MarkdownTextBlock: Rewrite lists to be text-based

Author: Juan Osorio

components/MarkdownTextBlock/src/MarkdownTextBlock.xaml.cs

@@ -106,7 +106,8 @@ private void Build()
 
                 // Default block renderers
                 _renderer.ObjectRenderers.Add(new CodeBlockRenderer());
-                _renderer.ObjectRenderers.Add(new ListRenderer());
+                _renderer.ObjectRenderers.Add(new ListRenderer());
+                _renderer.ObjectRenderers.Add(new ListItemRenderer());
                 _renderer.ObjectRenderers.Add(new HeadingRenderer());
                 _renderer.ObjectRenderers.Add(new ParagraphRenderer());
                 _renderer.ObjectRenderers.Add(new QuoteBlockRenderer());

components/MarkdownTextBlock/src/Renderers/ObjectRenderers/ListItemRenderer.cs

@@ -0,0 +1,18 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Markdig.Syntax;
+
+namespace CommunityToolkit.Labs.WinUI.MarkdownTextBlock.Renderers.ObjectRenderers;
+
+internal class ListItemRenderer : UWPObjectRenderer<ListItemBlock>
+{
+    protected override void Write(WinUIRenderer renderer, ListItemBlock listItem)
+    {
+        if (renderer == null) throw new ArgumentNullException(nameof(renderer));
+        if (listItem == null) throw new ArgumentNullException(nameof(listItem));
+
+        renderer.WriteChildren(listItem);
+    }
+}

components/MarkdownTextBlock/src/Renderers/ObjectRenderers/ListRenderer.cs

@@ -2,31 +2,82 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using Markdig.Syntax;
+using System.Globalization;
 using CommunityToolkit.Labs.WinUI.MarkdownTextBlock.TextElements;
+using Markdig.Syntax;
+using RomanNumerals;
 
 namespace CommunityToolkit.Labs.WinUI.MarkdownTextBlock.Renderers.ObjectRenderers;
 
 internal class ListRenderer : UWPObjectRenderer<ListBlock>
 {
+    public const string UnorderedListDot = "• ";
+
     protected override void Write(WinUIRenderer renderer, ListBlock listBlock)
     {
-        if (renderer == null) throw new ArgumentNullException(nameof(renderer));
-        if (listBlock == null) throw new ArgumentNullException(nameof(listBlock));
-
-        var list = new MyList(listBlock);
+        int index = 1;
+        bool isOrdered = false;
+        BulletType bulletType = BulletType.Circle;
+        if (listBlock.IsOrdered)
+        {
+            isOrdered = true;
+            bulletType = ToOrderedBulletType(listBlock.BulletType);
 
-        renderer.Push(list);
+            if (listBlock.OrderedStart != null && listBlock.DefaultOrderedStart != listBlock.OrderedStart)
+            {
+                int.TryParse(listBlock.OrderedStart, NumberStyles.Number, NumberFormatInfo.InvariantInfo, out index);
+            }
+        }
 
-        foreach (var item in listBlock)
+        bool parentIsFirstBulletItem = renderer.IsFirstBulletItem;
+        bool parentIsLastBulletItem = renderer.IsLastBulletItem;
+        renderer.IsFirstBulletItem = true;
+        renderer.IsLastBulletItem = listBlock.Count == 1;
+        foreach (var listItem in listBlock)
         {
-            var listItemBlock = (ListItemBlock)item;
-            var listItem = new MyBlockContainer(listItemBlock);
-            renderer.Push(listItem);
-            renderer.WriteChildren(listItemBlock);
-            renderer.Pop();
+            renderer.PushListBullet(GetBulletString(isOrdered, bulletType, index));
+            renderer.Write(listItem);
+            renderer.PopListBullet();
+            index++;
+
+            renderer.IsFirstBulletItem = false;
+            renderer.IsLastBulletItem = listBlock.Count == index;
         }
+        renderer.IsFirstBulletItem = parentIsFirstBulletItem;
+        renderer.IsLastBulletItem = parentIsLastBulletItem;
+    }
 
-        renderer.Pop();
+    internal static BulletType ToOrderedBulletType(char bullet)
+    {
+        return bullet switch
+        {
+            '1' => BulletType.Number,
+            'a' => BulletType.LowerAlpha,
+            'A' => BulletType.UpperAlpha,
+            'i' => BulletType.LowerRoman,
+            'I' => BulletType.UpperRoman,
+            _ => BulletType.Number,
+        };
+    }
+
+    private static string GetBulletString(bool isOrdered, BulletType bulletType, int index)
+    {
+        if (isOrdered)
+        {
+            return bulletType switch
+            {
+                BulletType.Number => $"{index}. ",
+                BulletType.LowerAlpha => $"{index.ToAlphabetical()}. ",
+                BulletType.UpperAlpha => $"{index.ToAlphabetical().ToUpper(CultureInfo.CurrentCulture)}. ",
+                BulletType.LowerRoman => $"{index.ToRomanNumerals().ToLower(CultureInfo.CurrentCulture)} ",
+                BulletType.UpperRoman => $"{index.ToRomanNumerals().ToUpper(CultureInfo.CurrentCulture)} ",
+                BulletType.Circle => UnorderedListDot,
+                _ => $"{index}. "
+            };
+        }
+        else
+        {
+            return UnorderedListDot;
+        }
     }
 }

