Working with percentages in SwiftUI layout

public func relativeProposed ( width : Double = 1 , height : Double = 1 ) -> some View { RelativeSizeLayout ( relativeWidth : width , relativeHeight : height ) { // Wrap content view in a container to make sure the layout only // receives a single subview. This is because our layout only adjusts the proposed size for its subview but then accepts the subview’s actual size as its own. In this example, the layout’s subview is the frame(maxWidth: 400) view, which sets its own width to the proposed width or 400, whichever is smaller.