From 5c74e2c32bc401cc26b8d80f61e7e57ea4804c34 Mon Sep 17 00:00:00 2001
From: robloo <robloo@users.noreply.github.com>
Date: Sat, 13 May 2023 14:26:35 -0400
Subject: [PATCH] Add RangeBase.ValueChanged event

---
 .../RoutedPropertyChangedEventArgs.cs         | 46 +++++++++++++++++++
 src/Avalonia.Controls/Primitives/RangeBase.cs | 37 ++++++++++++++-
 2 files changed, 81 insertions(+), 2 deletions(-)
 create mode 100644 src/Avalonia.Base/Interactivity/RoutedPropertyChangedEventArgs.cs

diff --git a/src/Avalonia.Base/Interactivity/RoutedPropertyChangedEventArgs.cs b/src/Avalonia.Base/Interactivity/RoutedPropertyChangedEventArgs.cs
new file mode 100644
index 0000000000..22134b518d
--- /dev/null
+++ b/src/Avalonia.Base/Interactivity/RoutedPropertyChangedEventArgs.cs
@@ -0,0 +1,46 @@
+namespace Avalonia.Interactivity
+{
+    /// <summary>
+    /// Provides both old and new property values with a routed event.
+    /// </summary>
+    /// <typeparam name="T">The type of values.</typeparam>
+    public class RoutedPropertyChangedEventArgs<T> : RoutedEventArgs
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="RoutedPropertyChangedEventArgs{T}"/> class.
+        /// </summary>
+        /// <param name="oldValue">The old property value.</param>
+        /// <param name="newValue">The new property value.</param>
+        /// <param name="routedEvent">The routed event associated with these event args.</param>
+        public RoutedPropertyChangedEventArgs(T oldValue, T newValue, RoutedEvent? routedEvent)
+            : base(routedEvent)
+        {
+            OldValue = oldValue;
+            NewValue = newValue;
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="RoutedPropertyChangedEventArgs{T}"/> class.
+        /// </summary>
+        /// <param name="oldValue">The old property value.</param>
+        /// <param name="newValue">The new property value.</param>
+        /// <param name="routedEvent">The routed event associated with these event args.</param>
+        /// <param name="source">The source object that raised the routed event.</param>
+        public RoutedPropertyChangedEventArgs(T oldValue, T newValue, RoutedEvent? routedEvent, object? source)
+            : base(routedEvent, source)
+        {
+            OldValue = oldValue;
+            NewValue = newValue;
+        }
+
+        /// <summary>
+        /// Gets the old value of the property.
+        /// </summary>
+        public T OldValue { get; init; }
+
+        /// <summary>
+        /// Gets the new value of the property.
+        /// </summary>
+        public T NewValue { get; init; }
+    }
+}
diff --git a/src/Avalonia.Controls/Primitives/RangeBase.cs b/src/Avalonia.Controls/Primitives/RangeBase.cs
index fd9de47236..ebf7879412 100644
--- a/src/Avalonia.Controls/Primitives/RangeBase.cs
+++ b/src/Avalonia.Controls/Primitives/RangeBase.cs
@@ -1,5 +1,6 @@
 using System;
 using Avalonia.Data;
+using Avalonia.Interactivity;
 using Avalonia.Utilities;
 
 namespace Avalonia.Controls.Primitives
@@ -42,7 +43,23 @@ namespace Avalonia.Controls.Primitives
             AvaloniaProperty.Register<RangeBase, double>(nameof(LargeChange), 10);
 
         /// <summary>
-        /// Gets or sets the minimum value.
+        /// Defines the <see cref="ValueChanged"/> event.
+        /// </summary>
+        public static readonly RoutedEvent<RoutedPropertyChangedEventArgs<double>> ValueChangedEvent =
+            RoutedEvent.Register<RangeBase, RoutedPropertyChangedEventArgs<double>>(
+                nameof(ValueChanged), RoutingStrategies.Bubble);
+
+        /// <summary>
+        /// Occurs when the <see cref="Value"/> property changes.
+        /// </summary>
+        public event EventHandler<RoutedPropertyChangedEventArgs<double>>? ValueChanged
+        {
+            add => AddHandler(ValueChangedEvent, value);
+            remove => RemoveHandler(ValueChangedEvent, value);
+        }
+
+        /// <summary>
+        /// Gets or sets the minimum possible value.
         /// </summary>
         public double Minimum
         {
@@ -65,7 +82,7 @@ namespace Avalonia.Controls.Primitives
         }
 
         /// <summary>
-        /// Gets or sets the maximum value.
+        /// Gets or sets the maximum possible value.
         /// </summary>
         public double Maximum
         {
@@ -104,18 +121,25 @@ namespace Avalonia.Controls.Primitives
                 : sender.GetValue(ValueProperty);
         }
 
+        /// <summary>
+        /// Gets or sets the small increment value added or subtracted from the <see cref="Value"/>.
+        /// </summary>
         public double SmallChange
         {
             get => GetValue(SmallChangeProperty);
             set => SetValue(SmallChangeProperty, value);
         }
 
+        /// <summary>
+        /// Gets or sets the large increment value added or subtracted from the <see cref="Value"/>.
+        /// </summary>
         public double LargeChange
         {
             get => GetValue(LargeChangeProperty);
             set => SetValue(LargeChangeProperty, value);
         }
 
+        /// <inheritdoc/>
         protected override void OnInitialized()
         {
             base.OnInitialized();
@@ -124,6 +148,7 @@ namespace Avalonia.Controls.Primitives
             CoerceValue(ValueProperty);
         }
 
+        /// <inheritdoc/>
         protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change)
         {
             base.OnPropertyChanged(change);
@@ -136,6 +161,14 @@ namespace Avalonia.Controls.Primitives
             {
                 OnMaximumChanged();
             }
+            else if (change.Property == ValueProperty)
+            {
+                var valueChangedEventArgs = new RoutedPropertyChangedEventArgs<double>(
+                    change.GetOldValue<double>(),
+                    change.GetNewValue<double>(),
+                    ValueChangedEvent);
+                RaiseEvent(valueChangedEventArgs);
+            }
         }
 
         /// <summary>