Some visual bug with CALayer - ios

Question

I have a UITableView with the following cells layout:
• UIView
•• UIImageView
••• Semi-transparent overlay UIView as subview of UIImageView
There are also icon view imitating the "play" button and UILabel, but they seem to be not related to this bug.
And I have the following code:
override func layoutSubviews() {
super.layoutSubviews()
createPath()
}
private func createPath() {
let padding = CGFloat(16)
let bottomLineLength = CGFloat(64)
let arcPadding = CGFloat(8)
let width = self.contentView.frame.width
let height = self.contentView.frame.height
if pathLayer != nil {
pathLayer?.removeFromSuperlayer()
}
pathLayer = CAShapeLayer()
let path = UIBezierPath()
path.move(to: CGPoint(x: padding + arcPadding, y: padding))
path.addLine(to: CGPoint(x: width - padding - arcPadding, y: padding))
// Top-Right arc
path.addArc(withCenter: CGPoint(x: width - padding - arcPadding, y: padding + arcPadding),
radius: arcPadding,
startAngle: CGFloat(3 * M_PI / 2),
endAngle: CGFloat(M_PI * 2),
clockwise: true)
path.move(to: CGPoint(x: width - padding, y: padding + arcPadding))
path.addLine(to: CGPoint(x: width - padding, y: height - padding - arcPadding))
// Bottom-Right arc
path.addArc(withCenter: CGPoint(x: width - padding - arcPadding, y: height - padding - arcPadding),
radius: arcPadding,
startAngle: CGFloat(M_PI * 2),
endAngle: CGFloat(M_PI / 2),
clockwise: true)
path.move(to: CGPoint(x: width - padding - arcPadding, y: height - padding))
path.addLine(to: CGPoint(x: width - padding - bottomLineLength, y: height - padding))
path.move(to: CGPoint(x: padding + bottomLineLength, y: height - padding))
path.addLine(to: CGPoint(x: padding + arcPadding, y: height - padding))
// Bottom-Left arc
path.addArc(withCenter: CGPoint(x: padding + arcPadding, y: height - padding - arcPadding),
radius: arcPadding,
startAngle: CGFloat(M_PI / 2),
endAngle: CGFloat(M_PI),
clockwise: true)
path.move(to: CGPoint(x: padding, y: height - padding - arcPadding))
path.addLine(to: CGPoint(x: padding, y: padding + arcPadding))
// Top-Left arc
path.addArc(withCenter: CGPoint(x: padding + arcPadding, y: padding + arcPadding),
radius: arcPadding,
startAngle: CGFloat(M_PI),
endAngle: CGFloat(3 * M_PI / 2),
clockwise: true)
pathLayer?.rasterizationScale = 2 * UIScreen.main.scale
pathLayer?.shouldRasterize = true
pathLayer?.strokeColor = UIColor(red: 0xFF/255, green: 0xFF/255, blue: 0xFF/255, alpha: 0.5).cgColor
pathLayer?.lineWidth = 2.0
pathLayer?.path = path.cgPath
contentView.layer.addSublayer(pathLayer!)
}
I'm calling it in layoutSubviews for re-creating the path on device rotation.
And if you look at the screenshot, there are some black and rotated a bit black "holes" near the path. All of them look the same, and they are surely not present on the image in UIImageView.
I think it's related to my CALayer. How to fix it?

Answer 1

Your problem is these black wedges:
The underlying cause is that the default fillColor of a CAShapeLayer is opaque black. Set it to nil to avoid filling:
pathLayer?.fillColor = nil
That done, let me show you a shorter way to construct your path:
let cgPath = CGMutablePath()
let start = CGPoint(x: padding + bottomLineLength, y: height - padding)
let blCorner = CGPoint(x: padding, y: height - padding)
let tlCorner = CGPoint(x: padding, y: padding)
let trCorner = CGPoint(x: width - padding, y: padding)
let brCorner = CGPoint(x: width - padding, y: height - padding)
let end = CGPoint(x: width - padding - bottomLineLength, y: height - padding)
cgPath.move(to: start)
cgPath.addArc(tangent1End: blCorner, tangent2End: tlCorner, radius: arcPadding)
cgPath.addArc(tangent1End: tlCorner, tangent2End: trCorner, radius: arcPadding)
cgPath.addArc(tangent1End: trCorner, tangent2End: brCorner, radius: arcPadding)
cgPath.addArc(tangent1End: brCorner, tangent2End: end, radius: arcPadding)
cgPath.addLine(to: end)
shapeLayer.path = cgPath
Result: