CATextLayer NSBackGroundColorAttributeName is there a way to make it works?

Question

I'm trying to make a CATextLayer accept NSBackGroundColorAttributeName the attribute in an attributed string?

   let mutableAttributed = NSMutableAttributedString(string: text , attributes: [
            NSForegroundColorAttributeName : UIColor.redColor(),
            NSBackgroundColorAttributeName : UIColor.whiteColor(),
            NSFontAttributeName :UIFont.systemFontOfSize(12)
            ])
    let textLayer = CATextLayer()
    textLayer.needsDisplayOnBoundsChange = true
    textLayer.string = mutableAttributed
    textLayer.bounds.size = CGSizeMake(200,200)

But it simply doesn't work, reading Stack I've found a reasonable answer but is pretty old, and it doesn't seems to be fully clear, if from iOS6 it should support it or not.

matt · Accepted Answer · 2016-07-03T15:13:23.363

2

The answer you pointed to is right. CATextLayer is very primitive and doesn't support this feature. Luckily, there is no need to use core text either; you can now use TextKit and just draw the string directly (and don't use CATextLayer at all).

class MyTextLayer : CALayer {
    @NSCopying var string : NSAttributedString?

    override func drawInContext(ctx: CGContext) {
        super.drawInContext(ctx)
        UIGraphicsPushContext(ctx)
        string?.drawWithRect(self.bounds,
            options: .UsesLineFragmentOrigin, context: nil)
        UIGraphicsPopContext()
    }
}

edited Jul 03 '16 at 15:13

answered Jul 03 '16 at 14:35

matt

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Sorry, I was just trying to assemble code from the original one, of course in the original I was setting the right property. I've update the answer. Thanks – Andrea Jul 03 '16 at 14:59
Added code showing how to build a CALayer that draws its own attributed text. – matt Jul 03 '16 at 15:13
Actually I can' t use a normal TextKit View, because I'm adding layers over a video composition. As far as I remember Apple explicitly say to do not use UIView's layer. Now I'm thinking to use your code or just enumerating string attributes, to set just the layer background. Many thanks – Andrea Jul 03 '16 at 15:36
2

The point is this. Back in the CATextLayer days, you had to use CoreText (and NSAttributedString was extremely hard to use; it wasn't really a native type on iOS). But an NSAttributedString nowadays knows how to draw itself (as my code shows). When it does that, you're using TextKit; to put another way, TextKit is the innovation that makes this possible, and that didn't happen until after the discussion you were looking at before. – matt Jul 03 '16 at 16:42

CATextLayer NSBackGroundColorAttributeName is there a way to make it works?

1 Answers1