--- description: "Generates a WPF MarkdownPresenter: a ContentControl with a bindable Markdown dependency property that parses Markdig into a FlowDocument and hosts it in a selectable, content-hugging read-only RichTextBox. Use when rendering LLM/chat markdown output as selectable rich text in WPF, or when building a chat/markdown view. Usage: /wpf-dev-pack:make-wpf-markdown-presenter " argument-hint: [Name] --- # WPF Markdown Presenter Generator **If `$0` is empty, use the AskUserQuestion tool to ask: "Enter the presenter control name (e.g., MarkdownPresenter, ChatMarkdownView)". Do NOT proceed until a valid name is provided. Use the response as the control name for all subsequent steps.** Generate a `$0` control: a `ContentControl` with a bindable `Markdown` dependency property that parses markdown with Markdig, builds a WPF `FlowDocument`, and hosts it in a selectable, content-hugging read-only `RichTextBox`. - Replace `{Namespace}` with the project's root namespace detected from csproj or existing code. - Replace `{Project}` with the target project path (a WPF Application or WPF control library — must have `UseWPF`). > **The full rationale** for every choice below is in two knowledge topics — > fetch with `WpfDevPackMcp get_wpf_topic`: `rendering-markdown-in-wpf` (the > AST→FlowDocument dispatcher, the "never `ToString()` a node" rule, the > `Block`/`Inline` aliasing, Hyperlink scheme validation) and > `displaying-selectable-rich-text-in-wpf` (the read-only RichTextBox host, the > content-hugging `HuggingRichTextBox`, `MouseWheel` forwarding, streaming throttle). ## Usage ```bash /wpf-dev-pack:make-wpf-markdown-presenter MarkdownPresenter ``` ## Required Packages ```xml ``` - **Markdig** is required (markdown parsing). Verify the current version and the exact API surface with HandMirror before emitting (`inspect_nuget_package` / `inspect_nuget_package_type` on `Markdig`), since the AST node type names drive the `switch`. - The code uses the WPF-UI (`Wpf.Ui`) theme-brush keys `TextFillColorPrimaryBrush` / `TextFillColorSecondaryBrush` via `SetResourceReference`, and a `Wpf.Ui.Controls.Button` for the code-block Copy button. If WPF-UI is not installed, swap those for stock WPF (`SystemColors.ControlTextBrushKey` resource reference, and a plain `System.Windows.Controls.Button`). See `integrating-wpfui-fluent` for the brush keys. ## Generated Code ### $0.cs The three `using`-aliases at the top are **mandatory** — `Markdig.Syntax.Block` and `System.Windows.Documents.Block` (and the two `Inline` types) collide (CS0104), so both must be aliased in any file that both parses markdown and builds a `FlowDocument`. ```csharp using System.Diagnostics; using System.Globalization; using System.Windows; using System.Windows.Controls; using System.Windows.Documents; using System.Windows.Input; using System.Windows.Media; using System.Windows.Threading; using Markdig; using Markdig.Syntax; using Markdig.Syntax.Inlines; using MarkdigBlock = Markdig.Syntax.Block; // markdown AST node using MarkdigInline = Markdig.Syntax.Inlines.Inline; // markdown AST inline using FlowBlock = System.Windows.Documents.Block; // FlowDocument node namespace {Namespace}.Controls; /// /// A ContentControl that renders a bound Markdown string as a selectable WPF /// FlowDocument hosted in a read-only RichTextBox. Unhandled Markdig AST nodes /// are recursed (Container), degraded to inlines/lines (Leaf), or skipped — /// never ToString()'d (the default ToString returns the type name). /// public sealed class $0 : ContentControl { private static readonly MarkdownPipeline _pipeline = new MarkdownPipelineBuilder().UseAdvancedExtensions().Build(); public