Testing .contentSize in UIScrollView

ContentSizeViewController.swift

//
//  Created by Don Mag on 3/4/23.
//

import UIKit

class ContentSizeViewController: UIViewController, UIScrollViewDelegate {

	let scrollView = UIScrollView()
	
	let infoLabelA = UILabel()
	let infoLabelB = UILabel()
	let infoLabelC = UILabel()

	var infoCount: Int = 0
	
	let w: CGFloat = 800.0
	let h: CGFloat = 1000.0

	var fullSize: Bool = true {
		didSet {
			let newW = fullSize ? w : w * 0.5
			let newH = fullSize ? h : h * 0.5
			let newSZ = CGSize(width: newW, height: newH)
			scrollView.contentSize = newSZ
			infoLabelB.text = ".contentSize set to: \(newSZ)"
			// so infoLabelA gets updated
			updateInfo()
			// so infoLabelC gets updated
			scrollViewDidScroll(scrollView)
		}
	}
	
	override func viewDidLoad() {
		super.viewDidLoad()
		
		view.backgroundColor = UIColor(white: 0.95, alpha: 1.0)
		
		let g = view.safeAreaLayoutGuide
		
		var config = UIButton.Configuration.filled()
		config.buttonSize = .medium
		config.cornerStyle = .medium
		config.title = "Get .contentSize"
		
		let btnA = UIButton(configuration: config)
		btnA.addAction (
			UIAction { _ in
				self.updateInfo()
			}, for: .touchUpInside
		)
		
		infoLabelA.backgroundColor = .cyan
		infoLabelA.textAlignment = .center
		infoLabelA.font = .systemFont(ofSize: 14, weight: .regular)
		
		config.title = "Toggle .contentSize"
		
		let btnB = UIButton(configuration: config)
		btnB.addAction (
			UIAction { _ in
				self.fullSize.toggle()
			}, for: .touchUpInside
		)
		
		infoLabelB.backgroundColor = .cyan
		infoLabelB.textAlignment = .center
		infoLabelB.font = .systemFont(ofSize: 14, weight: .regular)
		
		// so we can see the scrollView frame
		scrollView.backgroundColor = .systemRed
		scrollView.layer.borderColor = UIColor.black.cgColor
		scrollView.layer.borderWidth = 1

		infoLabelC.backgroundColor = .cyan
		infoLabelC.textAlignment = .center
		infoLabelC.numberOfLines = 0
		infoLabelC.font = .systemFont(ofSize: 14, weight: .regular)
		
		[btnA, infoLabelA, btnB, infoLabelB, scrollView, infoLabelC].forEach { v in
			v.translatesAutoresizingMaskIntoConstraints = false
			view.addSubview(v)
		}
		
		NSLayoutConstraint.activate([

			btnA.topAnchor.constraint(equalTo: g.topAnchor, constant: 8.0),
			btnA.leadingAnchor.constraint(equalTo: g.leadingAnchor, constant: 40.0),
			btnA.trailingAnchor.constraint(equalTo: g.trailingAnchor, constant: -40.0),
			infoLabelA.topAnchor.constraint(equalTo: btnA.bottomAnchor, constant: 8.0),
			infoLabelA.leadingAnchor.constraint(equalTo: g.leadingAnchor, constant: 40.0),
			infoLabelA.trailingAnchor.constraint(equalTo: g.trailingAnchor, constant: -40.0),
			infoLabelA.heightAnchor.constraint(equalToConstant: 30.0),

			btnB.topAnchor.constraint(equalTo: infoLabelA.bottomAnchor, constant: 8.0),
			btnB.leadingAnchor.constraint(equalTo: g.leadingAnchor, constant: 40.0),
			btnB.trailingAnchor.constraint(equalTo: g.trailingAnchor, constant: -40.0),
			infoLabelB.topAnchor.constraint(equalTo: btnB.bottomAnchor, constant: 8.0),
			infoLabelB.leadingAnchor.constraint(equalTo: g.leadingAnchor, constant: 40.0),
			infoLabelB.trailingAnchor.constraint(equalTo: g.trailingAnchor, constant: -40.0),
			infoLabelB.heightAnchor.constraint(equalToConstant: 30.0),

			scrollView.topAnchor.constraint(equalTo: infoLabelB.bottomAnchor, constant: 20.0),
			scrollView.leadingAnchor.constraint(equalTo: g.leadingAnchor, constant: 60.0),
			scrollView.trailingAnchor.constraint(equalTo: g.trailingAnchor, constant: -60.0),
			scrollView.bottomAnchor.constraint(equalTo: infoLabelC.topAnchor, constant: -20.0),
			
			infoLabelC.leadingAnchor.constraint(equalTo: g.leadingAnchor, constant: 40.0),
			infoLabelC.trailingAnchor.constraint(equalTo: g.trailingAnchor, constant: -40.0),
			infoLabelC.heightAnchor.constraint(equalToConstant: 50.0),
			infoLabelC.bottomAnchor.constraint(equalTo: g.bottomAnchor, constant: -8.0),
			
		])
		
		let names: [String] = [
			"Top-Left",
			"Top-Right",
			"Bottom-Left",
			"Bottom-Right",
			"Center",
		]
		let colors: [UIColor] = [
			.init(red: 1.0, green: 0.8, blue: 0.8, alpha: 1.0),
			.init(red: 0.8, green: 1.0, blue: 0.8, alpha: 1.0),
			.init(red: 0.8, green: 0.8, blue: 1.0, alpha: 1.0),
			.init(red: 0.8, green: 1.0, blue: 1.0, alpha: 1.0),
			.init(red: 1.0, green: 1.0, blue: 0.8, alpha: 1.0).withAlphaComponent(0.5),
		]
		
		var labels: [UILabel] = []
		
		for (str, c) in zip(names, colors) {
			let v = UILabel()
			v.textAlignment = .center
			v.font = .systemFont(ofSize: 40, weight: .light)
			v.text = str
			v.backgroundColor = c
			v.frame = CGRect(x: 0, y: 0, width: w * 0.5, height: h * 0.5)
			labels.append(v)
			scrollView.addSubview(v)
		}
		
		labels[0].center = .init(x: w * 0.25, y: h * 0.25)
		labels[1].center = .init(x: w * 0.75, y: h * 0.25)
		labels[2].center = .init(x: w * 0.25, y: h * 0.75)
		labels[3].center = .init(x: w * 0.75, y: h * 0.75)
		labels[4].center = .init(x: w * 0.5, y: h * 0.5)

		scrollView.delegate = self
		
		fullSize = true
	}
	
	func updateInfo() {
		infoCount += 1
		infoLabelA.text = "\(infoCount) :: .contentSize = \(scrollView.contentSize)"
	}
	
	func scrollViewDidScroll(_ scrollView: UIScrollView) {
		let pt = String(format: ".contentOffset: (%0.2f, %0.2f)", scrollView.contentOffset.x, scrollView.contentOffset.y)
		let sz = String(format: ".contentSize: (%0.2f, %0.2f)", scrollView.contentSize.width, scrollView.contentSize.height)
		infoLabelC.text = "\(pt)\n\(sz)"
	}
	
}