Merge pull request #23 from Econa77/fix-ios17-lazy-content

Fix jittery views when Lazy-loaded content is present in iOS 17

Author: gh123man

Examples/ContentView.swift

@@ -84,6 +84,8 @@ struct DetailsView: View {
     @State var refreshed = 0
     var style: Style
     @State var useImage = true
+    let rectangles = (0..<50).map { _ in CGFloat.random(in: 10..<50) }
+
     var body: some View {
         ScrollView {
             VStack {
@@ -94,6 +96,25 @@ struct DetailsView: View {
                 }
                 Text("Details!")
                 Text("Refreshed: \(refreshed)")
+
+                ScrollView(.horizontal, showsIndicators: false) {
+                    LazyHStack(spacing: 8) {
+                        ForEach(0..<10) { _ in
+                            Rectangle()
+                                .frame(width: 100, height: 100)
+                        }
+                    }
+                    .padding(.horizontal)
+                }
+                LazyVGrid(columns: Array(repeating: GridItem(.flexible(), spacing: 8), count: 3)) {
+                    ForEach(rectangles, id: \.self) { size in
+                        VStack {
+                            Rectangle()
+                                .frame(width: size, height: size)
+                            Text("text")
+                        }
+                    }
+                }
             }
         }
         .refresher(style: style) {

Sources/Refresher/OffsetReader.swift

@@ -3,19 +3,23 @@ import SwiftUI
 
 struct OffsetReader: View {
     var onChange: (CGFloat) -> ()
-    @State private var frame = CGRect()
 
     public var body: some View {
         GeometryReader { geometry in
-            Spacer(minLength: 0)
-                .onChange(of: geometry.frame(in: .global)) { value in
-                    if value.integral != self.frame.integral {
-                        DispatchQueue.main.async {
-                            self.frame = value
-                            onChange(value.minY)
-                        }
-                    }
+            Color.clear
+                .preference(key: OffsetPreferenceKey.self,
+                            value: geometry.frame(in: .global).minY)
+                .onPreferenceChange(OffsetPreferenceKey.self) { offset in
+                    onChange(offset)
                 }
         }
     }
 }
+
+private struct OffsetPreferenceKey: PreferenceKey {
+    static var defaultValue = CGFloat.zero
+
+    static func reduce(value: inout CGFloat, nextValue: () -> CGFloat) {
+        value = nextValue()
+    }
+}