AutoLayout Hugging Priority and Compression Resistance Priority tests

playground.swift

import PlaygroundSupport
import UIKit

func makeLabels(left: String, right: String) -> (UIView, UILabel, UILabel) {
    let leftLb: UILabel = {
        let label = UILabel(frame: .zero)
        label.textAlignment = .left
        label.backgroundColor = .blue
        label.text = left
        return label
    }()
    
    let rightLb: UILabel = {
        let label = UILabel(frame: .zero)
        label.textAlignment = .right
        label.backgroundColor = .purple
        label.text = right
        return label
    }()
    
    let view = UIView(frame: .zero)
    
    for v: UILabel in [leftLb, rightLb] {
        v.translatesAutoresizingMaskIntoConstraints = false
        v.font = UIFont.systemFont(ofSize: 14, weight: UIFont.Weight.regular)
        v.numberOfLines = 0
        v.textColor = .white
        view.addSubview(v)
    }
    NSLayoutConstraint.activate([
        leftLb.leadingAnchor.constraint(equalTo: view.leadingAnchor),
        leftLb.topAnchor.constraint(equalTo: view.topAnchor),
        leftLb.bottomAnchor.constraint(equalTo: view.bottomAnchor),
        rightLb.leadingAnchor.constraint(equalTo: leftLb.trailingAnchor),
        rightLb.topAnchor.constraint(equalTo: view.topAnchor),
        rightLb.trailingAnchor.constraint(equalTo: view.trailingAnchor),
        rightLb.bottomAnchor.constraint(equalTo: view.bottomAnchor),
    ])
    return (view, leftLb, rightLb)
}

let frame = CGRect(x:0, y:0, width: 300, height: 250)
let contentView = UIView(frame: frame)
contentView.backgroundColor = .white
let stack = UIStackView(frame: frame)

stack.axis = .vertical
stack.distribution = .fillEqually
stack.alignment = .fill
stack.spacing = 2
stack.translatesAutoresizingMaskIntoConstraints = false

contentView.addSubview(stack)

NSLayoutConstraint.activate([
    stack.leadingAnchor.constraint(equalTo: contentView.leadingAnchor, constant: 5),
    stack.topAnchor.constraint(equalTo: contentView.topAnchor, constant: 5),
    stack.trailingAnchor.constraint(equalTo: contentView.trailingAnchor, constant: -5),
    stack.bottomAnchor.constraint(equalTo: contentView.bottomAnchor, constant: -5),
])

stack.addArrangedSubview({
    let (view,left,right) = makeLabels(left: "Hugging High", right: "Hugging High")
    left.setContentHuggingPriority(.defaultHigh, for: .horizontal)
    right.setContentHuggingPriority(.defaultHigh, for: .horizontal)
    return view
    }())

stack.addArrangedSubview({
    let (view,left,right) = makeLabels(left: "Hugging Low", right: "Hugging High")
    left.setContentHuggingPriority(.defaultLow, for: .horizontal)
    right.setContentHuggingPriority(.defaultHigh, for: .horizontal)
    return view
    }())

stack.addArrangedSubview({
    let (view,left,right) = makeLabels(left: "Compression High", right: "Compression High")
    left.setContentCompressionResistancePriority(.defaultHigh, for: .horizontal)
    right.setContentCompressionResistancePriority(.defaultHigh, for: .horizontal)
    return view
    }())

stack.addArrangedSubview({
    let (view,left,right) = makeLabels(left: "Compression High", right: "Compression Low")
    left.setContentCompressionResistancePriority(.defaultHigh, for: .horizontal)
    right.setContentCompressionResistancePriority(.defaultLow, for: .horizontal)
    return view
    }())
stack.addArrangedSubview({
    let (view,left,right) = makeLabels(left: "Hugging Low\nCompression High", right: "Hugging High\nCompression Low")
    left.setContentHuggingPriority(.defaultLow, for: .horizontal)
    right.setContentHuggingPriority(.defaultHigh, for: .horizontal)
    left.setContentCompressionResistancePriority(.defaultHigh, for: .horizontal)
    right.setContentCompressionResistancePriority(.defaultLow, for: .horizontal)
    return view
    }())
stack.addArrangedSubview({
    let (view,left,right) = makeLabels(left: "Hugging Low\nCompression Low", right: "Hugging High\nCompression Hight")
    left.setContentHuggingPriority(.defaultLow, for: .horizontal)
    right.setContentHuggingPriority(.defaultHigh, for: .horizontal)
    left.setContentCompressionResistancePriority(.defaultLow, for: .horizontal)
    right.setContentCompressionResistancePriority(.defaultHigh, for: .horizontal)
    return view
    }())
PlaygroundPage.current.liveView = contentView