Added basic UIKit Sheet functionality and preparation for presentation modification

Author: MiaKoring

Examples/Sources/WindowingExample/WindowingApp.swift

@@ -87,6 +87,7 @@ struct SheetDemo: View {
         .sheet(isPresented: $isShortTermSheetPresented) {
             Text("I'm only here for 5s")
                 .padding(20)
+                .presentationCornerRadius(2)
         }
     }
 
@@ -162,23 +163,24 @@ struct WindowingApp: App {
                 }
             }
         }
-
-        WindowGroup("Secondary window") {
-            #hotReloadable {
-                Text("This a secondary window!")
-                    .padding(10)
+        #if !os(iOS)
+            WindowGroup("Secondary window") {
+                #hotReloadable {
+                    Text("This a secondary window!")
+                        .padding(10)
+                }
             }
-        }
-        .defaultSize(width: 200, height: 200)
-        .windowResizability(.contentMinSize)
+            .defaultSize(width: 200, height: 200)
+            .windowResizability(.contentMinSize)
 
-        WindowGroup("Tertiary window") {
-            #hotReloadable {
-                Text("This a tertiary window!")
-                    .padding(10)
+            WindowGroup("Tertiary window") {
+                #hotReloadable {
+                    Text("This a tertiary window!")
+                        .padding(10)
+                }
             }
-        }
-        .defaultSize(width: 200, height: 200)
-        .windowResizability(.contentMinSize)
+            .defaultSize(width: 200, height: 200)
+            .windowResizability(.contentMinSize)
+        #endif
     }
 }

Sources/AppKitBackend/AppKitBackend.swift

@@ -1734,6 +1734,10 @@ public final class AppKitBackend: AppBackend {
             NSApplication.shared.stopModal()
         }
     }
+
+    public func setPresentationCornerRadius(of sheet: NSCustomSheet, to radius: Int) {
+        print("setting Sheet Corner Radius is unavailable on macOS and will be ignored")
+    }
 }
 
 public final class NSCustomSheet: NSCustomWindow, NSWindowDelegate {

Sources/SwiftCrossUI/Backend/AppBackend.swift

@@ -633,6 +633,27 @@ public protocol AppBackend: Sendable {
     /// Gets used by the SCUI sheet implementation to close a sheet.
     func dismissSheet(_ sheet: Sheet, window: Window?)
 
+    /// Sets the corner radius for a sheet presentation.
+    ///
+    /// This method is called when the sheet content has a `presentationCornerRadius` modifier
+    /// applied at its top level. The corner radius affects the sheet's presentation container,
+    /// not the content itself.
+    ///
+    /// - Parameters:
+    ///   - sheet: The sheet to apply the corner radius to.
+    ///   - radius: The corner radius in pixels.
+    func setPresentationCornerRadius(of sheet: Sheet, to radius: Int)
+
+    /// Sets the available detents (heights) for a sheet presentation.
+    ///
+    /// This method is called when the sheet content has a `presentationDetents` modifier
+    /// applied at its top level. Detents allow users to resize the sheet to predefined heights.
+    ///
+    /// - Parameters:
+    ///   - sheet: The sheet to apply the detents to.
+    ///   - detents: An array of detents that the sheet can be resized to.
+    func setPresentationDetents(of sheet: Sheet, to detents: [PresentationDetent])
+
     /// Presents an 'Open file' dialog to the user for selecting files or
     /// folders.
     ///
@@ -1215,4 +1236,12 @@ extension AppBackend {
     public func dismissSheet(_ sheet: Sheet, window: Window?) {
         todo()
     }
+
+    public func setPresentationCornerRadius(of sheet: Sheet, to radius: Int) {
+        todo()
+    }
+
+    public func setPresentationDetents(of sheet: Sheet, to detents: [PresentationDetent]) {
+        todo()
+    }
 }

Sources/SwiftCrossUI/Values/PresentationDetent.swift

@@ -0,0 +1,16 @@
+/// Represents the available detents (heights) for a sheet presentation.
+public enum PresentationDetent: Sendable, Hashable {
+    /// A detent that represents a medium height sheet.
+    case medium
+
+    /// A detent that represents a large (full-height) sheet.
+    case large
+
+    /// A detent at a custom fractional height of the available space.
+    /// - Parameter fraction: A value between 0 and 1 representing the fraction of available height.
+    case fraction(Double)
+
+    /// A detent at a specific fixed height in pixels.
+    /// - Parameter height: The height in pixels.
+    case height(Int)
+}

Sources/SwiftCrossUI/ViewGraph/PreferenceValues.swift

@@ -2,13 +2,27 @@ import Foundation
 
 public struct PreferenceValues: Sendable {
     public static let `default` = PreferenceValues(
-        onOpenURL: nil
+        onOpenURL: nil,
+        presentationDetents: nil,
+        presentationCornerRadius: nil
     )
 
     public var onOpenURL: (@Sendable @MainActor (URL) -> Void)?
 
