Animate sizeToFit

Could you detail what you get and what you expect ?

AFAIU, animation works by layering an image "capture" over the view to animate and then apply the animation on this layer. Thus, I don't think it will change the font size, but scale the image. I don't think sizeToFit is appropriate here.

May have a look at using transform:

https://stackoverflow.com/questions/14494566/animating-uilabel-font-size-change

So I understand you want to animate (through NSAnimation), the change of the label's text in a MacOS app ?

And the change occurs only abruptly (probably after the 4 seconds) ?

It would help to see or reproduce exactly what you get. Could you post the complete code the the class ?

I want to animate (using any method) the change of the label's text in a macOS app. With the code I provide, the change occurs when I click the button. I see no animation and no delay.

import Cocoa
class ViewController: NSViewController {
    @IBOutlet weak var label1: NSTextField!

    override func viewDidLoad() {
        super.viewDidLoad()
    }

    @IBAction func button2(_ sender: NSButton) {
        NSAnimationContext.runAnimationGroup({ (context) in
            context.duration = 4.0
            label1.stringValue = "long, long text"
            label1.animator().sizeToFit()
        })
    }
}

What I understand from what you show:

• the change of text should be done in the completion handler of the animation
• but it will not be possible to animate the sizeToFit
• stated otherwise, the change from "oldText" to "long, long text" cannot be animated the way you want ; the animation is an image "morphing" animation, not a text substitution.

In your case, as sizeToFit is not a property for animation, the delay is not applied !

Test the following and see difference: prints after 4 seconds now.

    @IBAction func animate2LabelAction(_ sender: NSButton) {
        self.labelForAnimation.stringValue = "short text"
        NSAnimationContext.runAnimationGroup({ (context) in
            context.duration = 4.0
//            labelForAnimation.animator().sizeToFit()
            labelForAnimation.animator().alphaValue = 0.5  // This is animatable
        }, completionHandler: {
            print("Completion") } )
 
    }

Or add label change in completion:

    @IBAction func animate2LabelAction(_ sender: NSButton) {
        self.labelForAnimation.stringValue = "short text"
        NSAnimationContext.runAnimationGroup({ (context) in
            context.duration = 4.0
            //            labelForAnimation.animator().sizeToFit()
            labelForAnimation.animator().alphaValue = 0.5
        }, completionHandler: {
            self.labelForAnimation.stringValue = "long, long text"
            print("Completion") } )
 
    }

You can probably try something to get an approaching result.

• In the IBAction, create a hidden TextField, with same font as label1.
• Compute initialWidth, the original width of final text in this textField.

https://stackoverflow.com/questions/19128797/calculating-uilabel-text-size

• If initialWidth is larger than label1Width (label1), then apply the animation, with the following
• compute let scaleRatio = initialWidth / label1Width
• in the animation, apply a transform with this scale factor
• in the completion handler, set the finalText in label1 and sizeToFit()