How to popup on top of parent view without affecting parent's size?

The popup works. But when it pops up, it increases the parent view width and height as well (parent is smaller than pop-up and it's a requirement that parent to be smaller than pop-up). I want the popup to be an independent view. The popup should not affect the size of the parent. How to do that?

import SwiftUI

struct ParentView: View {


    @State private var WidgetSelectionShowState: Bool = false


    var body: some View {
        //Color.purple
        ZStack {

            Rectangle ()
                .fill(.blue)
                .zIndex(0) //
        Button ("show", action:  {

            withAnimation {
            WidgetSelectionShowState.toggle()
            }
                })

        if (WidgetSelectionShowState) {

            popupPage ()

        }
} .frame(width: 300, height: 100, alignment: .center)

    }
}


struct popupPage: View {


    var body: some View {
        ZStack {
        Text("This is a popup")


            Rectangle ()
                .fill(.green)
                .zIndex(0) //this is the layer order.

        }.transition(.asymmetric(insertion: .scale, removal: .opacity))
            . frame(width: 200, height: 500, alignment: .center )

}
}