Selection Copy

Set enableSelection to enable source-backed selection. Box mode creates its selection host internally:

AnimatedStreamingMarkdown(
  blocks: result.blocks,
  enableSelection: true,
);

Use the optional controller when application code needs to observe or change the range:

final controller = AnimatedMarkdownSelectionController();

AnimatedStreamingMarkdown(
  blocks: result.blocks,
  enableSelection: true,
  selectionController: controller,
);

controller.selection = const TextSelection(
  baseOffset: 24,
  extentOffset: 8,
  isDirectional: true,
);

print(controller.value.selectedMarkdown);
controller.clear();
controller.selectAll();

Offsets are UTF-16 Markdown source offsets and retain their base/extent direction. The renderer clamps them to valid grapheme boundaries.

Sliver Selection

Sliver mode keeps lazy rendering and uses an explicit coordinator around the scroll view:

AnimatedStreamingMarkdownSelectionArea(
  controller: controller,
  scrollPadding: const EdgeInsets.all(20),
  child: CustomScrollView(
    slivers: [
      AnimatedStreamingMarkdown(
        blocks: result.blocks,
        asSliver: true,
        enableSelection: true,
        selectionController: controller,
      ),
    ],
  ),
);

One wrapper manages one Markdown renderer. A remounted sliver child receives its local selection from the controller source range immediately. Box mode does not need this wrapper.

The controller keeps the Markdown source snapshot and directional TextSelection as the authority. This means copy is not reconstructed from the currently mounted or visible widgets, which is important for lazy slivers and streamed content.

Supported copy behavior includes:

• Paragraphs and headings.
• Links as Markdown links.
• Lists and task lists.
• Block quotes.
• Code fences.
• Tables.
• HTML blocks.
• Footnote references and definitions.
• Callouts and front matter.
• Inline and block images.
• Inline and display LaTeX.

Clipboard Targets

selectionStrategy controls the payload:

• plain: rendered text with Markdown syntax removed.
• raw: the selected Markdown source.
• rich: HTML plus the same selection as plain text.

Rich copy is wired for every supported target:

Target	Rich clipboard representation
Web	Browser HTML selection copy plus plain text
Android	ClipData HTML and plain text
iOS	public.html and public.utf8-plain-text
macOS	NSPasteboard HTML and string types
Windows	HTML Format and CF_UNICODETEXT
Linux	GTK text/html and text/plain targets

Native and programmatic rich-copy operations always carry a plain-text fallback. If a desktop clipboard manager or native host rejects the HTML payload, the handler retries with plain text and does not expose UnsupportedError to the UI. Browser copy events provide both text/html and text/plain when the browser exposes writable clipboard data. Whether a receiving application chooses the HTML flavor is controlled by that host.

Stable Drag Selection

Selection endpoints are stored as absolute source offsets, then projected to the text rectangles currently on screen. This keeps a chosen range anchored while streaming appends content or an ancestor scrolls.

The renderer supports:

• A single continuous highlight layer per visual line, without per-token background shadows.
• Atomic selection over the real laid-out bounds of images and formulas, including touch long-press selection and handles.
• Partial text selection inside individual table cells.
• Dragging selection across a table into blocks above or below it.
• Vertical auto-scroll near a containing viewport edge.
• Horizontal auto-scroll near either edge of a wide table.
• Frame-by-frame edge scrolling with no fling after pointer-up or cancel.
• Programmatic and keyboard endpoint reveal using scrollPadding and the editable-text caret timing.
• Reverse-axis and RTL-aware scroll directions.

During a drag, the touched block leases its layout snapshot. Streaming can continue elsewhere; if that block changes, its endpoints remap to the new projection when the gesture ends.

Keyboard shortcuts, context menus, browser copy events, and mobile toolbars all derive their payload from the controller source range. Selection stays stable while tokens settle or a streamed block is replaced; the active block leases its geometry during a drag and remaps endpoints after the gesture completes.

On web and desktop, a deliberate primary click elsewhere inside the application dismisses a finalized range. Scrolling, changing browser tabs, and switching windows do not clear it; the selection remains available when focus returns. Refocus the renderer before using the browser keyboard-copy shortcut because copy-event interception is focus-dependent. If an endpoint leaves the viewport, its handle is hidden until that endpoint is visible again while the source range itself remains unchanged.

See Roadmap for the current planning notes.