
This widget provides an X-Y intersection that follows a click or drag.

The FLTK documentation says:
"It would be useful if this could be put atop another widget so that the
crosshairs are on top, but this is not implemented."

I suppose it could be used to control the position of an object that is
in a different widget, but at this time I'm having a hard time visualizing
exactly what that use would be.
