Support watchOS to use digital crown for the zooming image

Author: dreampiggy

Example/SDWebImageSwiftUIDemo/DetailView.swift

@@ -15,34 +15,62 @@ struct DetailView: View {
     @State var isAnimating: Bool = true
     @State var lastScaleValue: CGFloat = 1.0
     @State var scale: CGFloat = 1.0
+    @Environment(\.presentationMode) var presentationMode
 
     var body: some View {
         VStack {
             #if os(iOS) || os(tvOS)
             if animated {
-                contentView()
+                zoomView()
                 .navigationBarItems(trailing: Button(isAnimating ? "Stop" : "Start") {
                     self.isAnimating.toggle()
                 })
             } else {
-                contentView()
+                zoomView()
             }
             #endif
             #if os(macOS) || os(watchOS)
             if animated {
-                contentView()
+                zoomView()
                 .contextMenu {
                     Button(isAnimating ? "Stop" : "Start") {
                         self.isAnimating.toggle()
                     }
                 }
             } else {
-                contentView()
+                zoomView()
             }
             #endif
         }
     }
 
+    func zoomView() -> some View {
+        #if os(macOS) || os(iOS) || os(tvOS)
+        return contentView()
+            .scaleEffect(self.scale)
+                .gesture(MagnificationGesture(minimumScaleDelta: 0.1).onChanged { value in
+                let delta = value / self.lastScaleValue
+                self.lastScaleValue = value
+                let newScale = self.scale * delta
+                self.scale = min(max(newScale, 0.5), 2)
+            }.onEnded { value in
+                self.lastScaleValue = 1.0
+            })
+        #else
+        return contentView()
+            // SwiftUI's bug workaround (watchOS 6.1)
+            // If use `.focusable(true)` here, after pop the Detail view, the Content view's List does not get focus again
+            // After some debug, I found that the pipeline to change focus becomes:
+            // Detail Pop (resign focus) -> Content Appear (List view become focus) -> Detail Disappear (become focus again) -> End
+            // Even you use `onDisappear`, it's too late because `.focusable` is called firstly
+            // Sadly, Content view's List focus is managed by SwiftUI (a UICollectionView actually), call `focusable` on Content view does nothing as well
+            // So, here we must use environment or binding, to not become focus during pop :)
+            .focusable(self.presentationMode.wrappedValue.isPresented)
+            .scaleEffect(self.scale)
+            .digitalCrownRotation($scale, from: 0.5, through: 2, by: 0.1, sensitivity: .low, isHapticFeedbackEnabled: false)
+        #endif
+    }
+    
     func contentView() -> some View {
         HStack {
             if animated {
@@ -74,15 +102,6 @@ struct DetailView: View {
                 #endif
             }
         }
-        .scaleEffect(self.scale)
-        .gesture(MagnificationGesture().onChanged { value in
-            let delta = value / self.lastScaleValue
-            self.lastScaleValue = value
-            let newScale = self.scale * delta
-            self.scale = min(max(newScale, 0.5), 2)
-        }.onEnded { value in
-            self.lastScaleValue = 1.0
-        })
     }
 }