Add support for in-document linking (e.g. #my-id).

Documents/Markdig-readme.md

@@ -1,4 +1,11 @@
-# Markdig [![Build status](https://ci.appveyor.com/api/projects/status/hk391x8jcskxt1u8?svg=true)](https://ci.appveyor.com/project/xoofx/markdig) [![NuGet](https://img.shields.io/nuget/v/Markdig.svg)](https://www.nuget.org/packages/Markdig/) [![Donate](https://www.paypalobjects.com/en_US/i/btn/btn_donate_SM.gif)](https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=FRGHXBTP442JL)
+* [Markdig](#markdig)
+  * [Features](#features)
+  * [Documentation](#documentation)
+  * [Download](#download)
+  * [Usage](#usage)
+
+
+# Markdig [![Build status](https://ci.appveyor.com/api/projects/status/hk391x8jcskxt1u8?svg=true)](https://ci.appveyor.com/project/xoofx/markdig) [![NuGet](https://img.shields.io/nuget/v/Markdig.svg)](https://www.nuget.org/packages/Markdig/) [![Donate](https://www.paypalobjects.com/en_US/i/btn/btn_donate_SM.gif)](https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=FRGHXBTP442JL)
 
 | Tables        | Are           | Cool  |
 | ------------- |:-------------:| -----:|

src/Markdig.Wpf/Commands.cs

@@ -20,5 +20,10 @@ public static class Commands
         /// Routed command for Images.
         /// </summary>
         public static RoutedCommand Image { get; } = new RoutedCommand(nameof(Image), typeof(Commands));
+
+        /// <summary>
+        /// Routed command for navigating to a heading in a document. Command parameter contains the heading id
+        /// </summary>
+        public static RoutedCommand Navigate { get; } = new RoutedCommand(nameof(Navigate), typeof(Commands));
     }
 }

src/Markdig.Wpf/MarkdownExtensions.cs

@@ -25,7 +25,8 @@ public static MarkdownPipelineBuilder UseSupportedExtensions(this MarkdownPipeli
                 .UseGridTables()
                 .UsePipeTables()
                 .UseTaskLists()
-                .UseAutoLinks();
+                .UseAutoLinks()
+                .UseAutoIdentifiers();
         }
     }
 }

src/Markdig.Wpf/MarkdownViewer.cs

@@ -2,9 +2,12 @@
 // This file is licensed under the MIT license.
 // See the LICENSE.md file in the project root for more information.
 
+using System;
 using System.Windows;
 using System.Windows.Controls;
 using System.Windows.Documents;
+using System.Windows.Input;
+using System.Windows.Media;
 
 namespace Markdig.Wpf
 {
@@ -35,11 +38,28 @@ public class MarkdownViewer : Control
         public static readonly DependencyProperty PipelineProperty =
             DependencyProperty.Register(nameof(Pipeline), typeof(MarkdownPipeline), typeof(MarkdownViewer), new FrameworkPropertyMetadata(PipelineChanged));
 
+        /// <summary>
+        /// Defines the MarkdownViewer.AnchorName attached property used for in-document linking (e.g. "#my-id")
+        /// </summary>
+        public static readonly DependencyProperty AnchorNameProperty = DependencyProperty.RegisterAttached(
+            "AnchorName", typeof(string), typeof(MarkdownViewer), new PropertyMetadata(default(string)));
+
+        public static void SetAnchorName(DependencyObject element, string value)
+        {
+            element.SetValue(AnchorNameProperty, value);
+        }
+
+        public static string GetAnchorName(DependencyObject element)
+        {
+            return (string)element.GetValue(AnchorNameProperty);
+        }
         static MarkdownViewer()
         {
             DefaultStyleKeyProperty.OverrideMetadata(typeof(MarkdownViewer), new FrameworkPropertyMetadata(typeof(MarkdownViewer)));
         }
 
+        private FlowDocumentScrollViewer? docViewer;
+
         /// <summary>
         /// Gets the flow document to display.
         /// </summary>
@@ -79,9 +99,88 @@ private static void PipelineChanged(object sender, DependencyPropertyChangedEven
             control.RefreshDocument();
         }
 
