updateLayer not called on layer backed NSView

Question

Created Jun ’15

Replies 4

Boosts 0

Views 2.1k

Participants 5

I have the following `NSView` subclass, which is layer backed, and draws a `CAGradientLayer`. When I call `needsDisplay = true`, I'd expect `updateLayer` to be called, but it isn't. Is my understanding of what should happen incorrect, or have I done something wrong?

Thanks,

Luke

class ViewSubclass: NSView
{
     override var wantsUpdateLayer: Bool
     {
          return true
     }

     init()
     {
          super.init(frame: CGRectZero)

          self.wantsLayer = true
          self.layerContentsRedrawPolicy = NSViewLayerContentsRedrawPolicy.OnSetNeedsDisplay
     }

     required init?(coder: NSCoder)
     {
          fatalError("init(coder:) has not been implemented")
     }

     override func makeBackingLayer() -> CALayer
     {
          let saturationGradientLayer = CAGradientLayer()
          saturationGradientLayer.colors = [NSColor.whiteColor().CGColor,
               NSColor.redColor().CGColor]
          saturationGradientLayer.locations = [0.0, 1.0]
          saturationGradientLayer.startPoint = CGPoint(x: 0.0, y: 0.0)
          saturationGradientLayer.endPoint = CGPoint(x: 1.0, y: 0.0)

          return saturationGradientLayer
     }

     override func updateLayer()
     {
          NSLog("Update layer called")
     }

Boost

Answer 1

sstevenson OP

Jun ’15

How are you instantiating the view? In code or a xib file?

0

Answer 2

Michael Coding Monkey OP

Jun ’15

Update layer will only be called if you use ther apple internal backing layer and not overriding makeBackingLayer(), else NSView behaves layer hosted not backed.

0

Answer 3

AdrianS OP

Jun ’15

Did you:

1) Override wantsUpdateLayer to return true?

    override var wantsUpdateLayer: Bool {
        get{
                 return true
            }
    }

2) Set the layerContentsRedrawPolicy?

self.layerContentsRedrawPolicy = NSViewLayerContentsRedrawPolicy.OnSetNeedsDisplay;

No 2 above isn't necessary, but I use it as a force of habit. Either way, No 1 above will call updateLayer when "needsDisplay" is set to true

0

Answer 4

krzyzanowskim OP

Jul ’20

I wanted to update it (after 5 years) that NSView.updateLayer() is still not called despite all the magic:

Code Block swiftoverride var wantsUpdateLayer: Bool { true }
wantsLayer = true
layerContentsRedrawPolicy = .onSetNeedsDisplay

Code Block override func makeBackingLayer() -> CALayer {
		CATextLayer()
}

without custom makeBackingLayer, updateLayer() is called.

0