components/MarkdownTextBlock/src/Renderers/ObjectRenderers/ParagraphRenderer.cs

@@ -14,7 +14,7 @@ protected override void Write(WinUIRenderer renderer, ParagraphBlock obj)
         if (renderer == null) throw new ArgumentNullException(nameof(renderer));
         if (obj == null) throw new ArgumentNullException(nameof(obj));
 
-        var paragraph = new MyParagraph(obj);
+        var paragraph = new MyParagraph(obj, renderer);
         // set style
         renderer.Push(paragraph);
         renderer.WriteLeafInline(obj);

components/MarkdownTextBlock/src/Renderers/WinUIRenderer.cs

@@ -17,6 +17,8 @@ public class WinUIRenderer : RendererBase
     private readonly Stack<IAddChild> _stack = new Stack<IAddChild>();
     private char[] _buffer;
     private MarkdownConfig _config = MarkdownConfig.Default;
+    private readonly Stack<string> _listBullets = new();
+
     public MyFlowDocument FlowDocument { get; private set; }
     public MarkdownConfig Config
     {
@@ -25,6 +27,10 @@ public MarkdownConfig Config
     }
     public MarkdownTextBlock MarkdownTextBlock { get; }
 
+    internal bool IsFirstBulletItem { get; set; }
+
+    internal bool IsLastBulletItem { get; set; }
+
     public WinUIRenderer(MyFlowDocument document, MarkdownConfig config, MarkdownTextBlock markdownTextBlock)
     {
         _buffer = new char[1024];
@@ -134,6 +140,29 @@ public void WriteText(string? text, int offset, int length)
         }
     }
 
+    public void PushListBullet(string bullet)
+    {
+        _listBullets.Push(bullet);
+    }
+
+    public string PeekListBullet()
+    {
+        return _listBullets.Count > 0 ? _listBullets.Peek() : string.Empty;
+    }
+
+    public int GetListBulletCount()
+    {
+        return _listBullets.Count;
+    }
+
+    public void PopListBullet()
+    {
+        if (_listBullets.Count > 0)
+        {
+            _listBullets.Pop();
+        }
+    }
+
     private static void AddInline(IAddChild parent, IAddChild inline)
     {
         parent.AddChild(inline);

components/MarkdownTextBlock/src/TextElements/BulletType.cs

@@ -0,0 +1,15 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace CommunityToolkit.Labs.WinUI.MarkdownTextBlock.TextElements;
+
+internal enum BulletType
+{
+    Circle,
+    Number,
+    LowerAlpha,
+    UpperAlpha,
+    LowerRoman,
+    UpperRoman
+}

components/MarkdownTextBlock/src/TextElements/MyList.cs

@@ -2,12 +2,14 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using CommunityToolkit.Labs.WinUI.MarkdownTextBlock.Renderers;
 using Markdig.Syntax;
 
 namespace CommunityToolkit.Labs.WinUI.MarkdownTextBlock.TextElements;
 
 internal class MyParagraph : IAddChild
 {
+    private readonly WinUIRenderer _renderer;
     private ParagraphBlock _paragraphBlock;
     private Paragraph _paragraph;
 
@@ -16,10 +18,27 @@ public TextElement TextElement
         get => _paragraph;
     }
 
-    public MyParagraph(ParagraphBlock paragraphBlock)
+    public MyParagraph(ParagraphBlock paragraphBlock, WinUIRenderer renderer)
     {
         _paragraphBlock = paragraphBlock;
         _paragraph = new Paragraph();
+        _renderer = renderer;
+
+        // Lists are plain Paragraph_s, one per item.
+        // This is so that you can select across list items.
+        Thickness margin = new Thickness(0, 8, 0, 8); // renderer.Config.Themes.BlockMargin;
+        int bulletCount = renderer.GetListBulletCount();
+        margin.Left += 30 * bulletCount;
+        _paragraph.Margin = margin;
+
+        if (bulletCount != 0)
+        {
+            string bullet = renderer.PeekListBullet();
+            Run bulletRun = new Run { Text = bullet + "\t" };
+
+            _paragraph.Inlines.Add(bulletRun);
+            _paragraph.TextIndent = -30;
+        }
     }
 
     public void AddChild(IAddChild child)