DY
Size of the vertical scrollbar's thumbnail in any unit.
Value
Any floating-point value greater than zero and smaller than the difference between YMAX and YMIN.
Default:: "0.1".
Notes
LINEY, YMAX and YMIN are only updated in the scrollbar when DY is updated.
When the canvas is visible, a change in DY can generate a redraw in the horizontal scrollbar on the screen.
A change in these values can affect the attribute POSY.