SmoothSelectionRegion class

A thin SelectableRegion adapter that exposes programmatic selection control.

The widget keeps Flutter's built-in selection overlay, gestures, shortcuts, handles, magnifier, and toolbar. It adds a stable controller/state surface for selecting all content, selecting a word or paragraph at a press position, and dispatching lower-level SelectionEvents to the underlying SelectionContainer.

Example:

final controller = SmoothSelectionController();

SmoothMarkdown(
  data: markdownText,
  selectable: true,
  selectionController: controller,
)

// Programmatic select-all (shows handles + toolbar):
controller.selectAll(SelectionChangedCause.toolbar);

// Lower-level: dispatch an arbitrary SelectionEvent straight to the
// SelectionContainer (fans out to every text selectable). Does not, by
// itself, drive the overlay.
controller.dispatchEvent(const SelectAllSelectionEvent());