The GTK.VScale widget is used to allow the user to select a value
using a vertical slider. A GtkAdjustment is used to set the initial
value, the lower and upper bounds, and the step and page
increments.
The position to show the current value, and the number of decimal
places shown can be set using the parent W(Scale) class's
functions.
GTK.Vscale(GTK.Adjustment())->set_usize(30,100)