Remember mod selection when re-entering song select

Removes mod application when exiting back to main menu.

Alternative to #1968.
Closes #1961.

osu.Game/OsuGame.cs

@@ -2,6 +2,7 @@
 // Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
 
 using System;
+using System.Collections.Generic;
 using osu.Framework.Configuration;
 using osu.Framework.Screens;
 using osu.Game.Configuration;
@@ -27,6 +28,7 @@ using osu.Game.Overlays.Notifications;
 using osu.Game.Rulesets;
 using osu.Game.Screens.Play;
 using osu.Game.Input.Bindings;
+using osu.Game.Rulesets.Mods;
 using OpenTK.Graphics;
 
 namespace osu.Game
@@ -80,6 +82,9 @@ namespace osu.Game
 
         private SettingsOverlay settings;
 
+        // todo: move this to SongSelect once Screen has the ability to unsuspend.
+        public readonly Bindable<IEnumerable<Mod>> SelectedMods = new Bindable<IEnumerable<Mod>>(new List<Mod>());
+
         public OsuGame(string[] args = null)
         {
             this.args = args;

osu.Game/Overlays/Mods/ModButton.cs

@@ -188,17 +188,19 @@ namespace osu.Game.Overlays.Mods
                 start = Mods.Length - 1;
 
             for (int i = start; i < Mods.Length && i >= 0; i += direction)
-            {
+                if (SelectAt(i)) return;
-                if (Mods[i].HasImplementation)
-                {
-                    changeSelectedIndex(i);
-                    return;
-                }
-            }
 
             Deselect();
         }
 
+        public bool SelectAt(int index)
+        {
+            if (!Mods[index].HasImplementation) return false;
+
+            changeSelectedIndex(index);
+            return true;
+        }
+
         public void Deselect() => changeSelectedIndex(-1);
 
         private void displayMod(Mod mod)

osu.Game/Overlays/Mods/ModSection.cs

@@ -113,6 +113,23 @@ namespace osu.Game.Overlays.Mods
             }
         }
 
+        /// <summary>
+        /// Select one or more mods in this section.
+        /// </summary>
+        /// <param name="mods">The types of <see cref="Mod"/>s which should be deselected.</param>
+        public void SelectTypes(IEnumerable<Mod> mods)
+        {
+            foreach (var button in buttons)
+            {
+                for (int i = 0; i < button.Mods.Length; i++)
+                {
+                    foreach (var mod in mods)
+                        if (mod.GetType().IsInstanceOfType(button.Mods[i]))
+                            button.SelectAt(i);
+                }
+            }
+        }
+
         protected ModSection()
         {
             AutoSizeAxes = Axes.Y;

osu.Game/Overlays/Mods/ModSelectOverlay.cs

@@ -51,6 +51,8 @@ namespace osu.Game.Overlays.Mods
         [BackgroundDependencyLoader(permitNulls: true)]
         private void load(OsuColour colours, OsuGame osu, RulesetStore rulesets)
         {
+            SelectedMods.ValueChanged += selectedModsChanged;
+
             LowMultiplierColour = colours.Red;
             HighMultiplierColour = colours.Green;
 
@@ -63,6 +65,37 @@ namespace osu.Game.Overlays.Mods
             Ruleset.TriggerChange();
         }
 
+        private void selectedModsChanged(IEnumerable<Mod> obj)
+        {
+            foreach (ModSection section in ModSectionsContainer.Children)
+                section.SelectTypes(obj);
+
+            updateMods();
+        }
+
+        private void updateMods()
+        {
+            double multiplier = 1.0;
+            bool ranked = true;
+
+            foreach (Mod mod in SelectedMods.Value)
+            {
+                multiplier *= mod.ScoreMultiplier;
+                ranked &= mod.Ranked;
+            }
+
+            MultiplierLabel.Text = $"{multiplier:N2}x";
+            if (!ranked)
+                MultiplierLabel.Text += " (Unranked)";
+
+            if (multiplier > 1.0)
+                MultiplierLabel.FadeColour(HighMultiplierColour, 200);
+            else if (multiplier < 1.0)
+                MultiplierLabel.FadeColour(LowMultiplierColour, 200);
+            else
+                MultiplierLabel.FadeColour(Color4.White, 200);
+        }
+
         protected override void PopOut()
         {
             base.PopOut();
@@ -97,6 +130,7 @@ namespace osu.Game.Overlays.Mods
         {
             foreach (ModSection section in ModSectionsContainer.Children)
                 section.DeselectAll();
+
             refreshSelectedMods();
         }
 
@@ -119,30 +153,7 @@ namespace osu.Game.Overlays.Mods
             refreshSelectedMods();
         }
 
-        private void refreshSelectedMods()
+        private void refreshSelectedMods() => SelectedMods.Value = ModSectionsContainer.Children.SelectMany(s => s.SelectedMods).ToArray();
-        {
-            SelectedMods.Value = ModSectionsContainer.Children.SelectMany(s => s.SelectedMods).ToArray();
-
-            double multiplier = 1.0;
-            bool ranked = true;
-
-            foreach (Mod mod in SelectedMods.Value)
-            {
-                multiplier *= mod.ScoreMultiplier;
-                ranked &= mod.Ranked;
-            }
-
-            MultiplierLabel.Text = $"{multiplier:N2}x";
-            if (!ranked)
-                MultiplierLabel.Text += " (Unranked)";
-
-            if (multiplier > 1.0)
-                MultiplierLabel.FadeColour(HighMultiplierColour, 200);
-            else if (multiplier < 1.0)
-                MultiplierLabel.FadeColour(LowMultiplierColour, 200);
-            else
-                MultiplierLabel.FadeColour(Color4.White, 200);
-        }
 
         public ModSelectOverlay()
         {

osu.Game/Screens/Select/PlaySongSelect.cs

@@ -13,6 +13,7 @@ using osu.Game.Beatmaps;
 using osu.Game.Graphics;
 using osu.Game.Overlays;
 using osu.Game.Overlays.Mods;
+using osu.Game.Rulesets.Mods;
 using osu.Game.Screens.Edit;
 using osu.Game.Screens.Play;
 using osu.Game.Screens.Ranking;
@@ -47,10 +48,13 @@ namespace osu.Game.Screens.Select
         private SampleChannel sampleConfirm;
 
         [BackgroundDependencyLoader(true)]
-        private void load(OsuColour colours, AudioManager audio, BeatmapManager beatmaps, DialogOverlay dialogOverlay)
+        private void load(OsuColour colours, AudioManager audio, BeatmapManager beatmaps, DialogOverlay dialogOverlay, OsuGame game)
         {
             sampleConfirm = audio.Sample.Get(@"SongSelect/confirm-selection");
 
+            if (game != null)
+                modSelect.SelectedMods.BindTo(game.SelectedMods);
+
             Footer.AddButton(@"mods", colours.Yellow, modSelect, Key.F1, float.MaxValue);
 
             BeatmapOptions.AddButton(@"Remove", @"from unplayed", FontAwesome.fa_times_circle_o, colours.Purple, null, Key.Number1);
@@ -121,6 +125,9 @@ namespace osu.Game.Screens.Select
             if (Beatmap.Value.Track != null)
                 Beatmap.Value.Track.Looping = false;
 
+            Beatmap.Value.Mods.UnbindBindings();
+            Beatmap.Value.Mods.Value = new Mod[] { };
+
             return false;
         }