From b265888f182935035a372d5f6558f8895b90b2c5 Mon Sep 17 00:00:00 2001
From: Dean Herbert <pe@ppy.sh>
Date: Mon, 16 Jan 2023 19:35:55 +0900
Subject: [PATCH] Add bare minimum touch support to osu! ruleset

---
 osu.Game.Rulesets.Osu/OsuInputManager.cs      | 11 ++-
 .../UI/OsuTouchInputMapper.cs                 | 76 +++++++++++++++++++
 2 files changed, 85 insertions(+), 2 deletions(-)
 create mode 100644 osu.Game.Rulesets.Osu/UI/OsuTouchInputMapper.cs

diff --git a/osu.Game.Rulesets.Osu/OsuInputManager.cs b/osu.Game.Rulesets.Osu/OsuInputManager.cs
index 7dede9e283..28b4f70c10 100644
--- a/osu.Game.Rulesets.Osu/OsuInputManager.cs
+++ b/osu.Game.Rulesets.Osu/OsuInputManager.cs
@@ -1,16 +1,17 @@
 // 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.
 
-#nullable disable
-
 using System.Collections.Generic;
 using System.ComponentModel;
 using System.Linq;
+using osu.Framework.Allocation;
+using osu.Framework.Graphics;
 using osu.Framework.Input;
 using osu.Framework.Input.Bindings;
 using osu.Framework.Input.Events;
 using osu.Framework.Input.StateChanges.Events;
 using osu.Game.Input.Bindings;
+using osu.Game.Rulesets.Osu.UI;
 using osu.Game.Rulesets.UI;
 
 namespace osu.Game.Rulesets.Osu
@@ -45,6 +46,12 @@ namespace osu.Game.Rulesets.Osu
         {
         }
 
+        [BackgroundDependencyLoader]
+        private void load()
+        {
+            Add(new OsuTouchInputMapper(this) { RelativeSizeAxes = Axes.Both });
+        }
+
         protected override bool Handle(UIEvent e)
         {
             if ((e is MouseMoveEvent || e is TouchMoveEvent) && !AllowUserCursorMovement) return false;
diff --git a/osu.Game.Rulesets.Osu/UI/OsuTouchInputMapper.cs b/osu.Game.Rulesets.Osu/UI/OsuTouchInputMapper.cs
new file mode 100644
index 0000000000..f4ed70f790
--- /dev/null
+++ b/osu.Game.Rulesets.Osu/UI/OsuTouchInputMapper.cs
@@ -0,0 +1,76 @@
+// 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.Collections.Generic;
+using System.Linq;
+using osu.Framework.Graphics;
+using osu.Framework.Input;
+using osu.Framework.Input.Events;
+
+namespace osu.Game.Rulesets.Osu.UI
+{
+    public partial class OsuTouchInputMapper : Drawable
+    {
+        /// <summary>
+        /// This is our parent <see cref="osuInputManager"/>.
+        /// </summary>
+        private readonly OsuInputManager osuInputManager;
+
+        /// <summary>
+        /// All the active <see cref="TouchSource"/>s and the <see cref="OsuAction"/> that it triggered (if any).
+        /// Ordered from oldest to newest touch chronologically.
+        /// </summary>
+        private readonly List<TrackedTouch> trackedTouches = new List<TrackedTouch>();
+
+        public OsuTouchInputMapper(OsuInputManager inputManager)
+        {
+            osuInputManager = inputManager;
+        }
+
+        private OsuAction? lastAction;
+
+        protected override bool OnTouchDown(TouchDownEvent e)
+        {
+            OsuAction action = lastAction == OsuAction.LeftButton && trackedTouches.Count > 0 ? OsuAction.RightButton : OsuAction.LeftButton;
+
+            if (trackedTouches.All(t => t.Action != action))
+            {
+                trackedTouches.Add(new TrackedTouch(e.Touch, action));
+                osuInputManager.KeyBindingContainer.TriggerPressed(action);
+                lastAction = action;
+            }
+            else
+            {
+                // Ignore any taps which trigger an action which is already handled. But track them for potential positional input in the future.
+                trackedTouches.Add(new TrackedTouch(e.Touch, null));
+            }
+
+            return true;
+        }
+
+        protected override void OnTouchUp(TouchUpEvent e)
+        {
+            var tracked = trackedTouches.First(t => t.Touch.Source == e.Touch.Source);
+
+            if (tracked.Action is OsuAction action)
+                osuInputManager.KeyBindingContainer.TriggerReleased(action);
+
+            trackedTouches.Remove(tracked);
+
+            base.OnTouchUp(e);
+        }
+
+        private class TrackedTouch
+        {
+            public readonly Touch Touch;
+
+            public readonly OsuAction? Action;
+
+            public TrackedTouch(Touch touch, OsuAction? action)
+            {
+                Touch = touch;
+                Action = action;
+            }
+        }
+    }
+}