SwiftUI preview landscape view modifier

gistfile1.swift

struct LandscapeModifier: ViewModifier {
    func body(content: Content) -> some View {
        content
            .previewLayout(.fixed(width: 812, height: 375))
            .environment(\.horizontalSizeClass, .compact)
            .environment(\.verticalSizeClass, .compact)
    }
}

extension View {
    func landscape() -> some View {
        self.modifier(LandscapeModifier())
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
            .landscape()
    }
}