Strange black corners when using draw(_ rect:) function - ios

Question

If I put the code for my UIBezierPath inside the draw(_ rect:) function I get these strange very thin black corners around the view and the tail. When dragging the view (e.g. within a presented view controller) these thin lines also start flickering. I assume it's a weird rendering bug. Does anyone know if there is a way to fix this?
class RenderingView: UIView {
lazy var backgroundView: UIView = {
let view = UIView()
view.layer.cornerRadius = 8
view.translatesAutoresizingMaskIntoConstraints = false
return view
}()
private lazy var shadowView: UIView = {
let view = UIView()
view.translatesAutoresizingMaskIntoConstraints = false
return view
}()
private lazy var textLabel: UILabel = {
let label = UILabel()
label.numberOfLines = 0
label.textAlignment = .center
label.translatesAutoresizingMaskIntoConstraints = false
label.text = "Rendering Bug"
return label
}()
override init(frame: CGRect) {
super.init(frame: frame)
setup()
}
required init?(coder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
private func setup() {
backgroundColor = .clear
backgroundView.backgroundColor = .yellow
layer.borderWidth = 0
setupLayout()
}
private func setupLayout() {
[shadowView, backgroundView, textLabel].forEach(addSubview)
backgroundView.leadingAnchor.constraint(equalTo: leadingAnchor).isActive = true
backgroundView.topAnchor.constraint(equalTo: topAnchor).isActive = true
backgroundView.trailingAnchor.constraint(equalTo: trailingAnchor).isActive = true
backgroundView.bottomAnchor.constraint(equalTo: bottomAnchor).isActive = true
shadowView.leadingAnchor.constraint(equalTo: backgroundView.leadingAnchor).isActive = true
shadowView.topAnchor.constraint(equalTo: backgroundView.topAnchor).isActive = true
shadowView.trailingAnchor.constraint(equalTo: backgroundView.trailingAnchor).isActive = true
shadowView.bottomAnchor.constraint(equalTo: backgroundView.bottomAnchor).isActive = true
textLabel.leadingAnchor.constraint(equalTo: backgroundView.leadingAnchor, constant: 10).isActive = true
textLabel.trailingAnchor.constraint(equalTo: backgroundView.trailingAnchor, constant: -10).isActive = true
textLabel.topAnchor.constraint(equalTo: backgroundView.topAnchor, constant: 10).isActive = true
textLabel.bottomAnchor.constraint(equalTo: backgroundView.bottomAnchor, constant: -10).isActive = true
}
override func draw(_ rect: CGRect) {
shapeBackground()
}
private func shapeBackground() {
let tailLayer = CAShapeLayer()
let bezierPath = UIBezierPath(roundedRect: CGRect(x: backgroundView.bounds.minX,
y: backgroundView.bounds.minY,
width: backgroundView.bounds.width,
height: backgroundView.bounds.height - 12),
cornerRadius: 8)
let shadowBezierPath = UIBezierPath(roundedRect: CGRect(x: backgroundView.bounds.minX + 5,
y: backgroundView.bounds.minY + 10,
width: backgroundView.bounds.width - 10,
height: backgroundView.bounds.height - 12 - 10),
cornerRadius: 8)
[bezierPath, shadowBezierPath].forEach {
$0.move(to: CGPoint(x: backgroundView.bounds.midX - 12, y: backgroundView.bounds.maxY - 12))
$0.addLine(to: CGPoint(x: backgroundView.bounds.midX, y: backgroundView.bounds.maxY))
$0.addLine(to: CGPoint(x: backgroundView.bounds.midX + 12, y: backgroundView.bounds.maxY - 12))
$0.fill()
$0.close()
}
tailLayer.path = bezierPath.cgPath
tailLayer.fillColor = UIColor.white.cgColor
shadowView.layer.shadowPath = shadowBezierPath.cgPath
shadowView.layer.cornerRadius = 8
backgroundView.layer.masksToBounds = true
backgroundView.layer.mask = tailLayer
}
}
EDIT:
Turns out I had to use addClip() on the bezier paths to get rid of these corners

