@ namespace osu.Game.Beatmaps
         /// <param name="original">The original beatmap to use the parameters of.</param>
         public Beatmap(Beatmap original = null)
         {
-            BeatmapInfo = original?.BeatmapInfo ?? BeatmapInfo;
+            BeatmapInfo = original?.BeatmapInfo.DeepClone() ?? BeatmapInfo;
             ControlPointInfo = original?.ControlPointInfo ?? ControlPointInfo;
             Breaks = original?.Breaks ?? Breaks;
             ComboColors = original?.ComboColors ?? ComboColors;

osu.Game/Beatmaps/WorkingBeatmap.cs

@@ -52,7 +52,14 @@ namespace osu.Game.Beatmaps
             {
                 lock (beatmapLock)
                 {
-                    return beatmap ?? (beatmap = GetBeatmap());
+                    if (beatmap != null) return beatmap;
+
+                    beatmap = GetBeatmap();
+
+                    // use the database-backed info.
+                    beatmap.BeatmapInfo = BeatmapInfo;
+
+                    return beatmap;
                 }
             }
         }

osu.Game/IO/Serialization/IJsonSerializable.cs

@@ -13,7 +13,7 @@ namespace osu.Game.IO.Serialization
     {
         public static string Serialize(this IJsonSerializable obj)
         {
-            return JsonConvert.SerializeObject(obj);
+            return JsonConvert.SerializeObject(obj, new JsonSerializerSettings { ReferenceLoopHandling = ReferenceLoopHandling.Ignore });
         }
 
         public static T Deserialize<T>(this string objString)

osu.Game/Rulesets/Mods/IApplicableToDifficulty.cs

@@ -0,0 +1,15 @@
+// Copyright (c) 2007-2017 ppy Pty Ltd <contact@ppy.sh>.
+// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
+
+using osu.Game.Beatmaps;
+
+namespace osu.Game.Rulesets.Mods
+{
+    /// <summary>
+    /// An interface for mods that make general adjustments to difficulty.
+    /// </summary>
+    public interface IApplicableToDifficulty
+    {
+        void ApplyToDifficulty(BeatmapDifficulty difficulty);
+    }
+}

osu.Game/Rulesets/Mods/ModEasy.cs

@@ -2,11 +2,12 @@
 // Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
 
 using System;
+using osu.Game.Beatmaps;
 using osu.Game.Graphics;
 
 namespace osu.Game.Rulesets.Mods
 {
-    public abstract class ModEasy : Mod
+    public abstract class ModEasy : Mod, IApplicableToDifficulty
     {
         public override string Name => "Easy";
         public override FontAwesome Icon => FontAwesome.fa_osu_mod_easy;
@@ -15,5 +16,14 @@ namespace osu.Game.Rulesets.Mods
         public override double ScoreMultiplier => 0.5;
         public override bool Ranked => true;
         public override Type[] IncompatibleMods => new[] { typeof(ModHardRock) };
+
+        public void ApplyToDifficulty(BeatmapDifficulty difficulty)
+        {
+            const float ratio = 0.5f;
+            difficulty.CircleSize *= ratio;
+            difficulty.ApproachRate *= ratio;
+            difficulty.DrainRate *= ratio;
+            difficulty.OverallDifficulty *= ratio;
+        }
     }
 }

osu.Game/Rulesets/Mods/ModHardRock.cs

@@ -2,16 +2,26 @@
 // Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
 
 using System;
+using osu.Game.Beatmaps;
 using osu.Game.Graphics;
 
 namespace osu.Game.Rulesets.Mods
 {
-    public abstract class ModHardRock : Mod
+    public abstract class ModHardRock : Mod, IApplicableToDifficulty
     {
         public override string Name => "Hard Rock";
         public override FontAwesome Icon => FontAwesome.fa_osu_mod_hardrock;
         public override ModType Type => ModType.DifficultyIncrease;
         public override string Description => "Everything just got a bit harder...";
         public override Type[] IncompatibleMods => new[] { typeof(ModEasy) };
+
+        public void ApplyToDifficulty(BeatmapDifficulty difficulty)
+        {
+            const float ratio = 1.4f;
+            difficulty.CircleSize *= ratio;
+            difficulty.ApproachRate *= ratio;
+            difficulty.DrainRate *= ratio;
+            difficulty.OverallDifficulty *= ratio;
+        }
     }
 }

osu.Game/Rulesets/UI/HitRenderer.cs

@@ -153,6 +153,10 @@ namespace osu.Game.Rulesets.UI
             // Convert the beatmap
             Beatmap = converter.Convert(beatmap.Beatmap, isForCurrentRuleset);
 
+            // Apply difficulty adjustments from mods before using Difficulty.
+            foreach (var mod in Mods.OfType<IApplicableToDifficulty>())
+                mod.ApplyToDifficulty(Beatmap.BeatmapInfo.Difficulty);
+
             // Apply defaults
             foreach (var h in Beatmap.HitObjects)
                 h.ApplyDefaults(Beatmap.ControlPointInfo, Beatmap.BeatmapInfo.Difficulty);
@@ -163,7 +167,7 @@ namespace osu.Game.Rulesets.UI
             ApplyBeatmap();
 
