Example of how to create a Text that shrinks font size when compressed vertically. (Workaround for limitation in SwiftUI)

SingeLineVerticalCompressedLabel.swift

import SwiftUI


// Workaround for a limitation in SwiftUI's Text view that prevents it
// from shrinking the font size when using `lineLimit`

struct ContentView: View {
    let text:String
    let bottomRectHeight:CGFloat
    
    var body: some View {
        VStack(alignment:.center, spacing:0 ) {
            // Use GeometryReader to scale the font size based on height
            // of the container
            GeometryReader {reader in
                Text(self.text)
                    .font(Font.system(size: 60.0 * reader.size.height / 80))
                    .minimumScaleFactor(0.15)
                    .lineLimit(1)
                    .background(Color.blue)
            }
            
            Rectangle()
                .strokeBorder()
                .foregroundColor(Color.purple)
                .frame(maxWidth: .infinity)
                .frame(height:self.bottomRectHeight)
        }
        .frame(width: 100, height: 100)
        .background(Color.green)
    }
}

struct ContentPreviewWrapper : View {
    @State var height:CGFloat = 40.0

    var body: some View {
        VStack(spacing:20) {
            ContentView(text:"Hello world", bottomRectHeight:self.height)

            ContentView(text:"150", bottomRectHeight:self.height)
            
            Slider(value:$height, in:0.0...100.0)
                .padding()
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    
    static var previews: some View {
        ContentPreviewWrapper()
    }
}