From e3c6ee0da3ee703e32c956d1521a37a7e0c86165 Mon Sep 17 00:00:00 2001
From: Tom Edwards <t.edwards@enscape3d.com>
Date: Fri, 31 Mar 2023 21:08:06 +0200
Subject: [PATCH] Convert ScrollGestureRecognizer to an unstyled element Added
 missing binding of IsScrollInertiaEnabled in the simple theme

---
 .../ScrollGestureRecognizer.cs                | 53 +++++++++++--------
 .../Controls/ScrollViewer.xaml                |  2 +-
 .../Controls/ScrollViewer.xaml                |  3 +-
 3 files changed, 33 insertions(+), 25 deletions(-)

diff --git a/src/Avalonia.Base/Input/GestureRecognizers/ScrollGestureRecognizer.cs b/src/Avalonia.Base/Input/GestureRecognizers/ScrollGestureRecognizer.cs
index 1ad2f292ca..b510d44e63 100644
--- a/src/Avalonia.Base/Input/GestureRecognizers/ScrollGestureRecognizer.cs
+++ b/src/Avalonia.Base/Input/GestureRecognizers/ScrollGestureRecognizer.cs
@@ -4,14 +4,17 @@ using Avalonia.Threading;
 
 namespace Avalonia.Input.GestureRecognizers
 {
-    public class ScrollGestureRecognizer 
-        : StyledElement, // It's not an "element" in any way, shape or form, but TemplateBinding refuse to work otherwise
-            IGestureRecognizer
+    public class ScrollGestureRecognizer : AvaloniaObject, IGestureRecognizer
     {
         // Pixels per second speed that is considered to be the stop of inertial scroll
         internal const double InertialScrollSpeedEnd = 5;
         public const double InertialResistance = 0.15;
 
+        private bool _canHorizontallyScroll;
+        private bool _canVerticallyScroll;
+        private bool _isScrollInertiaEnabled;
+        private int _scrollStartDistance = 30;
+
         private bool _scrolling;
         private Point _trackedRootPoint;
         private IPointer? _tracking;
@@ -28,34 +31,39 @@ namespace Avalonia.Input.GestureRecognizers
         /// <summary>
         /// Defines the <see cref="CanHorizontallyScroll"/> property.
         /// </summary>
-        public static readonly StyledProperty<bool> CanHorizontallyScrollProperty =
-            AvaloniaProperty.Register<ScrollGestureRecognizer, bool>(nameof(CanHorizontallyScroll));
+        public static readonly DirectProperty<ScrollGestureRecognizer, bool> CanHorizontallyScrollProperty =
+            AvaloniaProperty.RegisterDirect<ScrollGestureRecognizer, bool>(nameof(CanHorizontallyScroll), 
+                o => o.CanHorizontallyScroll, (o, v) => o.CanHorizontallyScroll = v);
 
         /// <summary>
         /// Defines the <see cref="CanVerticallyScroll"/> property.
         /// </summary>
-        public static readonly StyledProperty<bool> CanVerticallyScrollProperty =
-            AvaloniaProperty.Register<ScrollGestureRecognizer, bool>(nameof(CanVerticallyScroll));
+        public static readonly DirectProperty<ScrollGestureRecognizer, bool> CanVerticallyScrollProperty =
+            AvaloniaProperty.RegisterDirect<ScrollGestureRecognizer, bool>(nameof(CanVerticallyScroll),
+                o => o.CanVerticallyScroll, (o, v) => o.CanVerticallyScroll = v);
 
         /// <summary>
         /// Defines the <see cref="IsScrollInertiaEnabled"/> property.
         /// </summary>
-        public static readonly StyledProperty<bool> IsScrollInertiaEnabledProperty =
-            AvaloniaProperty.Register<ScrollGestureRecognizer, bool>(nameof(IsScrollInertiaEnabled));
+        public static readonly DirectProperty<ScrollGestureRecognizer, bool> IsScrollInertiaEnabledProperty =
+            AvaloniaProperty.RegisterDirect<ScrollGestureRecognizer, bool>(nameof(IsScrollInertiaEnabled),
+                o => o.IsScrollInertiaEnabled, (o,v) => o.IsScrollInertiaEnabled = v);
 
