When using a @StateObjects in my root view (ContentView) with multiple @Published vars I wanted to understand how the redrawing of views can be limited to the absolute minimum. Sometimes views are redrawn (due to a "@self changed" signal - see below) which should no need to be redrawn...

So here's a simple class with two properties

class UserProgress: ObservableObject {
    @Published var score : Int = 0 
    @Published var anotherScore : Int = 0
}

Each one should be rendered/used in separate Views

struct VarScoreView: View {
    var score: Int
    var body: some View {
        Self._printChanges()
        return VStack {
            Text("score (Var): \(self.score)")
        }
    }
}

struct VarAnotherScoreView: View {
    var anotherScore: Int
    var body: some View {
        Self._printChanges()
        return VStack {
            Text("an. score (Var): \(self.anotherScore)")
        }
    }
}

Additionally I have a button View which helps me to update the Observable Object:

struct ButtonView: View {
    @ObservedObject var progress: UserProgress

    var body: some View {
            VStack {
            Button("Increase Score") {
                progress.score += 1
            }
            Button("Increase another Score") {
                progress.anotherScore += 1
            }
        }
    }
}

Putting it all together

struct ContentView: View {

    @StateObject var up = UserProgress()

    var body: some View {
        print("------ changes detected in view -----")
        Self._printChanges()
        return VStack {
            ButtonView(progress: up)
            Spacer()
            VarScoreView(score: up.score)
            VarAnotherScoreView(anotherScore: up.anotherScore)
        }
    }
}

This produces the expected results visually and in the console 1) When clicking on the "Increas Score" Button:

------ changes detected in view -----
ContentView: _up changed.
VarScoreView: @self changed.

2) When clicking on the "Increase another Score" Buttong:

------ changes detected in view -----
ContentView: _up changed.
VarAnotherScoreView: @self changed.

But when I delete the Spacer() the VarScoreView also gets triggered for button "Increase another Score":

------ changes detected in view -----
ContentView: _up changed.
VarScoreView: @self changed.
VarAnotherScoreView: @self changed.

So the update of the VarScoreView seems to be triggered even though "up.score" is not updated just because of a layout issue?

How can I get deeper Insights into the inner Workings of "ContentView" to undersand the difference between the ContentView with and without the Spacer() (or other additional views)?