vertically align text in a CATextLayer?

Question

I am working on a CATextLayer that I want to use in both Mac and iOS. Can I control the vertical alignment of the text within the layer?

In this particular case, I

Answer 1

I slightly modified this answer by @iamkothed. The differences are:

• text height calculation is based on NSString.size(with: Attributes). I don't know if it's an improvement over (height-fontSize)/2 - fontSize/10, but I like to think that it is. Although, in my experience, NSString.size(with: Attributes) doesn't always return the most appropriate size.
• added invertedYAxis property. It was useful for my purposes of exporting this CATextLayer subclass using AVVideoCompositionCoreAnimationTool. AVFoundation operates in "normal" y axis, and that's why I had to add this property.
• Works only with NSString. You can use Swift's String class though, because it automatically casts to NSString.

• It ignores CATextLayer.fontSize property and completely relies on CATextLayer.font property which MUST be a UIFont instance.

  class VerticallyCenteredTextLayer: CATextLayer {
      var invertedYAxis: Bool = true
  
      override func draw(in ctx: CGContext) {
          guard let text = string as? NSString, let font = self.font as? UIFont else {
              super.draw(in: ctx)
              return
          }
  
          let attributes = [NSAttributedString.Key.font: font]
          let textSize = text.size(withAttributes: attributes)
          var yDiff = (bounds.height - textSize.height) / 2
          if !invertedYAxis {
              yDiff = -yDiff
          }
          ctx.saveGState()
          ctx.translateBy(x: 0.0, y: yDiff)
          super.draw(in: ctx)
          ctx.restoreGState()
      }
  }