takesFocusFrom property
A node above the page that takes focus without wanting the keys: the page shell's selection area, which takes focus on every click into the text. Focus on it passes here, beneath it, so a click into a paragraph leaves the page as it was before the click -- Page Down scrolls, Esc is the page's to answer -- and the selection stays, because focus is still inside the area that holds it.
Implementation
final FocusNode? takesFocusFrom;