Answer 1

Not sure if this is what you are aiming for, but it looks flawless when you move the shapeBackground() method out of draw(_ rect:) and do some slight modifications.
I modified some of your drawing routines inside shapeBackground(), and moved the function into layoutSubviews() to calculate position of the tail from the frame made by constraints. I also added some variables for tailWidth, & tailHeight.
Like so:
class RenderingView: UIView {
lazy var backgroundView: UIView = {
let view = UIView()
view.layer.cornerRadius = 8
view.translatesAutoresizingMaskIntoConstraints = false
return view
}()
private lazy var shadowView: UIView = {
let view = UIView()
view.translatesAutoresizingMaskIntoConstraints = false
return view
}()
private lazy var textLabel: UILabel = {
let label = UILabel()
label.numberOfLines = 0
label.textAlignment = .center
label.translatesAutoresizingMaskIntoConstraints = false
label.text = "No Rendering Bug"
return label
}()
override init(frame: CGRect) {
super.init(frame: frame)
setup()
}
required init?(coder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
private func setup() {
backgroundColor = .clear
backgroundView.backgroundColor = .systemTeal
//backgroundView.frame.size = CGSize(width: 100, height: 100)
layer.borderWidth = 0
setupLayout()
}
private func setupLayout() {
[shadowView, backgroundView, textLabel].forEach(addSubview)
backgroundView.leadingAnchor.constraint(equalTo: leadingAnchor).isActive = true
backgroundView.topAnchor.constraint(equalTo: topAnchor).isActive = true
backgroundView.trailingAnchor.constraint(equalTo: trailingAnchor).isActive = true
backgroundView.bottomAnchor.constraint(equalTo: bottomAnchor).isActive = true
shadowView.leadingAnchor.constraint(equalTo: backgroundView.leadingAnchor).isActive = true
shadowView.topAnchor.constraint(equalTo: backgroundView.topAnchor).isActive = true
shadowView.trailingAnchor.constraint(equalTo: backgroundView.trailingAnchor).isActive = true
shadowView.bottomAnchor.constraint(equalTo: backgroundView.bottomAnchor).isActive = true
textLabel.leadingAnchor.constraint(equalTo: backgroundView.leadingAnchor, constant: 10).isActive = true
textLabel.trailingAnchor.constraint(equalTo: backgroundView.trailingAnchor, constant: -10).isActive = true
textLabel.topAnchor.constraint(equalTo: backgroundView.topAnchor, constant: 10).isActive = true
textLabel.bottomAnchor.constraint(equalTo: backgroundView.bottomAnchor, constant: -10).isActive = true
}
override func didMoveToWindow() {
super.didMoveToWindow()
}
override func layoutSubviews() {
super.layoutSubviews()
shapeBackground(color: UIColor.systemTeal)
}
override func draw(_ rect: CGRect) {
super.draw(rect)
}
private func shapeBackground(color: UIColor) {
let tailLayer = CAShapeLayer()
tailLayer.name = "tailLayer"
let tailWidth: CGFloat = 16
let tailHeight: CGFloat = 10
let bezierPath = UIBezierPath()
let shadowBezierPath = UIBezierPath()
[bezierPath, shadowBezierPath].forEach {
$0.move(to: CGPoint(x: 0, y: 0))
$0.addLine(to: CGPoint(x: tailWidth / 2, y: tailHeight))
$0.addLine(to: CGPoint(x: tailWidth, y: 0))
$0.fill()
$0.close()
}
tailLayer.path = bezierPath.cgPath
tailLayer.fillColor = color.cgColor
shadowView.layer.shadowPath = shadowBezierPath.cgPath
shadowView.layer.cornerRadius = 8
print(backgroundView.bounds.width)
tailLayer.frame = CGRect(x: (backgroundView.bounds.width - tailWidth) / 2,
y: backgroundView.bounds.maxY,
width: tailWidth,
height: tailHeight)
backgroundView.layer.masksToBounds = false
backgroundView.layer.addSublayer(tailLayer)
}
}