问How to track the mouse scroll event？

提问于 2023-05-04 13:15:46

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I'm trying to scale the `view`(zoom in and out) when the user scroll from the mouse after hovering the view. So, since I want to track scroll event across the application, I placed the following code in the root. But I don't know how to use it in the view.

**View**

import SwiftUI
struct ContentView: View {
      
    @State var recColour: Color = .black
    @State var scaleby = 2.0
  
        var body: some View {
        VStack (alignment: .leading){
           
            ZStack {
                    Rectangle()
                    .fill(.gray)
                    .frame(width: 100, height: 100)
                                  }
                            }
            .scaleEffect(scaleby)
            .onTapGesture {
                withAnimation {scaleby += 1}
            }
                }
                }

**The root with scroll event detector**

import SwiftUI
import Combine

@main
struct tempApp: App {
   
    @State var subs = Set<AnyCancellable>()
    @SceneBuilder
    
    var body: some Scene {
        WindowGroup {
            ContentView()
                .onAppear { trackScrollWheel() }
        }
    }
}

extension tempApp {
    func trackScrollWheel() {
        NSApp.publisher(for: \.currentEvent)
            .filter { event in event?.type == .scrollWheel }
            .throttle(for: .milliseconds(200),
                      scheduler: DispatchQueue.main,
                      latest: true)
            .sink {
                if let event = $0 {
                    if event.deltaX > 0 { print("right") }
                    if event.deltaX < 0 { print("left") }
                    if event.deltaY > 0 { print("down") }
                    if event.deltaY < 0 { print("up") }
                }
            }
            .store(in: &subs)
    }
}

mac os