The new initarg
allows you to specify whether a
has tick marks, and how the tick marks are spaced. In LispWorks 6.0 and earlier versions, slider tick marks do not appear on all platforms, and there is no control over them in CAPI.
On Microsoft Windows and GTK+, the new initarg
allow you to control how the slider displays its current value.
LispWorks Release Notes and Installation Guide - 23 Dec 2011