didDisplayNodeContentWithRenderingContext doesn't get called anymore on 2.8.1 vs 2.8

[christianselig]

Texture version: 2.8.1

I updated from Texture 2.8 to 2.8.1 and didDisplayNodeContentWithRenderingContext isn't getting called anymore. I use that block in the init of a layerBacked ASTextNode to get some custom drawing elements (highlighted elements basically).

I didn't have much time to investigate (iOS 13 time crunch) so I ended up just downgrading back to 2.8 where it works as expected, apologies for not much more information on the issue.

Searching in the Slack for it I see one person had encountered it too:

Does anyone know why didDisplayNodeContentWithRenderingContext block isn't called on ios 13? It gets called on ios 12 (edited)

(I don't believe it's an iOS 13 issue though, it works as expected on iOS 13 if you're using the 2.8 release.)

(Also thanks for all the awesome work the Texture team/contributors have been doing, 2.8.1 packed a ton of awesomeness especially around Dark Mode things, my hats are off to you and I greatly appreciate it!)

[choiks14]

same here

[christianselig]

Here's some super simple sample code showing it not working from a new project.

Code from Texture 2.8 where didDisplayNodeContentWithRenderingContext does get called:

class RootViewController: ASViewController<ASDisplayNode> {
    let rootNode = ASDisplayNode()
    let bodyNode = ASTextNode()

    init() {
        super.init(node: rootNode)

        bodyNode.attributedText = NSAttributedString(string: "Hello, world!", attributes: [.font: UIFont.systemFont(ofSize: 21.0, weight: .semibold), .foregroundColor: UIColor.black])
        rootNode.addSubnode(bodyNode)

        bodyNode.didDisplayNodeContentWithRenderingContext = { (context, drawParameters) in
            print("Is this ever called?") // Texture 3.0 never calls this. Texture 2.8 does.
        }

        rootNode.layoutSpecBlock = { (node, constrainedSize) in
            return ASCenterLayoutSpec(centeringOptions: .XY, sizingOptions: .minimumXY, child: self.bodyNode)
        }
    }

    required init?(coder aDecoder: NSCoder) { fatalError("\(#file) does not implement coder.") }
}

However if you change Cocoapods to point to the most recent commit of Texture (3.0) (and change the code sample to subclass ASDKViewController and change init() to override init()), you'll see didDisplayNodeContentWithRenderingContext will no longer get called.

This changes if you change from ASTextNode to ASTextNode2 (didDisplayNodeContentWithRenderingContext will get called) however ASTextNode2 is still missing a lot of helpful methods from ASTextNode like rectsForTextRange which prevents me from migrating over to it fully (in fact in my real project I use didDisplayNodeContentWithRenderingContext and rectsForTextRange together so it's even more important, haha).

[christianselig]

Ready for some Rube Goldberg magic? Issue seems to be that at some point between 2.8 and 3.0:

• ASTextNode (not ASTextNode2) added the displayWithParameters:isCancelled: method (you can see here)
• Which causes flags.implementsImageDisplay to be YES.
• This in turn causes shouldCreateGraphicsContext in ASDisplayNode+AsyncDisplay to be set to NO.
• Which in turns causes the graphics context to never be created, so it's nil.
• Slightly further down in the method that implements the block callback it's required that the graphics context be non-nil in order to call the callback. Since it's nil it just skips right past it and the block never gets called.

Note that ASTextNode2 on the other hand does not implement displayWithParameters:isCancelled:, so flags.implementsImageDisplay is NO which causes everything to be set up properly.

I'm admittedly not sure what the obvious fix is here or why ASTextNode implements that method while ASTextNode2 does not. For now I just reverted the ASTextNode.mm file to the 2.8 version and all works again on my end.

[garrettmoon]

@christianselig thank you for the thorough investigation!