Initial implementation of new flow (only working for approach rate)

osu.Game/Rulesets/Mods/DifficultyAdjustSettingsControl.cs

@@ -0,0 +1,97 @@
+// 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 osu.Framework.Allocation;
+using osu.Framework.Bindables;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Containers;
+using osu.Framework.Graphics.UserInterface;
+using osu.Game.Beatmaps;
+using osu.Game.Overlays.Settings;
+
+namespace osu.Game.Rulesets.Mods
+{
+    // TODO: make abstract once we finish making each implementation.
+    public class DifficultyAdjustSettingsControl : SettingsItem<float?>
+    {
+        [Resolved]
+        private IBindable<WorkingBeatmap> beatmap { get; set; }
+
+        protected readonly BindableNumber<float> CurrentNumber = new BindableNumber<float>
+        {
+            // TODO: these need to be pulled out of the main bindable.
+            MinValue = 0,
+            MaxValue = 10,
+        };
+
+        protected override Drawable CreateControl() => new ControlDrawable(CurrentNumber);
+
+        private bool isInternalChange;
+
+        protected override void LoadComplete()
+        {
+            base.LoadComplete();
+
+            beatmap.BindValueChanged(b =>
+            {
+                updateFromDifficulty();
+            }, true);
+
+            Current.BindValueChanged(current =>
+            {
+                if (current.NewValue == null)
+                    updateFromDifficulty();
+            });
+
+            CurrentNumber.BindValueChanged(number =>
+            {
+                if (!isInternalChange)
+                    Current.Value = number.NewValue;
+            });
+        }
+
+        private void updateFromDifficulty()
+        {
+            var difficulty = beatmap.Value.BeatmapInfo.BaseDifficulty;
+
+            if (difficulty == null)
+                return;
+
+            if (Current.Value == null)
+            {
+                isInternalChange = true;
+                CurrentNumber.Value = UpdateFromDifficulty(difficulty);
+                isInternalChange = false;
+            }
+        }
+
+        // TODO: make abstract
+        protected virtual float UpdateFromDifficulty(BeatmapDifficulty difficulty) => 0;
+
+        private class ControlDrawable : CompositeDrawable, IHasCurrentValue<float?>
+        {
+            private readonly BindableWithCurrent<float?> current = new BindableWithCurrent<float?>();
+
+            public Bindable<float?> Current
+            {
+                get => current.Current;
+                set => current.Current = value;
+            }
+
+            public ControlDrawable(BindableNumber<float> currentNumber)
+            {
+                InternalChildren = new Drawable[]
+                {
+                    new SettingsSlider<float>
+                    {
+                        ShowsDefaultIndicator = false,
+                        Current = currentNumber,
+                    }
+                };
+
+                AutoSizeAxes = Axes.Y;
+                RelativeSizeAxes = Axes.X;
+            }
+        }
+    }
+}