MarkdownSelectableTextBlockA Avalonia.Controls.TextBlock that exposes hyperlink hit-testing and plain-text extraction for use by MarkdownViewer's pointer handling and selection layer registration. Does not own selection — that is managed by MarkView.Avalonia.Rendering.DocumentSelectionLayer. It can also draw a border along its edges (BorderBrush, BorderThickness), which a theme uses to rule off a heading.
MarkdownSelectionAttached properties through which renderers make non-text content (images, formulas, diagrams) take part in MarkdownViewer's document-wide text selection.
SlugGeneratorGenerates GitHub-style kebab-case anchor IDs from heading text. Tracks duplicates and appends -1, -2, etc. until the ID is unused, as GitHub does.
TaskToggledEventArgsEvent args for a task-list checkbox toggled by the user. Carries the new state and where the item's [ ] / [x] marker sits in the markdown source, so the host can write the change back.
ThemeTrackingKeeps content whose colours are baked in at render time (bitmaps, SVG, highlighted runs) in sync with the application theme. Standard controls follow theme changes on their own through DynamicResource; this covers content that must be rebuilt instead.
ViewportTrackingDefers costly content (a decoded image, a formula bitmap, highlighted code, a diagram) until the element that shows it is about to scroll into view, so the parts of a long document nobody reaches cost nothing. Renderers honour IsLazyRenderingEnabled before using it.