static readonly DependencyProperty MarkdownProperty = DependencyProperty.Register(nameof(Markdown), typeof(string), typeof($0), new PropertyMetadata(null, OnMarkdownChanged)); public string? Markdown { get => (string?)GetValue(MarkdownProperty); set => SetValue(MarkdownProperty, value); } // Coalesce re-renders during fast streaming instead of rebuilding per token. private readonly DispatcherTimer _renderTimer = new() { Interval = TimeSpan.FromMilliseconds(50) }; // ~20 Hz public $0() { _renderTimer.Tick += (_, _) => { _renderTimer.Stop(); Render(Markdown); }; } private static void OnMarkdownChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) { var self = ($0)d; self._renderTimer.Stop(); self._renderTimer.Start(); // debounce: render once the burst settles } // Render: parse markdown -> build a FlowDocument -> host it in a read-only RichTextBox. private void Render(string? markdown) { if (string.IsNullOrEmpty(markdown)) { Content = null; return; } var doc = new FlowDocument { PagePadding = new Thickness(0), FontSize = 14 }; foreach (MarkdigBlock block in Markdig.Markdown.Parse(markdown, _pipeline)) { FlowBlock? b = RenderBlock(block); if (b is not null) { doc.Blocks.Add(b); } } var host = new HuggingRichTextBox { Document = doc, IsReadOnly = true, // selection + Ctrl+C; no editing, no caret IsDocumentEnabled = true, // Hyperlink inlines stay clickable IsTabStop = false, BorderThickness = new Thickness(0), Background = Brushes.Transparent, Padding = new Thickness(0), MinHeight = 0, NaturalWidth = ComputeNaturalWidth(markdown) }; // Code-built text elements do NOT inherit a theme foreground — set it once. host.SetResourceReference(Control.ForegroundProperty, "TextFillColorPrimaryBrush"); ScrollViewer.SetHorizontalScrollBarVisibility(host, ScrollBarVisibility.Disabled); // wrap at forced width host.PreviewMouseWheel += ForwardWheelToParent; Content = host; } private FlowBlock? RenderBlock(MarkdigBlock block) => block switch { FencedCodeBlock c => BuildCodeBlock(c.Lines.ToString()), CodeBlock c => BuildCodeBlock(c.Lines.ToString()), HeadingBlock h => BuildHeading(h), ListBlock l => BuildList(l), QuoteBlock q => BuildQuote(q), ThematicBreakBlock => BuildThematicBreak(), ParagraphBlock p => BuildParagraph(p), ContainerBlock c => BuildContainerFallback(c), // recurse children into a Section LeafBlock leaf => BuildLeafFallback(leaf), // render its inlines/lines _ => null, // never emit a type name }; private Paragraph BuildParagraph(ParagraphBlock p) { var para = new Paragraph { Margin = new Thickness(0, 0, 0, 6) }; AppendInlines(para.Inlines, p.Inline); return para; } private Paragraph BuildHeading(HeadingBlock h) { var para = new Paragraph { FontWeight = FontWeights.Bold, FontSize = h.Level switch { 1 => 20, 2 => 17, 3 => 15, _ => 14 }, Margin = new Thickness(0, 0, 0, 6) }; AppendInlines(para.Inlines, h.Inline); return para; } private Section BuildQuote(QuoteBlock quote) { var section = new Section { BorderThickness = new Thickness(3, 0, 0, 0), // left accent rule Padding = new Thickness(8, 0, 0, 0), Margin = new Thickness(0, 0, 0, 6) }; section.SetResourceReference(TextElement.ForegroundProperty, "TextFillColorSecondaryBrush"); section.SetResourceReference(FlowBlock.BorderBrushProperty, "TextFillColorSecondaryBrush"); foreach (MarkdigBlock child in quote) { FlowBlock? r = RenderBlock(child); if (r is not null) { section.Blocks.Add(r); } } return section; } private List BuildList(ListBlock list) { var result = new List { MarkerStyle = list.IsOrdered ? TextMarkerStyle.Decimal : TextMarkerStyle.Disc, Margin = new Thickness(0, 0, 0, 6), Padding = new Thickness(16, 0, 0, 