Accessor of the slot hexpand-set of the gtk-widget class.
The generic function gtk-widget-hexpand-set gets whether the generic function gtk-widget-hexpand has been used to explicitly set the expand flag on this widget.
If hexpand is set, then it overrides any computed expand value based on child widgets. If hexpand is not set, then the expand value depends on whether any children of the widget would like to expand.
There are few reasons to use this function, but it is here for completeness and consistency.
The hexpand-set property will be set automatically when you call the function gtk-widget-hexpand to set hexpand, so the most likely reason to use this function would be to unset an explicit expand flag.