Gtk.Style.draw_box_gap:
Description:
public virtual void draw_box_gap (
Gdk.Window window,
Gtk.StateType state_type,
Gtk.ShadowType shadow_type,
Gdk.Rectangle area,
Gtk.Widget widget,
string detail,
int x,
int y,
int width,
int height,
Gtk.PositionType gap_side,
int gap_x,
int gap_width)