-    public init(onOpenURL: (@Sendable @MainActor (URL) -> Void)?) {
+    /// The available detents for a sheet presentation. Only applies to the top-level view in a sheet.
+    public var presentationDetents: [PresentationDetent]?
+
+    /// The corner radius for a sheet presentation. Only applies to the top-level view in a sheet.
+    public var presentationCornerRadius: Int?
+
+    public init(
+        onOpenURL: (@Sendable @MainActor (URL) -> Void)?,
+        presentationDetents: [PresentationDetent]? = nil,
+        presentationCornerRadius: Int? = nil
+    ) {
         self.onOpenURL = onOpenURL
+        self.presentationDetents = presentationDetents
+        self.presentationCornerRadius = presentationCornerRadius
     }
 
     public init(merging children: [PreferenceValues]) {
@@ -21,5 +35,10 @@ public struct PreferenceValues: Sendable {
                 }
             }
         }
+
+        // For presentation modifiers, take the first (top-level) value only
+        // This ensures only the root view's presentation modifiers apply to the sheet
+        presentationDetents = children.first?.presentationDetents
+        presentationCornerRadius = children.first?.presentationCornerRadius
     }
 }

Sources/SwiftCrossUI/Views/Modifiers/SheetModifier.swift

@@ -78,6 +78,9 @@ struct SheetModifier<Content: View, SheetContent: View>: TypeSafeView {
                 dryRun: true
             )
 
+            // Extract preferences from the sheet content
+            let preferences = dryRunResult.preferences
+
             let sheetSize = dryRunResult.size.idealSize
 
             let _ = children.sheetContentNode.update(
@@ -94,6 +97,16 @@ struct SheetModifier<Content: View, SheetContent: View>: TypeSafeView {
                 content: children.sheetContentNode.widget.into(),
                 onDismiss: handleDismiss
             )
+
+            // Apply presentation preferences to the sheet
+            if let cornerRadius = preferences.presentationCornerRadius {
+                backend.setPresentationCornerRadius(of: sheet, to: cornerRadius)
+            }
+
+            if let detents = preferences.presentationDetents {
+                backend.setPresentationDetents(of: sheet, to: detents)
+            }
+
             backend.showSheet(
                 sheet,
                 window: .some(environment.window! as! Backend.Window)

Sources/SwiftCrossUI/Views/Modifiers/Style/PresentationCornerRadiusModifier.swift

@@ -0,0 +1,19 @@
+//
+//  PresentationCornerRadiusModifier.swift
+//  swift-cross-ui
+//
+//  Created by Mia Koring on 03.10.25.
+//
+
+extension View {
+    /// Sets the corner radius for a sheet presentation.
+    ///
+    /// This modifier only affects the sheet presentation itself when applied to the
+    /// top-level view within a sheet. It does not affect the content's corner radius.
+    ///
+    /// - Parameter radius: The corner radius in pixels.
+    /// - Returns: A view with the presentation corner radius preference set.
+    public func presentationCornerRadius(_ radius: Int) -> some View {
+        preference(key: \.presentationCornerRadius, value: radius)
+    }
+}

Sources/SwiftCrossUI/Views/Modifiers/Style/PresentationDetentsModifier.swift

@@ -0,0 +1,13 @@
+extension View {
+    /// Sets the available detents (heights) for a sheet presentation.
+    ///
+    /// This modifier only affects the sheet presentation itself when applied to the
+    /// top-level view within a sheet. It allows users to resize the sheet to different
+    /// predefined heights.
+    ///
+    /// - Parameter detents: A set of detents that the sheet can be resized to.
+    /// - Returns: A view with the presentation detents preference set.
+    public func presentationDetents(_ detents: Set<PresentationDetent>) -> some View {
+        preference(key: \.presentationDetents, value: Array(detents))
+    }
+}

Sources/UIKitBackend/UIKitBackend+Sheet.swift

@@ -0,0 +1,44 @@
+import SwiftCrossUI
+import UIKit
+
+extension UIKitBackend {
+    public typealias Sheet = CustomSheet
+
+    public func createSheet() -> CustomSheet {
+        let sheet = CustomSheet()
+        sheet.modalPresentationStyle = .formSheet
+        //sheet.transitioningDelegate = CustomSheetTransitioningDelegate()
+
+        return sheet
+    }
+
+    public func updateSheet(_ sheet: CustomSheet, content: Widget, onDismiss: @escaping () -> Void)
+    {
+        sheet.view = content.view
+        sheet.onDismiss = onDismiss
+    }
+
+    public func showSheet(_ sheet: CustomSheet, window: UIWindow?) {
+        var topController = window?.rootViewController
+        while let presented = topController?.presentedViewController {
+            topController = presented
+        }
+        topController?.present(sheet, animated: true)
+    }
+
+    public func dismissSheet(_ sheet: CustomSheet, window: UIWindow?) {
+        sheet.dismiss(animated: true)
+    }
+}
+
+public final class CustomSheet: UIViewController {
+    var onDismiss: (() -> Void)?
+
+    public override func viewDidLoad() {
+        super.viewDidLoad()
+    }
+
+    public override func viewDidDisappear(_ animated: Bool) {
+        onDismiss?()
+    }
+}