Returns a real number between 0 and 1 indicating where the point given
by x and y lies in the trough area of the scrollbar, where 0.0
corresponds to the top or left of the trough and 1.0 corresponds to the
bottom or right. X and y are pixel coordinates relative to the scrollbar
widget. If x and y refer to a point outside the trough, the closest
point in the trough is used.
Returns a real number between 0 and 1 indicating where the point given by x and y lies in the trough area of the scrollbar, where 0.0 corresponds to the top or left of the trough and 1.0 corresponds to the bottom or right. X and y are pixel coordinates relative to the scrollbar widget. If x and y refer to a point outside the trough, the closest point in the trough is used.