         /// <summary>
         /// Defines the <see cref="ScrollStartDistance"/> property.
         /// </summary>
-        public static readonly StyledProperty<int> ScrollStartDistanceProperty =
-            AvaloniaProperty.Register<ScrollGestureRecognizer, int>(nameof(ScrollStartDistance), 30);
-        
+        public static readonly DirectProperty<ScrollGestureRecognizer, int> ScrollStartDistanceProperty =
+            AvaloniaProperty.RegisterDirect<ScrollGestureRecognizer, int>(nameof(ScrollStartDistance),
+                o => o.ScrollStartDistance, (o, v) => o.ScrollStartDistance = v,
+                unsetValue: 30);
+
         /// <summary>
         /// Gets or sets a value indicating whether the content can be scrolled horizontally.
         /// </summary>
         public bool CanHorizontallyScroll
         {
-            get => GetValue(CanHorizontallyScrollProperty);
-            set => SetValue(CanHorizontallyScrollProperty, value);
+            get => _canHorizontallyScroll;
+            set => SetAndRaise(CanHorizontallyScrollProperty, ref _canHorizontallyScroll, value);
         }
 
         /// <summary>
@@ -63,17 +71,17 @@ namespace Avalonia.Input.GestureRecognizers
         /// </summary>
         public bool CanVerticallyScroll
         {
-            get => GetValue(CanVerticallyScrollProperty);
-            set => SetValue(CanVerticallyScrollProperty, value);
+            get => _canVerticallyScroll;
+            set => SetAndRaise(CanVerticallyScrollProperty, ref _canVerticallyScroll, value);
         }
-        
+
         /// <summary>
         /// Gets or sets whether the gesture should include inertia in it's behavior.
         /// </summary>
         public bool IsScrollInertiaEnabled
         {
-            get => GetValue(IsScrollInertiaEnabledProperty);
-            set => SetValue(IsScrollInertiaEnabledProperty, value);
+            get => _isScrollInertiaEnabled;
+            set => SetAndRaise(IsScrollInertiaEnabledProperty, ref _isScrollInertiaEnabled, value);
         }
 
         /// <summary>
@@ -81,10 +89,9 @@ namespace Avalonia.Input.GestureRecognizers
         /// </summary>
         public int ScrollStartDistance
         {
-            get => GetValue(ScrollStartDistanceProperty);
-            set => SetValue(ScrollStartDistanceProperty, value);
-        }
-        
+            get => _scrollStartDistance;
+            set => SetAndRaise(ScrollStartDistanceProperty, ref _scrollStartDistance, value);
+        }        
 
         public void Initialize(IInputElement target, IGestureRecognizerActionsDispatcher actions)
         {
diff --git a/src/Avalonia.Themes.Fluent/Controls/ScrollViewer.xaml b/src/Avalonia.Themes.Fluent/Controls/ScrollViewer.xaml
index 04b8f80f82..1d9815713c 100644
--- a/src/Avalonia.Themes.Fluent/Controls/ScrollViewer.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/ScrollViewer.xaml
@@ -37,7 +37,7 @@
             <ScrollContentPresenter.GestureRecognizers>
               <ScrollGestureRecognizer CanHorizontallyScroll="{Binding CanHorizontallyScroll, ElementName=PART_ContentPresenter}"
                                        CanVerticallyScroll="{Binding CanVerticallyScroll, ElementName=PART_ContentPresenter}"
-                                       IsScrollInertiaEnabled="{TemplateBinding IsScrollInertiaEnabled}" />
+                                       IsScrollInertiaEnabled="{Binding IsScrollInertiaEnabled, RelativeSource={RelativeSource TemplatedParent}}" />
             </ScrollContentPresenter.GestureRecognizers>
           </ScrollContentPresenter>
           <ScrollBar Name="PART_HorizontalScrollBar"
diff --git a/src/Avalonia.Themes.Simple/Controls/ScrollViewer.xaml b/src/Avalonia.Themes.Simple/Controls/ScrollViewer.xaml
index c0f17c2a9a..724adbddd8 100644
--- a/src/Avalonia.Themes.Simple/Controls/ScrollViewer.xaml
+++ b/src/Avalonia.Themes.Simple/Controls/ScrollViewer.xaml
@@ -17,7 +17,8 @@
                                   Background="{TemplateBinding Background}">
             <ScrollContentPresenter.GestureRecognizers>
               <ScrollGestureRecognizer CanHorizontallyScroll="{Binding CanHorizontallyScroll, ElementName=PART_ContentPresenter}"
-                                       CanVerticallyScroll="{Binding CanVerticallyScroll, ElementName=PART_ContentPresenter}" />
+                                       CanVerticallyScroll="{Binding CanVerticallyScroll, ElementName=PART_ContentPresenter}"
+                                       IsScrollInertiaEnabled="{Binding IsScrollInertiaEnabled, RelativeSource={RelativeSource TemplatedParent}}" />
             </ScrollContentPresenter.GestureRecognizers>
           </ScrollContentPresenter>
           <ScrollBar Name="PART_HorizontalScrollBar"