/// returns the row near the specified y-coordinate in a given paragraph
/// (relative to the screen). If assert_in_view is true, it is made sure
/// that the row is on screen completely; this might change the given pit.
/// returns the row near the specified y-coordinate in a given paragraph
/// (relative to the screen). If assert_in_view is true, it is made sure
/// that the row is on screen completely; this might change the given pit.