listless

ListlessMac/Helpers/PlatformScrollIndicatorsModifier.swift (1338B)

1import SwiftUI
2
3private struct ContentHeightKey: PreferenceKey {
4    static let defaultValue: CGFloat = 0
5
6    static func reduce(value: inout CGFloat, nextValue: () -> CGFloat) {
7        value = max(value, nextValue())
8    }
9}
10
11private struct PlatformScrollIndicatorsModifier: ViewModifier {
12    let verticalPadding: CGFloat
13    @State private var contentHeight: CGFloat = 0
14
15    func body(content: Content) -> some View {
16        GeometryReader { proxy in
17            let effectiveContentHeight = max(0, contentHeight - (verticalPadding * 2))
18            content
19                .background(
20                    GeometryReader { contentProxy in
21                        Color.clear.preference(
22                            key: ContentHeightKey.self, value: contentProxy.size.height)
23                    }
24                )
25                .scrollIndicators(effectiveContentHeight > proxy.size.height ? .visible : .hidden)
26                .onPreferenceChange(ContentHeightKey.self) { height in
27                    if height != contentHeight {
28                        contentHeight = height
29                    }
30                }
31        }
32    }
33}
34
35extension View {
36    func platformScrollIndicators(verticalPadding: CGFloat = 0) -> some View {
37        modifier(PlatformScrollIndicatorsModifier(verticalPadding: verticalPadding))
38    }
39}