SlowLabelViewController.swift

//
//  SlowLabelViewController.swift
//
//  Created by Don Mag on 12/14/22.
//
//	Demonstrates how slow UILabel rendering when using High-Unicode strings

class SlowLabelViewController: UIViewController {
	
	var lowAsciiStr: String = ""
	var highUnicodeStr: String = ""
	
	var promptShowing: Bool = true

	let segControl = UISegmentedControl(items: ["Low ASCII", "High Unicode"])

	let theLabel = UILabel()
	
	override func viewDidLoad() {
		super.viewDidLoad()

		let toggleBtn = UIButton()
		let scrollView = UIScrollView()
		
		[segControl, toggleBtn, theLabel, scrollView].forEach { v in
			v.translatesAutoresizingMaskIntoConstraints = false
		}
		
		scrollView.addSubview(theLabel)
		view.addSubview(segControl)
		view.addSubview(toggleBtn)
		view.addSubview(scrollView)
		
		let g = view.safeAreaLayoutGuide
		let cg = scrollView.contentLayoutGuide
		let fg = scrollView.frameLayoutGuide
		
		NSLayoutConstraint.activate([
			
			segControl.topAnchor.constraint(equalTo: g.topAnchor, constant: 20.0),
			segControl.leadingAnchor.constraint(equalTo: g.leadingAnchor, constant: 20.0),
			segControl.trailingAnchor.constraint(equalTo: g.trailingAnchor, constant: -20.0),
			
			toggleBtn.topAnchor.constraint(equalTo: segControl.bottomAnchor, constant: 20.0),
			toggleBtn.leadingAnchor.constraint(equalTo: g.leadingAnchor, constant: 20.0),
			toggleBtn.trailingAnchor.constraint(equalTo: g.trailingAnchor, constant: -20.0),

			scrollView.topAnchor.constraint(equalTo: toggleBtn.bottomAnchor, constant: 20.0),
			scrollView.leadingAnchor.constraint(equalTo: g.leadingAnchor, constant: 20.0),
			scrollView.trailingAnchor.constraint(equalTo: g.trailingAnchor, constant: -20.0),
			scrollView.bottomAnchor.constraint(equalTo: g.bottomAnchor, constant: -20.0),

			theLabel.topAnchor.constraint(equalTo: cg.topAnchor, constant: 8.0),
			theLabel.leadingAnchor.constraint(equalTo: cg.leadingAnchor, constant: 8.0),
			theLabel.trailingAnchor.constraint(equalTo: cg.trailingAnchor, constant: -8.0),
			theLabel.bottomAnchor.constraint(equalTo: cg.bottomAnchor, constant: -8.0),
			
			theLabel.widthAnchor.constraint(equalTo: fg.widthAnchor, constant: -16.0),

		])
		
		toggleBtn.setTitle("Toggle the Text", for: [])
		toggleBtn.setTitleColor(.white, for: .normal)
		toggleBtn.setTitleColor(.lightGray, for: .highlighted)
		toggleBtn.backgroundColor = .systemGreen
		toggleBtn.layer.cornerRadius = 8.0
		
		scrollView.backgroundColor = .systemRed
		
		theLabel.backgroundColor = UIColor(white: 0.95, alpha: 1.0)
		theLabel.textAlignment = .center
		theLabel.numberOfLines = 0
		
		segControl.selectedSegmentIndex = 0
		
		toggleBtn.addTarget(self, action: #selector(toggleTapped(_:)), for: .touchUpInside)
		segControl.addTarget(self, action: #selector(segChanged(_:)), for: .valueChanged)

		// let's create some long strings to set as the label text
		var s: String = ""
		let n = 50
		
		s = ""
		for i in 1...n {
			s += "←↑→↓↔↕↖↗↘↙↺↻⇄⇅⇆⇇⇈⇉⇊⇋⇌⇍⇎⇏⇐⇑⇒⇓⇔⇕⇖⇗⇘⇙⇚⇛⇜⇝⇞⇟⇠⇡⇢⇣⇤⇥⇦⇧⇨⇩\nLine \(i) of \(n)\n\n"
		}
		highUnicodeStr = s
		
		s = ""
		for i in 1...50 {
			s += "The quick red fox jumps over the lazy brown dog before he eats breakfast.\n\(i) of \(n)\n\n"
		}
		lowAsciiStr = s

		promptShowing = false
		toggleTapped(nil)
	}
	
	@objc func toggleTapped(_ sender: Any?) {
		promptShowing.toggle()
		if promptShowing {
			if segControl.selectedSegmentIndex == 0 {
				theLabel.text = "\nThis is an example of \"Low ASCII\" text.\n\nThe quick red fox jumps over the lazy brown dog before he eats breakfast.\n\nWhen we set the .text property of a UILabel it will be very fast.\n\n"
			} else {
				theLabel.text = "\nThis is an example of \"High Unicode\" text.\n\n←↑→↓↔↕↖↗↘↙↺↻⇄⇅⇆⇇⇈⇉⇊⇋⇌⇍⇎⇏⇐⇑⇒⇓⇔⇕⇖⇗⇘⇙⇚⇛⇜⇝⇞⇟⇠⇡⇢⇣⇤⇥⇦⇧⇨⇩\n\nWhen we set the .text property of a UILabel it will be very slow.\n\n"
			}
		} else {
			if segControl.selectedSegmentIndex == 0 {
				theLabel.text = lowAsciiStr
			} else {
				theLabel.text = highUnicodeStr
			}
		}
	}
	
	@objc func segChanged(_ sender: Any?) {
		promptShowing = false
		toggleTapped(nil)
	}
	
}