Gradient not working on versions <= iOS 16

[xmollv]

Hello @TimOliver, thanks for such a great library! We've integrated it because we needed variable blurs on versions below iOS 26 to keep the UI consistent (more or less, you know...) between OS versions. We've realized that it works fine on iOS 26, iOS 18 and iOS 17, but on iOS 16 it doesn't. You just get a hard line rather than a gradient. Do you have any ideas on where the issue could be? I poked around a bit, but haven't found it yet!

Here's what I'm observing, see how on iOS 26 it creates a smooth gradient but on iOS 16 it's just a hard line:

And here's a sample project to reproduce it, would love to know if there's a way to make it work on versions older than iOS 17 (we support until iOS 15).

BlurKitSampleProject.zip

[TimOliver]

Hi there @xmollv! My pleasure! I'm so glad to hear you've found the library useful!

Oh wow! Thanks so much for such a detailed repro case! This might be the best issue I've ever been assigned. 😆

Thanks for letting me know! That's a really strange issue indeed. I was able to recreate it in the main sample app as well. As near as I can tell, it's simply how CISmoothLinearGradient and CILinearGradient seem to work on those older system versions.

I had a play with manually insetting the point0 value, and if I inset it to a sufficient amount, the hard edge goes away. Unfortunately, that sufficient value seems to vary depending on the size of the gradient. Not a great solution there. :/

I might have a play with replacing this Core Image logic with Core Graphics and see how that stacks up performance wise.

[TimOliver]

Okay just checked. I get the same hard edge using Core Graphics too. :(

I guess the best we can do is work out how much insetting is required to remove the hard edge and apply that on older iOS versions... Hopefully it's just a linear calculation

[TimOliver]

See if this works! #11

[xmollv]

@TimOliver Thanks you so much for looking into it so quickly!

I've just tested your branch but doesn't look like it changes much, I still see a hard edge on <= iOS 16. The following screenshot shows how it looks on iOS 17 (left), and iOS 16 (right):

[TimOliver]

Oh jeez. I might have been barking up the wrong tree. I had another play with it and found out it was due to the effect view's contentView having clipsToBounds being enabled. I turned it off, and it looks like that might have been enough to fix it.

I've added that to master now. Can you try that one and see how it looks?

[xmollv]

@TimOliver that seems to fix it, thank you so much! I'll double check tomorrow on the work project where we use it to ensure nothing broke there, but on the sample app I posted above seems to work fine on all iOS versions we needed (15 to 26!):

PS: I grabbed your changes by pointing to the main branch, but this should probably be a .1 release with the fix, right? Just a heads up!

[xmollv]

@TimOliver Just tested the main branch on the work project and works as expected on <= iOS 16 🎉! I'd love a 1.2.3 release since we have a very complex setup right now which prevents me from pointing to a branch from a Cocoapod's spec file, and that's how we're pulling this dependency right now!

Thanks again for the quick fix! ❤️

[TimOliver]

Woohoo! Looks lovely! I'm still not 100% happy about this. It feels like Apple enabled clipping on the effect view's contentView for a reason.

I might revisit this later on, but for now, I just pushed CocoaPods v1.2.3 which disables clipping which should solve the issue for now! Let me know if you have any trouble integrating it!

[xmollv]

@TimOliver Will do! I've just updated our app to pull 1.2.3 and I'll let you know once the QA team goes over it since I don't have devices on iOS 16/15. If the simulator was correct, on device probably will be too, but just in case! I'll ping you ASAP and if everything's fine we can close this issue.

Thanks again! 🙌🏼

[xmollv]

@TimOliver Got word from the QA team that works fine on iOS 15/16, thanks a ton again! ❤️

[TimOliver]

@xmollv Haha awesome to hear! My pleasure Xavi! All the best!