Source Mapping and Hit Testing

Every rendered text segment and rich control is mapped back to a Markdig AST node and source span. Use this for hover highlights, source-editor synchronization, inspection tools, context commands, and custom editing gestures.

Hit test a point

var point = pointerEvent.GetPosition(markdownView);
var hit = markdownView.HitTestMarkdown(point);

if (hit is not null)
{
    var source = hit.SourceSpan.Slice(hit.ParseResult.OriginalMarkdown);
    ShowSourceRange(hit.SourceSpan.Start, hit.SourceSpan.Length);
    ShowHighlight(hit.HighlightRects);
}

MarkdownHitTestResult exposes:

Property	Meaning
`AstNode`	Node object, node kind, source span, line, and column.
`SourceSpan`	Effective source range, including a plugin override when supplied.
`MatchedSourceText`	The effective span sliced from the original source.
`ElementKind`	Text, line break, inline control, or block control.
`RenderedTextPosition`	Position in the rendered text stream when applicable.
`Visual`	Rich control associated with the hit, when applicable.
`HighlightRects`	Control-relative rectangles suitable for a hover overlay.
`HighlightBounds`	Union of the highlight rectangles, when any exist.
`ParseResult`	The source document and AST parent map used for the render.

Source spans

MarkdownSourceSpan uses a zero-based Start and a Length. End is inclusive, while EndExclusive is suitable for ranges and slicing. Empty has no valid range. Use Contains, Slice, or FromMarkdig instead of repeating boundary calculations.

Parser plugins can transform source before Markdig parses it. MarkdownParseResult.UsesOriginalSourceSpans is true only when parsed and original source are identical. Extensions that transform source must preserve offsets or provide accurate custom AST spans if consumers depend on editing or selection.

Inspect the latest render

MarkdownTextBlock.LastRenderMap contains:

TextEntries — rendered text ranges mapped to AST nodes and element kinds
VisualEntries — rich Avalonia controls mapped to AST nodes and optional plugin hit-test handlers

Use TryGetTextEntry or TryGetVisualEntry for direct lookup. LastParseResult.ParentMap and TryGetParent let tools walk from an inline node to its enclosing block.

Service-level hit testing

IMarkdownHitTestingService.HitTestTextPosition maps a rendered-text position without requiring a pointer:

var result = markdownView.LastRenderResult;
if (result is not null)
{
    var hit = markdownView.HitTestingService.HitTestTextPosition(result, textPosition);
}

Custom render controls can call IMarkdownHitTestingService.HitTest with a MarkdownHitTestRequest containing the host, point, render result, text layout, and padding. MarkdownTextBlock.HitTestMarkdown already supplies those details.