MarqueeLabel Please be fully aware that these use Private APIs.

MarqueeLabel-Minimal.swift

let label = UILabel()
label.text = "Swift is a modern, intuitive programming language crafted for all Apple platforms."
label.setValue(true, forKey: "marqueeEnabled")
label.setValue(true, forKey: "marqueeRunning")
label.setValue(0, forKey: "marqueeRepeatCount")

MarqueeLabel.swift

//
//  MarqueeLabel.swift
//  PrivateAPISample
//  
//  Created by Chronos2500 on 2025/05/13.
//

import SwiftUI

fileprivate let text = """
Swift is a modern, intuitive programming language crafted for all Apple platforms. 
"""

struct MarqueeLabelView: View {
    var body: some View {
        MarqueeLabel(
            text,
            font: .preferredFont(forTextStyle: .title1)
        )
    }
}

struct MarqueeLabel: UIViewRepresentable {
    var text: String
    var repeatCount: Int
    var font: UIFont
    var textColor: UIColor

    init(
        _ text: String,
        repeatCount: Int = 0,
        font: UIFont = .preferredFont(forTextStyle: .body),
        textColor: UIColor = .label
    ) {
        self.text = text
        self.repeatCount = repeatCount
        self.font = font
        self.textColor = textColor
    }

    func makeUIView(context: Context) -> UILabel {
        let label = UILabel()
        label.text = text
        label.textAlignment = .natural
        label.font = font
        label.textColor = textColor
        label.backgroundColor = .clear
        label.numberOfLines = 1
        label.setContentCompressionResistancePriority(.defaultLow, for: .horizontal)
        label.setContentHuggingPriority(.defaultLow, for: .horizontal)
        label.setContentHuggingPriority(.required, for: .vertical)
        label.setContentCompressionResistancePriority(.required, for: .vertical)
        label.adjustsFontForContentSizeCategory = true
        label.setValue(true, forKey: "marqueeEnabled")
        label.setValue(true, forKey: "marqueeRunning")
        label.setValue(repeatCount, forKey: "marqueeRepeatCount")
        label.setValue(40, forKey: "marqueeLoopPadding")
        label.setValue(true, forKey: "marqueeUpdatable")
        return label
    }
    func updateUIView(_ uiView: UILabel, context: Context) {
    }
}

#Preview {
    MarqueeLabelView()
}

@llsc12 I'm just looking at the internal impl. Apple has an internal _UILabelMarqueeAnimationDelegate object which listens to animation start and end. So you would set [self setValue:@1 forKey:@"marqueeRepeatCount"]; in all your labels, listen to animationDidStop:finished: in the delegate object of the longest running label, and notify other labels to start animation again.

The animation object contains the animation length, but not sure yet how UILabel calculates it. It's a relatively simple calc, but params such as rate are not exposed. Once I have all this implemented, I will post a small framework with an easy public API for what you need.

Very interesting, also thank you for your insights!

You can play around with what I came up with here:

https://github.com/LeoNatan/LNSystemMarqueeLabel