From 3df9ab4f6354d2bef72e4e97b5e66321f9516043 Mon Sep 17 00:00:00 2001
From: Glen Stone <gstone@thornhillmedical.com>
Date: Mon, 6 Nov 2023 18:45:33 -0500
Subject: [PATCH] DataGrid inertial scroll support (#13502) (#13511)

---
 src/Avalonia.Controls.DataGrid/DataGrid.cs        | 15 +++++++++++++++
 src/Avalonia.Controls.DataGrid/Themes/Fluent.xaml |  8 ++++++--
 src/Avalonia.Controls.DataGrid/Themes/Simple.xaml |  6 ++++--
 3 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/src/Avalonia.Controls.DataGrid/DataGrid.cs b/src/Avalonia.Controls.DataGrid/DataGrid.cs
index 311fb3de40..d7d50f1d6e 100644
--- a/src/Avalonia.Controls.DataGrid/DataGrid.cs
+++ b/src/Avalonia.Controls.DataGrid/DataGrid.cs
@@ -412,6 +412,21 @@ namespace Avalonia.Controls
             }
         }
 
+        /// <summary>
+        /// Defines the <see cref="IsScrollInertiaEnabled"/> property.
+        /// </summary>
+        public static readonly AttachedProperty<bool> IsScrollInertiaEnabledProperty =
+            ScrollViewer.IsScrollInertiaEnabledProperty.AddOwner<DataGrid>();
+
+        /// <summary>
+        /// Gets or sets whether scroll gestures should include inertia in their behavior and value.
+        /// </summary>
+        public bool IsScrollInertiaEnabled
+        {
+            get => GetValue(IsScrollInertiaEnabledProperty);
+            set => SetValue(IsScrollInertiaEnabledProperty, value);
+        }
+
         private bool _isValid = true;
 
         public static readonly DirectProperty<DataGrid, bool> IsValidProperty =
diff --git a/src/Avalonia.Controls.DataGrid/Themes/Fluent.xaml b/src/Avalonia.Controls.DataGrid/Themes/Fluent.xaml
index 2d40721bbf..4f4ae74dd9 100644
--- a/src/Avalonia.Controls.DataGrid/Themes/Fluent.xaml
+++ b/src/Avalonia.Controls.DataGrid/Themes/Fluent.xaml
@@ -532,9 +532,13 @@
               <DataGridRowsPresenter Name="PART_RowsPresenter"
                                      Grid.Row="1"
                                      Grid.RowSpan="2"
-                                     Grid.ColumnSpan="3" Grid.Column="0">
+                                     Grid.ColumnSpan="3"
+                                     Grid.Column="0"
+                                     ScrollViewer.IsScrollInertiaEnabled="{TemplateBinding IsScrollInertiaEnabled}">
                 <DataGridRowsPresenter.GestureRecognizers>
-                  <ScrollGestureRecognizer CanHorizontallyScroll="True" CanVerticallyScroll="True" />
+                  <ScrollGestureRecognizer CanHorizontallyScroll="True"
+                                           CanVerticallyScroll="True"
+                                           IsScrollInertiaEnabled="{Binding (ScrollViewer.IsScrollInertiaEnabled), ElementName=PART_RowsPresenter}" />
                 </DataGridRowsPresenter.GestureRecognizers>
               </DataGridRowsPresenter>
               <Rectangle Name="PART_BottomRightCorner"
diff --git a/src/Avalonia.Controls.DataGrid/Themes/Simple.xaml b/src/Avalonia.Controls.DataGrid/Themes/Simple.xaml
index 66160686b6..71eb1df41f 100644
--- a/src/Avalonia.Controls.DataGrid/Themes/Simple.xaml
+++ b/src/Avalonia.Controls.DataGrid/Themes/Simple.xaml
@@ -335,10 +335,12 @@
 
               <DataGridRowsPresenter Name="PART_RowsPresenter"
                                      Grid.Row="1"
-                                     Grid.ColumnSpan="2">
+                                     Grid.ColumnSpan="2"
+                                     ScrollViewer.IsScrollInertiaEnabled="{TemplateBinding IsScrollInertiaEnabled}">
                 <DataGridRowsPresenter.GestureRecognizers>
                   <ScrollGestureRecognizer CanHorizontallyScroll="True"
-                                           CanVerticallyScroll="True" />
+                                           CanVerticallyScroll="True"
+                                           IsScrollInertiaEnabled="{Binding (ScrollViewer.IsScrollInertiaEnabled), ElementName=PART_RowsPresenter}" />
                 </DataGridRowsPresenter.GestureRecognizers>
               </DataGridRowsPresenter>
               <Rectangle Name="PART_BottomRightCorner"