add comments

src/Avalonia.Controls/Presenters/ScrollContentPresenter.cs

@@ -178,24 +178,36 @@ namespace Avalonia.Controls.Presenters
             private set { SetAndRaise(ViewportProperty, ref _viewport, value); }
         }
 
+        /// <summary>
+        /// Gets or sets how scroll gesture reacts to the snap points along the horizontal axis.
+        /// </summary>
         public SnapPointsType HorizontalSnapPointsType
         {
-            get => GetValue(HorizontalSnapPointsTypeProperty); 
+            get => GetValue(HorizontalSnapPointsTypeProperty);
             set => SetValue(HorizontalSnapPointsTypeProperty, value);
         }
 
+        /// <summary>
+        /// Gets or sets how scroll gesture reacts to the snap points along the vertical axis.
+        /// </summary>
         public SnapPointsType VerticalSnapPointsType
         {
-            get => GetValue(VerticalSnapPointsTypeProperty); 
+            get => GetValue(VerticalSnapPointsTypeProperty);
             set => SetValue(VerticalSnapPointsTypeProperty, value);
         }
 
+        /// <summary>
+        /// Gets or sets how the existing snap points are horizontally aligned versus the initial viewport.
+        /// </summary>
         public SnapPointsAlignment HorizontalSnapPointsAlignment
         {
-            get => GetValue(HorizontalSnapPointsAlignmentProperty); 
+            get => GetValue(HorizontalSnapPointsAlignmentProperty);
             set => SetValue(HorizontalSnapPointsAlignmentProperty, value);
         }
 
+        /// <summary>
+        /// Gets or sets how the existing snap points are vertically aligned versus the initial viewport.
+        /// </summary>
         public SnapPointsAlignment VerticalSnapPointsAlignment
         {
             get => GetValue(VerticalSnapPointsAlignmentProperty); 

src/Avalonia.Controls/ScrollViewer.cs

@@ -449,24 +449,36 @@ namespace Avalonia.Controls
             private set => SetAndRaise(ScrollBar.IsExpandedProperty, ref _isExpanded, value);
         }
 
+        /// <summary>
+        /// Gets or sets how scroll gesture reacts to the snap points along the horizontal axis.
+        /// </summary>
         public SnapPointsType HorizontalSnapPointsType
         {
             get => GetValue(HorizontalSnapPointsTypeProperty);
             set => SetValue(HorizontalSnapPointsTypeProperty, value);
         }
 
+        /// <summary>
+        /// Gets or sets how scroll gesture reacts to the snap points along the vertical axis.
+        /// </summary>
         public SnapPointsType VerticalSnapPointsType
         {
             get => GetValue(VerticalSnapPointsTypeProperty);
             set => SetValue(VerticalSnapPointsTypeProperty, value);
         }
 
+        /// <summary>
+        /// Gets or sets how the existing snap points are horizontally aligned versus the initial viewport.
+        /// </summary>
         public SnapPointsAlignment HorizontalSnapPointsAlignment
         {
             get => GetValue(HorizontalSnapPointsAlignmentProperty); 
             set => SetValue(HorizontalSnapPointsAlignmentProperty, value);
         }
 
+        /// <summary>
+        /// Gets or sets how the existing snap points are vertically aligned versus the initial viewport.
+        /// </summary>
         public SnapPointsAlignment VerticalSnapPointsAlignment
         {
             get => GetValue(VerticalSnapPointsAlignmentProperty); 

src/Avalonia.Controls/StackPanel.cs

@@ -85,25 +85,36 @@ namespace Avalonia.Controls
             set { SetValue(OrientationProperty, value); }
         }
 
+        /// <summary>
+        /// Occurs when the measurements for horizontal snap points change.
+        /// </summary>
         public event EventHandler<RoutedEventArgs>? HorizontalSnapPointsChanged
         {
             add => AddHandler(HorizontalSnapPointsChangedEvent, value);
             remove => RemoveHandler(HorizontalSnapPointsChangedEvent, value);
         }
 
-
+        /// <summary>
+        /// Occurs when the measurements for vertical snap points change.
+        /// </summary>
         public event EventHandler<RoutedEventArgs>? VerticalSnapPointsChanged
         {
             add => AddHandler(VerticalSnapPointsChangedEvent, value);
             remove => RemoveHandler(VerticalSnapPointsChangedEvent, value);
         }
 
+        /// <summary>
+        /// Gets or sets whether the horizontal snap points for the <see cref="StackPanel"/> are equidistant from each other.
+        /// </summary>
         public bool AreHorizontalSnapPointsRegular
         {
             get { return GetValue(AreHorizontalSnapPointsRegularProperty); }
             set { SetValue(AreHorizontalSnapPointsRegularProperty, value); }
         }
 
+        /// <summary>
+        /// Gets or sets whether the vertical snap points for the <see cref="StackPanel"/> are equidistant from each other.
+        /// </summary>
         public bool AreVerticalSnapPointsRegular
         {
             get { return GetValue(AreVerticalSnapPointsRegularProperty); }