Allow unstacking mods

osu.Game/Overlays/Mods/ModSelectOverlay.cs

@@ -22,6 +22,7 @@ using osu.Game.Graphics.UserInterface;
 using osu.Game.Input.Bindings;
 using osu.Game.Rulesets.Mods;
 using osu.Game.Screens;
+using osu.Game.Utils;
 using osuTK;
 using osuTK.Graphics;
 using osuTK.Input;
@@ -46,9 +47,27 @@ namespace osu.Game.Overlays.Mods
 
         protected readonly ModSettingsContainer ModSettingsContainer;
 
+        private bool stacked = true;
+
+        /// <summary>
+        /// Whether mod icons should be stacked, or appear as individual buttons.
+        /// </summary>
+        public bool Stacked
+        {
+            get => stacked;
+            set
+            {
+                stacked = value;
+                updateAvailableMods();
+            }
+        }
+
         [NotNull]
         private Func<Mod, bool> isValidMod = m => true;
 
+        /// <summary>
+        /// A function that checks whether a given mod is valid.
+        /// </summary>
         [NotNull]
         public Func<Mod, bool> IsValidMod
         {
@@ -419,11 +438,18 @@ namespace osu.Game.Overlays.Mods
 
         private void updateAvailableMods()
         {
-            if (availableMods.Value == null)
+            if (availableMods?.Value == null)
                 return;
 
             foreach (var section in ModSectionsContainer.Children)
-                section.Mods = availableMods.Value[section.ModType].Where(IsValidMod);
+            {
+                IEnumerable<Mod> modEnumeration = availableMods.Value[section.ModType];
+
+                if (!stacked)
+                    modEnumeration = ModValidation.FlattenMods(modEnumeration);
+
+                section.Mods = modEnumeration.Where(IsValidMod);
+            }
         }
 
         private void selectedModsChanged(ValueChangedEvent<IReadOnlyList<Mod>> mods)

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

@@ -14,6 +14,11 @@ namespace osu.Game.Screens.OnlinePlay.Multiplayer
 {
     public class FreeModSelectOverlay : ModSelectOverlay
     {
+        public FreeModSelectOverlay()
+        {
+            Stacked = false;
+        }
+
         protected override ModSection CreateModSection(ModType type) => new FreeModSection(type);
 
         private class FreeModSection : ModSection

osu.Game/Utils/ModValidation.cs

@@ -42,7 +42,7 @@ namespace osu.Game.Utils
             var incompatibleTypes = new HashSet<Type>();
             var incomingTypes = new HashSet<Type>();
 
-            foreach (var mod in combination.SelectMany(flattenMod))
+            foreach (var mod in combination.SelectMany(FlattenMod))
             {
                 // Add the new mod incompatibilities, checking whether any match the existing mod types.
                 foreach (var t in mod.IncompatibleMods)
@@ -79,7 +79,7 @@ namespace osu.Game.Utils
         {
             var allowedSet = new HashSet<Type>(allowedTypes);
 
-            return combination.SelectMany(flattenMod)
+            return combination.SelectMany(FlattenMod)
                               .All(m => allowedSet.Contains(m.GetType()));
         }
 
@@ -93,20 +93,27 @@ namespace osu.Game.Utils
         /// <param name="incompatibleTypes">The set of incompatible <see cref="Mod"/> types.</param>
         /// <returns>Whether the given <see cref="Mod"/> is incompatible.</returns>
         private static bool isModIncompatible(Mod mod, ICollection<Type> incompatibleTypes)
-            => flattenMod(mod)
+            => FlattenMod(mod)
                .SelectMany(m => m.GetType().EnumerateBaseTypes())
                .Any(incompatibleTypes.Contains);
 
+        /// <summary>
+        /// Flattens a set of <see cref="Mod"/>s, returning a new set with all <see cref="MultiMod"/>s removed.
+        /// </summary>
+        /// <param name="mods">The set of <see cref="Mod"/>s to flatten.</param>
+        /// <returns>The new set, containing all <see cref="Mod"/>s in <paramref name="mods"/> recursively with all <see cref="MultiMod"/>s removed.</returns>
+        public static IEnumerable<Mod> FlattenMods(IEnumerable<Mod> mods) => mods.SelectMany(FlattenMod);
+
         /// <summary>
         /// Flattens a <see cref="Mod"/>, returning a set of <see cref="Mod"/>s in-place of any <see cref="MultiMod"/>s.
         /// </summary>
         /// <param name="mod">The <see cref="Mod"/> to flatten.</param>
         /// <returns>A set of singular "flattened" <see cref="Mod"/>s</returns>
-        private static IEnumerable<Mod> flattenMod(Mod mod)
+        public static IEnumerable<Mod> FlattenMod(Mod mod)
         {
             if (mod is MultiMod multi)
             {
-                foreach (var m in multi.Mods.SelectMany(flattenMod))
+                foreach (var m in multi.Mods.SelectMany(FlattenMod))
                     yield return m;
             }
             else