Function gdk4_sys::gdk_popup_layout_set_shadow_width

pub unsafe extern "C" fn gdk_popup_layout_set_shadow_width(
    layout: *mut GdkPopupLayout, 
    left: c_int, 
    right: c_int, 
    top: c_int, 
    bottom: c_int
)

This is supported on crate feature v4_2 only.