# onScrollTargetVisibilityChange(idType:threshold:_:) Adds an action to be called with information about what views would be considered visible. ``` nonisolated func onScrollTargetVisibilityChange(idType: ID.Type, threshold: Double = 0.5, _ action: @escaping ([ID]) -> Void) -> some View where ID : Hashable ``` ## Parameters `idType` The type of Identity provided by the subviews. `threshold` The amount required to be visible within the viewport of the the scrollview before the `action` is fired. By default when the view has crossed more than 50% on-screen, the action will be called. `action` The action which will be called when the views within the scroll view cross the provided threshold. The callback will include which views are considered visible. ## Discussion Use this modifier along with the modifier `View/scrollTargetLayout()` to be informed when the views in the targetted scroll view have crossed the provided threshold to be considered on/off screen. ``` ScrollView { LazyVStack { ForEach(models) { model in CardView(model: model) } } .scrollTargetLayout() } .onScrollTargetVisibilityChange(for: Model.ID.self, threshold: 0.2) { onScreenCards in // Disable video playback for cards that are offscreen... } ``` --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)