0) }; foreach (MarkdigBlock item in list) { var li = new ListItem(); if (item is ListItemBlock ib) { foreach (MarkdigBlock child in ib) { FlowBlock? r = RenderBlock(child); if (r is not null) { li.Blocks.Add(r); } } } if (li.Blocks.Count == 0) { li.Blocks.Add(new Paragraph(new Run(item.ToString() ?? string.Empty))); } result.ListItems.Add(li); } return result; } // Generic fallbacks — the anti-type-name-leak core: private Section BuildContainerFallback(ContainerBlock container) { var s = new Section(); foreach (MarkdigBlock child in container) { FlowBlock? r = RenderBlock(child); if (r is not null) { s.Blocks.Add(r); } } return s; } private Paragraph BuildLeafFallback(LeafBlock leaf) { var p = new Paragraph { Margin = new Thickness(0, 0, 0, 6) }; if (leaf.Inline is not null) { AppendInlines(p.Inlines, leaf.Inline); } else { p.Inlines.Add(new Run(leaf.Lines.ToString())); } return p; } // A horizontal rule. Minimal helper — adjust styling as needed. private static FlowBlock BuildThematicBreak() => new BlockUIContainer(new Separator { Margin = new Thickness(0, 4, 0, 4) }); private static BlockUIContainer BuildCodeBlock(string code) { string text = code.TrimEnd('\n', '\r'); var box = new TextBox { Text = text, IsReadOnly = true, FontFamily = new FontFamily("Consolas"), TextWrapping = TextWrapping.NoWrap, HorizontalScrollBarVisibility = ScrollBarVisibility.Auto, BorderThickness = new Thickness(0), Background = Brushes.Transparent }; box.SetResourceReference(TextBox.ForegroundProperty, "TextFillColorPrimaryBrush"); var copy = new Button { Content = "Copy", VerticalAlignment = VerticalAlignment.Top }; copy.Click += (_, _) => { try { Clipboard.SetText(text); } catch { /* clipboard busy */ } }; var grid = new Grid(); grid.ColumnDefinitions.Add(new ColumnDefinition { Width = new GridLength(1, GridUnitType.Star) }); grid.ColumnDefinitions.Add(new ColumnDefinition { Width = GridLength.Auto }); Grid.SetColumn(box, 0); Grid.SetColumn(copy, 1); grid.Children.Add(box); grid.Children.Add(copy); var border = new Border { Padding = new Thickness(8), Margin = new Thickness(0, 4, 0, 6), Child = grid }; return new BlockUIContainer(border) { Margin = new Thickness(0) }; } private void AppendInlines(InlineCollection target, ContainerInline? container) { if (container is null) { return; } foreach (MarkdigInline inline in container) { switch (inline) { case LiteralInline lit: target.Add(new Run(lit.Content.ToString())); break; case EmphasisInline em: Span span; if (em.DelimiterCount >= 2) { span = new Bold(); } else { span = new Italic(); } AppendInlines(span.Inlines, em); // nested formatting preserved target.Add(span); break; case CodeInline code: target.Add(new Run(code.Content) { FontFamily = new FontFamily("Consolas") }); break; case LinkInline link: var h = new Hyperlink { NavigateUri = SafeUri(link.Url) }; AppendInlines(h.Inlines, link); h.RequestNavigate += (s, e) => { OpenInBrowser(e.Uri); e.Handled = true; }; target.Add(h); break; case LineBreakInline: target.Add(new LineBreak()); break; default: if (inline is ContainerInline nested) { AppendInlines(target, nested); } break; // never add inline.ToString() } } } // Natural width is measured from the source markdown lines (reliable at any constraint). private static double ComputeNaturalWidth(string markdown) { var prose = new Typeface("Segoe UI"); var code = new Typeface("Consolas"); double max = 0; bool inFence = false; foreach (string line in markdown.Replace("\r\n", "\n").Split('\n')) { string t = line.TrimStart(); if (t.StartsWith("```")) { inFence = !inFence; continue; } if (line.Length == 0) { continue; } double size = 14; Typeface tf = prose; if (inFence) { tf = code; } else if (t.StartsWith("#")) { size = 20; } // heading rendered larger -> measure larger var ft = new FormattedText(line, CultureInfo.CurrentCulture, FlowDirection.LeftToRight, tf, size, Brushes.Black, 1.0); max = Math.Max(max, ft.WidthIncludingTrailingWhitespace); } return max + 12; // padding / caret / bold-and-inline-formatting buffer } // Read-only RichTextBox swallows MouseWheel; re-raise a bubbling MouseWheel on the parent. private static void ForwardWheelToParent(object sender, MouseWheelEventArgs e) { if (e.Handled) { return; } e.Handled = true; var args = new MouseWheelEventArgs(e.MouseDevice, e.Timestamp, e.Delta) { RoutedEvent = UIElement.MouseWheelEvent, Source = sender }; if (sender is RichTextBox host && host.Parent is UIElement parent) { parent.RaiseEvent(args); } } // Reject non-absolute URLs. Minimal helper. private static Uri? SafeUri(string? url) => Uri.TryCreate(url, UriKind.Absolute, out Uri? uri) ? uri : null; // Untrusted model output: allow http/https only before shell-executing a link. private static void OpenInBrowser(Uri? uri) { if (uri is null) { return; } if (uri.Scheme != Uri.UriSchemeHttp && uri.Scheme != Uri.UriSchemeHttps) { return; } // allow-list try { Process.Start(new ProcessStartInfo(uri.AbsoluteUri) { UseShellExecute = true }); } catch { /* a navigation failure must not crash the chat */ } } // A content-hugging read-only RichTextBox: a read-only RichTextBox cannot self-measure its // natural width (it collapses to ~0 at an infinite constraint and is greedy at a finite one), // so the natural width is computed externally (ComputeNaturalWidth) and forced here. private sealed class HuggingRichTextBox : RichTextBox { public double NaturalWidth { get; set; } protected override Size MeasureOverride(Size constraint) { double width = double.IsInfinity(constraint.Width) ? NaturalWidth : Math.Min(NaturalWidth, constraint.Width); // hug short / wrap long Size measured = base.MeasureOverride(new Size(width, constraint.Height)); return new Size(width, measured.Height); } } } ``` ### Optional: real table mapping `UseAdvancedExtensions()` parses pipe tables, but an unhandled `Table` falls through to the generic container fallback and renders as flat cell text. To promote it to a grid, add an arm to `RenderBlock`: ```csharp case Markdig.Extensions.Tables.Table mdTable: return BuildTable(mdTable); // Markdig TableRow/TableCell -> System.Windows.Documents.Table/TableRow/TableCell // BuildTable creates a WPF Table with one TableRowGroup; each TableCell hosts Paragraph(s) via AppendInlines. ``` ## XAML Usage ```xml ``` ## File Location ``` {Project}/ └── Controls/ └── $0.cs ``` ## Notes - **Theme foreground**: a `FlowDocument`/`TextBlock` built in code does not inherit a theme foreground (renders black on a dark theme). The single `SetResourceReference(Control.ForegroundProperty, ...)` on the host fixes it; children inherit it. - **Invalid theme keys throw at runtime, not build.** Referencing a non-existent `{ui:ThemeResource ...}`/resource key compiles and then throws `XamlParseException` on first render. Only use keys verified to exist in the kit. - `SafeUri`, `BuildThematicBreak` are minimal helpers — adjust to taste. ## Related - Knowledge (fetch via `WpfDevPackMcp get_wpf_topic`): `rendering-markdown-in-wpf`, `displaying-selectable-rich-text-in-wpf`, `integrating-wpfui-fluent`, `authoring-wpf-controls`. - Sibling scaffolders: this presenter is one of the pieces emitted by `/wpf-dev-pack:make-wpf-chatclient` (the one-button full chat client). Pair it with `/wpf-dev-pack:make-wpf-chat-bubble-template` to place it inside role-differentiated bubbles.