             // Add mods, should always be the last thing applied to give full control to mods
-            applyMods(beatmap.Mods.Value);
+            applyMods(Mods);
         }
 
         /// <summary>

osu.Game/Screens/Play/Player.cs

@@ -22,6 +22,7 @@ using osu.Game.Rulesets.Mods;
 using osu.Game.Rulesets.Scoring;
 using osu.Game.Screens.Ranking;
 using osu.Framework.Audio.Sample;
+using osu.Game.Beatmaps;
 
 namespace osu.Game.Screens.Play
 {
@@ -77,23 +78,28 @@ namespace osu.Game.Screens.Play
 
             Ruleset rulesetInstance;
 
+            WorkingBeatmap working = Beatmap.Value;
+            Beatmap beatmap;
+
             try
             {
-                if (Beatmap.Value.Beatmap == null)
+                beatmap = working.Beatmap;
+
+                if (beatmap == null)
                     throw new InvalidOperationException("Beatmap was not loaded");
 
-                ruleset = osu?.Ruleset.Value ?? Beatmap.Value.BeatmapInfo.Ruleset;
+                ruleset = osu?.Ruleset.Value ?? beatmap.BeatmapInfo.Ruleset;
                 rulesetInstance = ruleset.CreateInstance();
 
                 try
                 {
-                    HitRenderer = rulesetInstance.CreateHitRendererWith(Beatmap, ruleset.ID == Beatmap.Value.BeatmapInfo.Ruleset.ID);
+                    HitRenderer = rulesetInstance.CreateHitRendererWith(working, ruleset.ID == beatmap.BeatmapInfo.Ruleset.ID);
                 }
                 catch (BeatmapInvalidForRulesetException)
                 {
                     // we may fail to create a HitRenderer if the beatmap cannot be loaded with the user's preferred ruleset
                     // let's try again forcing the beatmap's ruleset.
-                    ruleset = Beatmap.Value.BeatmapInfo.Ruleset;
+                    ruleset = beatmap.BeatmapInfo.Ruleset;
                     rulesetInstance = ruleset.CreateInstance();
                     HitRenderer = rulesetInstance.CreateHitRendererWith(Beatmap, true);
                 }
@@ -110,11 +116,11 @@ namespace osu.Game.Screens.Play
                 return;
             }
 
-            adjustableSourceClock = (IAdjustableClock)Beatmap.Value.Track ?? new StopwatchClock();
+            adjustableSourceClock = (IAdjustableClock)working.Track ?? new StopwatchClock();
             decoupledClock = new DecoupleableInterpolatingFramedClock { IsCoupled = false };
 
             var firstObjectTime = HitRenderer.Objects.First().StartTime;
-            decoupledClock.Seek(Math.Min(0, firstObjectTime - Math.Max(Beatmap.Value.Beatmap.ControlPointInfo.TimingPointAt(firstObjectTime).BeatLength * 4, Beatmap.Value.BeatmapInfo.AudioLeadIn)));
+            decoupledClock.Seek(Math.Min(0, firstObjectTime - Math.Max(beatmap.ControlPointInfo.TimingPointAt(firstObjectTime).BeatLength * 4, beatmap.BeatmapInfo.AudioLeadIn)));
             decoupledClock.ProcessFrame();
 
             offsetClock = new FramedOffsetClock(decoupledClock);
@@ -127,7 +133,7 @@ namespace osu.Game.Screens.Play
             {
                 adjustableSourceClock.Reset();
 
-                foreach (var mod in Beatmap.Value.Mods.Value.OfType<IApplicableToClock>())
+                foreach (var mod in working.Mods.Value.OfType<IApplicableToClock>())
                     mod.ApplyToClock(adjustableSourceClock);
 
                 decoupledClock.ChangeSource(adjustableSourceClock);
@@ -195,7 +201,7 @@ namespace osu.Game.Screens.Play
             hudOverlay.Progress.AllowSeeking = HitRenderer.HasReplayLoaded;
             hudOverlay.Progress.OnSeek = pos => decoupledClock.Seek(pos);
 
-            hudOverlay.ModDisplay.Current.BindTo(Beatmap.Value.Mods);
+            hudOverlay.ModDisplay.Current.BindTo(working.Mods);
 
             //bind HitRenderer to ScoreProcessor and ourselves (for a pass situation)
             HitRenderer.OnAllJudged += onCompletion;

osu.Game/osu.Game.csproj

@@ -117,6 +117,7 @@
     <Compile Include="Overlays\Profile\Sections\RanksSection.cs" />
     <Compile Include="Overlays\Profile\Sections\RecentSection.cs" />
     <Compile Include="Graphics\Containers\ConstrainedIconContainer.cs" />
+    <Compile Include="Rulesets\Mods\IApplicableToDifficulty.cs" />
     <Compile Include="Users\UserCoverBackground.cs" />
     <Compile Include="Overlays\UserProfileOverlay.cs" />
     <Compile Include="Overlays\Profile\ProfileHeader.cs" />