MarkdownTextBlock Code Block Scrolling Fix

Microsoft.Toolkit.Uwp.UI.Controls/MarkdownTextBlock/Render/MarkdownRenderer.Blocks.cs

@@ -328,6 +328,8 @@ protected override void RenderCode(CodeBlock element, IRenderContext context)
                 LineHeight = FontSize * 1.4
             };
 
+            textBlock.PointerWheelChanged += Preventative_PointerWheelChanged;
+
             var paragraph = new Paragraph();
             textBlock.Blocks.Add(paragraph);
 

Microsoft.Toolkit.Uwp.UI.Controls/MarkdownTextBlock/Render/MarkdownRenderer.Inlines.cs

@@ -250,23 +250,33 @@ protected override async void RenderImage(ImageInline element, IRenderContext co
                 return;
             }
 
-            var image = new Image();
-            var scrollViewer = new ScrollViewer();
-            var viewbox = new Viewbox();
-            scrollViewer.Content = viewbox;
-            viewbox.Child = image;
+            var image = new Image
+            {
+                Source = resolvedImage,
+                HorizontalAlignment = HorizontalAlignment.Left,
+                VerticalAlignment = VerticalAlignment.Top,
+                Stretch = ImageStretch
+            };
+
+            var viewbox = new Viewbox
+            {
+                Child = image,
+                StretchDirection = StretchDirection.DownOnly
+            };
+
+            viewbox.PointerWheelChanged += Preventative_PointerWheelChanged;
+
+            var scrollViewer = new ScrollViewer
+            {
+                Content = viewbox,
+                VerticalScrollMode = ScrollMode.Disabled,
+                VerticalScrollBarVisibility = ScrollBarVisibility.Disabled
+            };
+
             var imageContainer = new InlineUIContainer() { Child = scrollViewer };
 
             LinkRegister.RegisterNewHyperLink(image, element.Url);
 
-            image.Source = resolvedImage;
-            image.HorizontalAlignment = HorizontalAlignment.Left;
-            image.VerticalAlignment = VerticalAlignment.Top;
-            image.Stretch = ImageStretch;
-            scrollViewer.VerticalScrollMode = ScrollMode.Disabled;
-            scrollViewer.VerticalScrollBarVisibility = ScrollBarVisibility.Disabled;
-            viewbox.StretchDirection = StretchDirection.DownOnly;
-
             if (ImageMaxHeight > 0)
             {
                 viewbox.MaxHeight = ImageMaxHeight;

Microsoft.Toolkit.Uwp.UI.Controls/MarkdownTextBlock/Render/MarkdownRenderer.Properties.cs

@@ -10,8 +10,11 @@
 // THE CODE OR THE USE OR OTHER DEALINGS IN THE CODE.
 // ******************************************************************
 
+using System.Reflection;
 using Windows.Foundation.Metadata;
 using Windows.UI.Text;
+using Windows.UI.Xaml;
+using Windows.UI.Xaml.Controls;
 using Windows.UI.Xaml.Media;
 
 namespace Microsoft.Toolkit.Uwp.UI.Controls.Markdown.Render
@@ -26,6 +29,16 @@ public partial class MarkdownRenderer
         private static bool TextDecorationsSupported => (bool)(_textDecorationsSupported ??
                         (_textDecorationsSupported = ApiInformation.IsTypePresent("Windows.UI.Text.TextDecorations")));
 
+        /// <summary>
+        /// Super Hack to retain inertia and passing the Scroll data onto the Parent ScrollViewer.
+        /// </summary>
+        private static MethodInfo pointerWheelChanged = typeof(ScrollViewer).GetMethod("OnPointerWheelChanged", BindingFlags.NonPublic | BindingFlags.Instance);
+
+        /// <summary>
+        /// Gets or sets the Root Framework Element.
+        /// </summary>
+        private FrameworkElement RootElement { get; set; }
+
         /// <summary>
         /// Gets the interface that is used to register hyperlinks.
         /// </summary>

Microsoft.Toolkit.Uwp.UI.Controls/MarkdownTextBlock/Render/MarkdownRenderer.cs

@@ -15,6 +15,7 @@
 using Microsoft.Toolkit.Parsers.Markdown;
 using Microsoft.Toolkit.Parsers.Markdown.Inlines;
 using Microsoft.Toolkit.Parsers.Markdown.Render;
+using Microsoft.Toolkit.Uwp.UI.Extensions;
 using Windows.UI.Xaml;
 using Windows.UI.Xaml.Controls;
 using Windows.UI.Xaml.Documents;
@@ -50,6 +51,7 @@ public MarkdownRenderer(MarkdownDocument document, ILinkRegister linkRegister, I
         public UIElement Render()
         {
             var stackPanel = new StackPanel();
+            RootElement = stackPanel;
             Render(new UIElementCollectionRenderContext(stackPanel.Children) { Foreground = Foreground });
 
             // Set background and border properties.
@@ -207,5 +209,23 @@ private void RemoveSuperscriptRuns(IInlineContainer container, bool insertCaret)
                 }
             }
         }
+
+        private void Preventative_PointerWheelChanged(object sender, Windows.UI.Xaml.Input.PointerRoutedEventArgs e)
+        {
+            var pointerPoint = e.GetCurrentPoint((UIElement)sender);
+
+            if (pointerPoint.Properties.IsHorizontalMouseWheel)
+            {
+                e.Handled = false;
+                return;
+            }
+
+            var rootViewer = VisualTree.FindAscendant<ScrollViewer>(RootElement);
+            if (rootViewer != null)
+            {
+                pointerWheelChanged?.Invoke(rootViewer, new object[] { e });
+                e.Handled = true;
+            }
+        }
     }
 }