+        public MarkdownViewer()
+        {
+            CommandBindings.Add(new CommandBinding(Commands.Navigate, NavigateCommandExecuted));
+        }
+
+        private void NavigateCommandExecuted(object sender, ExecutedRoutedEventArgs e)
+        {
+            string url = e.Parameter?.ToString() ?? "";
+            if (url.Length > 1 && url[0] == '#')
+            {
+                string anchorName = url.Substring(1);
+                e.Handled = NavigateTo(anchorName);
+            }
+        }
+
         protected virtual void RefreshDocument()
         {
             Document = Markdown != null ? Wpf.Markdown.ToFlowDocument(Markdown, Pipeline ?? DefaultPipeline) : null;
         }
+
+        public override void OnApplyTemplate()
+        {
+            docViewer =  GetTemplateChild("PART_DocViewer") as FlowDocumentScrollViewer;
+
+            base.OnApplyTemplate();
+        }
+
+        public bool NavigateTo(string anchorName)
+        {
+            if (Document == null)
+                throw new InvalidOperationException("No rendered content found");
+
+            foreach (var block in Document.Blocks)
+            {
+                string blockAnchorName = GetAnchorName(block);
+                if (String.Equals(blockAnchorName, anchorName, StringComparison.OrdinalIgnoreCase))
+                {
+                    return ScrollIntoView(block);
+                }
+            }
+
+            return false;
+        }
+
+        private bool ScrollIntoView(Block block)
+        {
+            if (docViewer == null)
+                return false;
+            double top = block.ContentStart.GetCharacterRect(LogicalDirection.Forward).Top;
+            var scrollViewer = FindVisualChild<ScrollViewer>(docViewer);
+            if (scrollViewer != null)
+            {
+                scrollViewer.ScrollToVerticalOffset(top);
+                return true;
+            }
+
+            return false;
+        }
+
+        /// <summary>
+        /// Gets a visual child of the specific type.
+        /// </summary>
+        /// <typeparam name="T">The type of child to find.</typeparam>
+        /// <param name="element">Where to start the "search".</param>
+        /// <returns>The child or null.</returns>
+        public static T? FindVisualChild<T>(
+            DependencyObject element) where T : class
+        {
+            if (element is T retVal)
+                return retVal;
+
+            int childCnt = VisualTreeHelper.GetChildrenCount(element);
+            for (int i = 0; i < childCnt; ++i)
+            {
+                DependencyObject child = VisualTreeHelper.GetChild(element, i);
+
+                var result = FindVisualChild<T>(child);
+                if (result != null)
+                    return result;
+            }
+
+            return null;
+        }
     }
 }

src/Markdig.Wpf/Renderers/Wpf/HeadingRenderer.cs

@@ -5,7 +5,7 @@
 using System;
 using System.Windows;
 using System.Windows.Documents;
-
+using Markdig.Renderers.Html;
 using Markdig.Syntax;
 using Markdig.Wpf;
 
@@ -36,6 +36,12 @@ protected override void Write(WpfRenderer renderer, HeadingBlock obj)
                 paragraph.SetResourceReference(FrameworkContentElement.StyleProperty, styleKey);
             }
 
+            var attributes = obj.TryGetAttributes();
+            if (!String.IsNullOrEmpty(attributes?.Id))
+            {
+                MarkdownViewer.SetAnchorName(paragraph, attributes.Id);
+            }
+
             renderer.Push(paragraph);
             renderer.WriteLeafInline(obj);
             renderer.Pop();

src/Markdig.Wpf/Renderers/Wpf/Inlines/LinkInlineRenderer.cs

@@ -27,7 +27,7 @@ protected override void Write(WpfRenderer renderer, LinkInline link)
 
             var url = link.GetDynamicUrl != null ? link.GetDynamicUrl() ?? link.Url : link.Url;
 
-            if (!Uri.IsWellFormedUriString(url, UriKind.RelativeOrAbsolute))
+            if (!Uri.TryCreate(url, UriKind.RelativeOrAbsolute, out _))
             {
                 url = "#";
             }
@@ -53,12 +53,11 @@ protected override void Write(WpfRenderer renderer, LinkInline link)
             {
                 var hyperlink = new Hyperlink
                 {
-                    Command = Commands.Hyperlink,
+                    Command = url.StartsWith("#") ? Commands.Navigate : Commands.Hyperlink,
                     CommandParameter = url,
                     NavigateUri = new Uri(url, UriKind.RelativeOrAbsolute),
                     ToolTip = !string.IsNullOrEmpty(link.Title) ? link.Title : null,
                 };
-
                 hyperlink.SetResourceReference(FrameworkContentElement.StyleProperty, Styles.HyperlinkStyleKey);
 
                 renderer.Push(hyperlink);

src/Markdig.Wpf/Themes/generic.xaml

@@ -99,6 +99,7 @@
       <Setter.Value>
         <ControlTemplate TargetType="markdig:MarkdownViewer">
           <FlowDocumentScrollViewer Document="{TemplateBinding Document}"
+                                    x:Name="PART_DocViewer"
                                     ScrollViewer.VerticalScrollBarVisibility="Auto"/>
         </ControlTemplate>
       </Setter.Value>