A presentation style that displays the content centered in the screen smaller than a regular sheet.

FormSheet.swift

import SwiftUI

extension View {
    
    /// Presents a form sheet when a binding to a Boolean value that you provide is true.
    /// - Parameters:
    ///   - isPresented: A binding to a Boolean value that determines whether
    ///     to present the sheet that you create in the modifier's
    ///     `content` closure.
    ///   - interactiveDismiss: A Boolean value that indicates whether to 
    ///     prevent nonprogrammatic dismissal.
    ///   - content: A closure that returns the content of the sheet.
    public func formSheet<Content>(
        isPresented: Binding<Bool>,
        interactiveDismiss: Bool = true,
        @ViewBuilder content: @escaping () -> Content
    ) -> some View where Content : View {
        self.background {
            FormSheetPresentable(
                isPresenting: isPresented,
                interactiveDismiss: interactiveDismiss,
                content: content
            )
        }
    }
}

fileprivate struct FormSheetPresentable<Content>: UIViewControllerRepresentable where Content : View {
    
    @Binding var isPresenting: Bool
    let interactiveDismiss: Bool
    @ViewBuilder let content: () -> Content
    @State private var contentViewController: UIViewController?
    
    func makeUIViewController(context: Context) -> some UIViewController {
        UIViewController()
    }
    
    func updateUIViewController(_ viewController: UIViewControllerType, context: Context) {
        if isPresenting {
            guard self.contentViewController == nil else {
                return
            }
            let contentViewController = makeContentViewController()
            contentViewController.presentationController?.delegate = context.coordinator
            viewController.present(contentViewController, animated: true)
            contentViewController.isModalInPresentation = !interactiveDismiss
            setContentViewController(contentViewController)
        } else {
            guard let contentViewController else {
                return
            }
            contentViewController.dismiss(animated: true)
            setContentViewController(nil)
        }
    }
    
    func setContentViewController(_ viewController: UIViewController?) {
        DispatchQueue.main.async {
            self.contentViewController = viewController
        }
    }

    func makeContentViewController() -> UIViewController {
        let viewController = UIHostingController(rootView: content())
        viewController.modalPresentationStyle = .formSheet
        return viewController
    }
    
    func makeCoordinator() -> Coordinator {
        Coordinator(self)
    }
}

extension FormSheetPresentable {
    
    class Coordinator: NSObject, UIAdaptivePresentationControllerDelegate {
        
        let parent: FormSheetPresentable
        
        init(_ parent: FormSheetPresentable) {
            self.parent = parent
        }
        
        func presentationControllerDidDismiss(_ presentationController: UIPresentationController) {
            self.parent.isPresenting = false
            self.parent.contentViewController = nil
        }
    }
}

struct FormSheetPreview: View {
    
    @State private var show = false
    
    var body: some View {
        Button {
            show.toggle()
        } label: {
            Text("\(show ? "Hide" : "Show") Sheet")
        }
        .formSheet(isPresented: $show) {
            Text("Hello there")
        }
    }
}

#Preview {
    FormSheetPreview()
}