CATiledLayer renders too few tiles on macOS

Question

Created Dec ’20

Replies 2

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Views 1.6k

Participants 2

CATiledLayer doesn't work as expected on macOS.
It's choosing to render too few tiles.

In my example, my view is 300px wide. I set layer's transform scale to 4x.
In that case, CATiledLayer renders only two tiles: 50px wide at 2x scale, and stretches them.

Interestingly, when I run similar code on iOS, it works correctly - it renders 3 tiles, 25px wide at 4x scale.

Is it a bug or am I missing something here?

My code below:

Code Block swiftclass WaveformView: NSView {
    var scale: CGFloat = 1.0 {
        didSet {
            layer?.transform = CATransform3DScale(CATransform3DIdentity, scale, 1.0, 1.0)
            layer?.setNeedsDisplay(bounds)
        }
    }
    private var tiledLayer: CATiledLayer { layer as! CATiledLayer }
    override init(frame frameRect: NSRect) {
        super.init(frame: frameRect)
        wantsLayer = true
        tiledLayer.levelsOfDetail = 8
        tiledLayer.levelsOfDetailBias = 8
        tiledLayer.tileSize = CGSize(width: 100.0, height: .infinity)
        tiledLayer.contentsScale = 1.0
    }
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    override func draw(_ dirtyRect: NSRect) {
        let nsContext = NSGraphicsContext.current!
        let cgContext = nsContext.cgContext
        cgContext.saveGState()
        let scaleX: CGFloat = cgContext.ctm.a
        NSColor.red.setStroke()
        NSBezierPath(rect: dirtyRect)
            .stroke()
        let fontSize: CGFloat = 12.0
        let attr = [
            NSAttributedString.Key.font: NSFont.systemFont(ofSize: fontSize)
          ]
        let str = "S: \(scaleX)\n\(dirtyRect.width)" as NSString
        str.draw(at: NSPoint(x: dirtyRect.minX, y: dirtyRect.midY), withAttributes: attr)
        nsContext.cgContext.restoreGState()
    }
    override func makeBackingLayer() -> CALayer {
        return CATiledLayer()
    }
}

Boost

Answer 1

smialek OP

Dec ’20

Ok, it appears that CATiledLayer behaves unexpectedly when it's scaled only in one axis. When I applied scale transform to both X and Y axis, tiles were rendered correctly.

Any chance that some Apple engineer could relate to this and confirm whether this is intended?

1

Answer 2

mike woodworth OP

Apr ’21

I just ran into this same issue... did you find a work around?

0