gtk:scale-set-format-value-func (scale func)

scale -- a gtk:scale widget
func -- a gtk:scale-format-value-func callback function that formats the value

The func callback function allows you to change how the scale value is displayed. The given function will return a string representing the value. That string will then be used to display the value of the scale.

If nil is passed as func, the value will be displayed on its own, rounded according to the value of the digits property.