Accessibility Border Button

BorderButton.swift

import UIKit

class BorderButton: UIButton {
  
  private class BorderLayer: CAShapeLayer {
    fileprivate var _borderWidth: CGFloat { UIAccessibility.isBoldTextEnabled ? 2.0 : 1.0 }
    fileprivate var _cornerRadius: CGFloat = 4.0
    
    override var lineWidth: CGFloat { get { _borderWidth } set { } }
    override var fillColor: CGColor? { get { UIColor.clear.cgColor } set { } }

    override var path: CGPath? { get { super.path } set { }  }
    
    fileprivate func updateBorder() {
      let rect = CGRect(origin: .zero, size: self.frame.size).insetBy(dx: _borderWidth, dy: _borderWidth)
      super.path = UIBezierPath(roundedRect: rect, cornerRadius: _cornerRadius).cgPath
    }
  }
  
  override class var layerClass: AnyClass { BorderLayer.self }
  private var borderLayer: BorderLayer? { self.layer as? BorderLayer }
  
  // This is called regardless of how the AXButton is created, IB or code
  override func didMoveToSuperview() {
    super.didMoveToSuperview()
    self.titleLabel?.adjustsFontForContentSizeCategory = true
    self.titleLabel?.font = UIFont.preferredFont(forTextStyle: .body)
  }
  
  override func layoutSubviews() {
    super.layoutSubviews()
    
    // Disable CALayer's implicit animations while changing layer properties.
    CATransaction.setDisableActions(true)
    
    // Make its color match the view's tintColor.
    // Since we are inside `layoutSubviews()`, UIKit has already set `UITraitCollection.current`
    // to be the view's `traitCollection`. Calling `cgColor` will resolve the dynamic tint color,
    // using that trait collection, to a static `CGColor`.
    // When the traits change, UIKit ensures it calls `layoutSubviews` again.
    self.borderLayer?.strokeColor = self.tintColor.cgColor
    self.borderLayer?.updateBorder()
    
    CATransaction.setDisableActions(false)
  }
}