POSY
Thumbnail position in the vertical scrollbar in any unit.
Value
Any floating-point value. Must be a value between YMIN and YMAX-DY.
Default: "0.0"
Notes
When the canvas is visible, a change in POSY can generate a redraw in the vertical scrollbar on the screen.
This attribute does not generate a redraw of the canvas. If you need a redraw call IupUpdate.