SKNode frame incorrect?

Question

This is the constructor for my NumberTile class:

class NumberTile: SKShapeNode {
    
    var tileColorArray = NSArray(objects: "#996666","#a65959","#b34d4d","#bf4040","#cc3333","#d92626","#e61919") //red
    
    init(xPos: NSInteger, yPos: NSInteger) {
        
        super.init()
        let size = CGSize(width: 40, height: 40)
        self.path = CGPathCreateWithRect(CGRect(origin: CGPointZero, size:size), nil)
        
        self.position = CGPointMake(0, (CGFloat)(yPos))
        let fillColor = UIColor(rgba: tileColorArray.objectAtIndex(Int(arc4random_uniform(UInt32(self.tileColorArray.count)))) as! String)
        
        self.fillColor = fillColor
        self.strokeColor = UIColor.blackColor()
        self.physicsBody = SKPhysicsBody(rectangleOfSize: self.frame.size, center: CGPointMake((CGFloat)(GlobalConstants.k_TILE_SIZE/2),(CGFloat)(GlobalConstants.k_TILE_SIZE/2)))
        
        self.physicsBody?.mass = GlobalConstants.k_TILE_MASS
        self.physicsBody?.friction = 1.0
        self.physicsBody?.allowsRotation = false
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

I have hard-coded the size to be 40 x 40 and the x-position to be 0.

I add NumberTiles to the scene with the following code:

let tile = NumberTile(xPos: xPos, yPos: yPos)
print("tile position: \(NSStringFromCGRect(tile.frame)) xPos:\(xPos)")
print("physic body: \(tile.physicsBody)")
addChild(tile)

xPos can be ignored as I hardcoded it in the constructor for debugging.

The result is:

tile position: {{-0.5, 373.5}, {41, 41}} xPos:0
physic body: Optional(<SKPhysicsBody> type:<Rectangle> representedObject:[<SKShapeNode> name:'(null)' accumulatedFrame:{{-0.5, 373.5}, {41, 41}}])

Why has the xPos been shifted by -0.5 and the width and height have been increased by 1?

Update

For the xPos, I have finally figured it out. In the constructor, I should set the origin to (0.5, 0.5) as follows:

self.path = CGPathCreateWithRect(CGRect(origin: CGPointMake(0.5, 0.5), size: size), nil)

But I still have no idea why the width and height are being increased by 1.

Answer 1

I believe that stroking the path will will increase the shape by the size of the stroke (which I am guessing is 0.5 on each side) That is what is giving you the 0.5 offset and the +1 to the size. Either inset your rect by one to account for it or don't set a stroke color