How do you display a tooltip / hint on hover?

Question

How to display tooltip / hint on some view? As example, on the button.

Answer 1

Thanks to both Andrew and Sorin for the solution direction. The presented solutions mostly worked but when I used them they totally messed up the layout. It turns out that the Tooltip has its own size, frame etc. which isn't automatically matching the content.

In theory I could address those problems by using fixed frames etc. but that did not seem the right direction to me.

I have come up with the following (slightly more complex) but easy to use solution which doesn't have these drawbacks.

extension View {
    func tooltip(_ tip: String) -> some View {
        background(GeometryReader { childGeometry in
            TooltipView(tip, geometry: childGeometry) {
                self
            }
        })
    }
}

private struct TooltipView<Content>: View where Content: View {
    let content: () -> Content
    let tip: String
    let geometry: GeometryProxy

    init(_ tip: String, geometry: GeometryProxy, @ViewBuilder content: @escaping () -> Content) {
        self.content = content
        self.tip = tip
        self.geometry = geometry
    }

    var body: some View {
        Tooltip(tip, content: content)
            .frame(width: geometry.size.width, height: geometry.size.height)
    }
}

private struct Tooltip<Content: View>: NSViewRepresentable {
    typealias NSViewType = NSHostingView<Content>

    init(_ text: String?, @ViewBuilder content: () -> Content) {
        self.text = text
        self.content = content()
    }

    let text: String?
    let content: Content

    func makeNSView(context _: Context) -> NSHostingView<Content> {
        NSViewType(rootView: content)
    }

    func updateNSView(_ nsView: NSHostingView<Content>, context _: Context) {
        nsView.rootView = content
        nsView.toolTip = text
    }
}

I have added a GeometryReader to the content of the tooltip and then constrain the size of the Tooltip to the match the size of the content.

To use it:

Toggle("...", isOn: $isOn)
   .tooltip("This is my tip")

Addition January 2023

The latest release of SwiftUI requires a small change in the tooltip method. I noticed rapid redrawing problems. By adding a ZStack this problem is addressed:

extension View {
    func tooltip(_ tip: String) -> some View {
        ZStack {
            background(GeometryReader { childGeometry in
                TooltipView(tip, geometry: childGeometry) {
                    self
                }
            })
            // self
        }
    }
}

Feb 2023: I removed the second self. With the extra self there is a glow on the parent.