Enable linking to specific headings in blog

src/Website.Markdig.Extensions/BlogHeadingRenderer.cs

@@ -0,0 +1,25 @@
+using Markdig.Renderers;
+using Markdig.Renderers.Html;
+using Markdig.Syntax;
+using Markdig.Syntax.Inlines;
+using System.Collections.Generic;
+
+namespace Website.Markdig.Extensions
+{
+	public class BlogHeadingRenderer : HtmlObjectRenderer<HeadingBlock> {
+		private readonly HeadingRenderer _baseRenderer;
+
+		public BlogHeadingRenderer(HeadingRenderer baseRenderer) {
+			_baseRenderer = baseRenderer;
+		}
+
+		protected override void Write(HtmlRenderer renderer, HeadingBlock heading) {
+			var htmlAttributes = heading.GetAttributes();
+			if (htmlAttributes.Properties == null)
+				htmlAttributes.Properties = new List<KeyValuePair<string, string>>();
+			var id = (heading.Inline.FirstChild as LiteralInline).Content.ToString().ToLower().Replace(" ", "-");
+			htmlAttributes.Properties.Add(new KeyValuePair<string, string>("id", id));
+			_baseRenderer.Write(renderer, heading);
+		}
+	}
+}

src/Website.Markdig.Extensions/BlogImageRendererExtension.cs

@@ -1,5 +1,6 @@
 using Markdig;
 using Markdig.Renderers;
+using Markdig.Renderers.Html;
 using Markdig.Renderers.Html.Inlines;
 
 namespace Website.Markdig.Extensions {
@@ -8,13 +9,32 @@ namespace Website.Markdig.Extensions {
 
 		}
 
+		private static bool TryRemoveRenderer<T>(HtmlRenderer htmlRenderer, out T originalRenderer) where T : IMarkdownObjectRenderer {
+			originalRenderer = htmlRenderer.ObjectRenderers.FindExact<T>();
+			if (originalRenderer == null)
+				return false;
+			htmlRenderer.ObjectRenderers.Remove(originalRenderer);
+			return true;
+		}
+
+		private static void ReplaceImageRenderer(HtmlRenderer htmlRenderer) {
+			if (TryRemoveRenderer<LinkInlineRenderer>(htmlRenderer, out var originalRenderer)) {
+				var blogRenderer = new BlogLinkAndImageRenderer(originalRenderer);
+				htmlRenderer.ObjectRenderers.AddIfNotAlready(blogRenderer);
+			}
+		}
+
+		private void ReplaceHeadingRenderer(HtmlRenderer htmlRenderer) {
+			if (TryRemoveRenderer<HeadingRenderer>(htmlRenderer, out var originalRenderer)) {
+				var blogRenderer = new BlogHeadingRenderer(originalRenderer);
+				htmlRenderer.ObjectRenderers.AddIfNotAlready(blogRenderer);
+			}
+		}
+
 		public void Setup(MarkdownPipeline pipeline, IMarkdownRenderer renderer) {
 			var htmlRenderer = renderer as HtmlRenderer;
-			var originalRenderer = htmlRenderer.ObjectRenderers.FindExact<LinkInlineRenderer>();
+			ReplaceImageRenderer(htmlRenderer);
-			if (originalRenderer != null)
+			ReplaceHeadingRenderer(htmlRenderer);
-				htmlRenderer.ObjectRenderers.Remove(originalRenderer);
-			var blogRenderer = new BlogLinkAndImageRenderer(originalRenderer);
-			htmlRenderer.ObjectRenderers.AddIfNotAlready(blogRenderer);
 		}
 	}
 }

src/Website.Markdig.Extensions/Website.Markdig.Extensions.csproj

@@ -4,8 +4,8 @@
     <TargetFramework>netstandard2.0</TargetFramework>
   </PropertyGroup>
 
-  <ItemGroup>
+  <ItemGroup>
-    <PackageReference Include="markdig" Version="0.18.3" />
+    <PackageReference Include="markdig" Version="0.24.0" />
   </ItemGroup>
 
 </Project>

src/Website/Website.csproj

@@ -8,7 +8,7 @@
 
   <ItemGroup>
     <PackageReference Include="BuildBundlerMinifier" Version="3.2.435" />
-    <PackageReference Include="markdig" Version="0.18.3" />
+    <PackageReference Include="markdig" Version="0.24.0" />
     <PackageReference Include="Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation" Version="3.1.0" />
     <PackageReference Include="Newtonsoft.Json" Version="12.0.3" />
     <PackageReference Include="Pek.Markdig.HighlightJs" Version="0.5.1" />