Fix hovering with tablet causing mouse buttons to be immediately released (#6701)

* Fix LMB hold when hovering with tablet pen

Fixes an issue where LMB would be released immediately when the pen is in hover range.
Added pen pressure hysteresis, may be needed.

* Fix LMB hold when hovering with tablet pen

Fixes an issue where LMB would be released immediately when the pen is in hover range.
Added pen pressure hysteresis, may be needed.

* Fix LMB hold when hovering with tablet pen

Stop continuously propagating pen LMB state; use edge-only press/release with a small internal hysteresis and release on tablet disconnect.

* Fix LMB hold when hovering with tablet pen

* Fix LMB hold when hovering with tablet pen

* Rewrite for simplicity

---------

Co-authored-by: Dean Herbert <pe@ppy.sh>

Author: YNataniel295

osu.Framework/Input/Handlers/Tablet/OpenTabletDriverHandler.cs

@@ -1,6 +1,7 @@
 // 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;
 using System.Collections.Generic;
 using System.Linq;
 using System.Threading.Tasks;
@@ -44,7 +45,7 @@ public class OpenTabletDriverHandler : InputHandler, IAbsolutePointer, IRelative
 
         public Bindable<float> Rotation { get; } = new Bindable<float>();
 
-        public BindableFloat PressureThreshold { get; } = new BindableFloat(0.0f)
+        public BindableFloat PressureThreshold { get; } = new BindableFloat
         {
             MinValue = 0f,
             MaxValue = 1f,
@@ -119,7 +120,34 @@ void IRelativePointer.SetPosition(System.Numerics.Vector2 delta)
             enqueueInput(new MousePositionRelativeInputFromPen { Delta = new Vector2(delta.X, delta.Y), DeviceType = lastTabletDeviceType });
         }
 
-        void IPressureHandler.SetPressure(float percentage) => enqueueInput(new MouseButtonInputFromPen(percentage > PressureThreshold.Value) { DeviceType = lastTabletDeviceType });
+        private bool penPressed;
+
+        void IPressureHandler.SetPressure(float pressure)
+        {
+            // Most important for edge cases where users have pressure set to 0 or 1 and tablets can report fuzzy data.
+            const float hysteresis_half = 0.02f;
+
+            pressure = Math.Clamp(pressure, 0f, 1f);
+
+            float releaseThreshold = PressureThreshold.Value - hysteresis_half;
+            float pressThreshold = PressureThreshold.Value + hysteresis_half;
+
+            // keep press..release threshold range constant for edge cases.
+            if (releaseThreshold < 0f)
+            {
+                pressThreshold = hysteresis_half * 2;
+                releaseThreshold = 0f;
+            }
+            else if (pressThreshold > 1f)
+            {
+                releaseThreshold = 1 - (hysteresis_half * 2);
+                pressThreshold = 1f;
+            }
+
+            setPressed(penPressed
+                ? pressure > releaseThreshold
+                : pressure > pressThreshold);
+        }
 
         private void handleTabletsChanged(object? sender, IEnumerable<TabletReference> tablets)
         {
@@ -135,7 +163,22 @@ private void handleTabletsChanged(object? sender, IEnumerable<TabletReference> t
                 updateOutputArea(host.Window);
             }
             else
+            {
+                // Ensure we don't leave the simulated mouse button pressed if the tablet disappears.
+                setPressed(false);
                 tablet.Value = null;
+            }
+        }
+
+        private void setPressed(bool pressed)
+        {
+            // Importantly, only fire input when the state changes.
+            // If we fire more often, this may intefere with users that click with mouse but use tablet for positional input (hovering).
+            if (pressed == penPressed)
+                return;
+
+            enqueueInput(new MouseButtonInputFromPen(pressed) { DeviceType = lastTabletDeviceType });
+            penPressed = pressed;
         }
 
         private void handleDeviceReported(object? sender, IDeviceReport report)