func newContainer(child Control) *container {
c := new(container)
c.id = C.newContainerView(unsafe.Pointer(c))
c.child = child
c.child.setParent(&controlParent{c.id})
return c
}
// containerResized() gets called early so we have to do this in the constructor
func newContainer(resize func(x int, y int, width int, height int, d *sizing)) *container {
c := new(container)
c.resize = resize
c.id = C.newContainerView(unsafe.Pointer(c))
return c
}