func (b *Box) Fill(container *Box) {
	b.frame.X = container.inner.X
	b.frame.Y = container.inner.Y
	b.frame.W = container.inner.W
	b.frame.H = container.inner.H
}
Place a Box so that it fills the entire given container.
package main
type Rect struct {
	X int
	Y int
	W int
	H int
}
type Box struct {
	frame *Rect  
	inner *Rect  
}
func NewBox() *Box {
	return &Box{&Rect{0, 0, 0, 0}, &Rect{0, 0, 0, 0}}
}
func (b *Box) Center(container *Box) {
	widthleftover := container.inner.W - b.frame.W
	heightleftover := container.inner.H - b.frame.H
	b.frame.X = container.inner.X + widthleftover/2
	b.frame.Y = container.inner.Y + heightleftover/2
}