HitTest with CAShapeLayer doesn't work - ios

Question

I use the following code to check wether a point of a player is in a circle area:
if ([circle.presentationLayer hitTest:player.position])
{
NSLog(#"hit");
}
My circle is a CAShapeLayer:
CAShapeLayer *circle = [CAShapeLayer layer];
CGFloat radius = 50;
[circle setMasksToBounds:YES];
[circle setBackgroundColor:[UIColor redColor].CGColor];
[circle setCornerRadius:radius1];
[circle setBounds:CGRectMake(0.0f, 0.0f, radius *2, radius *2)];
[self.view.layer addSublayer:circle];
The collision detection works very well that way.
Now I don't want to hittest the player's position with a circle layer but with a CAShapeLayer drawn along a custom path:
CAShapeLayer *customLayer = [CAShapeLayer layer];
customLayer.path = customPath.CGPath;
customLayer.fillColor = [UIColor yellowColor].CGColor;
customLayer.shouldRasterize = YES;
customLayer.opacity = 0.2;
[self.view.layer addSublayer: customLayer];
When I want to hittest the player's position with the custom layer the hittest doesn't work anymore.
How can I solve this problem?

Answer 1

Are you converting the position to the correct relative position?
For example:
CGPoint layerPoint = [[dynamicView layer] convertPoint:touchLocation toLayer:sublayer];
Also, perhaps you need CGPathContainsPoint:
if(CGPathContainsPoint(shapeLayer.path, 0, layerPoint, YES))
{

Answer 2

You are assigning the bounds/frame of your circle, but not that of your bezier path. I did not know that until I stumbled onto it myself, but when you create a shape and assign a path to a CAShapeLayer(), you must assign the CALayer's frame (or separately the position and the bounds) because the frame of a CALayer(), as per Apple's documentation, defaults to a CGZeroRect and does not get automatically updated when you set the path. hitTest() is based on the position+bounds (or frame) and therefore fails. The documentation says:
/* Returns the farthest descendant of the layer containing point 'p'.
* Siblings are searched in top-to-bottom order. 'p' is defined to be
* in the coordinate space of the receiver's nearest ancestor that
* isn't a CATransformLayer (transform layers don't have a 2D
* coordinate space in which the point could be specified). */
(nullable CALayer *)hitTest:(CGPoint)p;
/* Returns true if the bounds of the layer contains point 'p'. */
(BOOL)containsPoint:(CGPoint)p;
A quick unit test shows this (extension CGPath is useful and included after):
func testShapeLayer() {
let layer = CAShapeLayer()
let bezier = NSBezierPath(rect: NSMakeRect(0,0,10,10))
layer.path = bezier.CGPath
// remove the following line to FAIL the test
layer.frame = NSMakeRect(0,0,10,10)
XCTAssertNotNil(layer.hitTest(CGPoint(x:5,y:5)))
XCTAssertTrue(layer.contains(CGPoint(x:5,y:5)))
}
extension NSBezierPath {
public var CGPath: CGPath {
let path = CGMutablePath()
var points = [CGPoint](repeating: .zero, count: 3)
for i in 0 ..< self.elementCount {
let type = self.element(at: i, associatedPoints: &points)
switch type {
case .moveToBezierPathElement: path.move(to: CGPoint(x: points[0].x, y: points[0].y) )
case .lineToBezierPathElement: path.addLine(to: CGPoint(x: points[0].x, y: points[0].y) )
case .curveToBezierPathElement: path.addCurve( to: CGPoint(x: points[2].x, y: points[2].y),
control1: CGPoint(x: points[0].x, y: points[0].y),
control2: CGPoint(x: points[1].x, y: points[1].y) )
case .closePathBezierPathElement: path.closeSubpath()
}
}
return path
}
}
Yet, that's probably not what you want: you want the path to be used for hitTesting(), not just the frame. I would therefore probably add an extension to your hitTesting routine: if the CAShapeLayer() is hit, it means that it is within the frame, then you can be more specific and check with CGPathContainsPoint() like the other answer mentioned.