SwiftUI add inverted mask

Question

I\'m trying to add a mask to two shapes such that the second shape masks out the first shape. If I do something like Circle().mask(Circle().offset(…)), this has

Answer 1

I haven't tested this yet, but could you do something like this:

extension UIView {
    func mask(_ rect: CGRect, invert: Bool = false) {
        let maskLayer = CAShapeLayer()
        let path = CGMutablePath()

        if (invert) {
            path.addRect(bounds)
        }
        path.addRect(rect)
        maskLayer.path = path

        if (invert) {
            maskLayer.fillRule = CAShapeLayerFillRule.evenOdd
        }

        // Set the mask of the view.
        layer.mask = maskLayer
    }
}

struct MaskView: UIViewRepresentable {
    @Binding var child: UIHostingController
    @Binding var rect: CGRect
    @Binding var invert: Bool

    func makeUIView(context: UIViewRepresentableContext) -> UIView {
        let view = UIView()

        self.child.view.mask(self.rect, invert: self.invert)

        view.addSubview(self.child.view)

        return view
    }

    func updateUIView(_ uiView: UIView, context: UIViewRepresentableContext) {

    }
}

Usage:

struct ImageView: View {
    var body: some View {
        Image("image1")
    }
}

struct ContentView: View {
    @State var child = UIHostingController(rootView: ImageView())
    @State var rect: CGRect = CGRect(x: 50, y: 50, width: 50, height: 50)
    @State var invert: Bool = false

    var body: some View {
        VStack(alignment: .leading) {
            MaskView(child: self.$child, rect: self.$rect, invert: self.$invert)
        }
    }
}