let scroll_link_canvas (sb : Widget.scrollbar Widget.widget) (lst : Widget.canvas Widget.widget) (orientation : string) : unit =
if(orientation="horizontal") then(
Canvas.configure ~xscrollcommand:(Scrollbar.set sb;) lst;
Scrollbar.configure ~command:(Canvas.xview lst) sb )
else (Canvas.configure ~yscrollcommand:(Scrollbar.set sb) lst;
Scrollbar.configure ~command:(Canvas.yview lst) sb)