Graphic distortion with invisible rotating sprite on layer above an HTML layer in iOS v >26.2.1

I noticed a project I’m working on exhibited blocky/flashing distortion when exported to iOS 26.4.2. I checked and noticed it also happened in Safari on the same device – an iPhone SE 2nd Gen. I have another SE running 26.2.1 and the issue didn’t happen. I updated both to 26.5 and it’s now reproduced on both devices, so I’m guessing maybe some kind of webkit regression since 26.2.1?

When I stripped the project down, I narrowed the cause to having an invisible sprite with rotation enabled on a normal layer above an HTML layer!

This project shows the issue. It should just show three “PLAY” buttons at the bottom of the screen, but since 26.2.1, they glitch out/flash.

https://drive.google.com/file/d/1HlojvMzGmIbESIVr_Meyjj3aeQTYmF5B/view?usp=sharing

It’s such a specific set of circumstances that caused the issue in my case (and something I’ve easily worked around) that I thought I’d post here first in case anyone’s had similar issues that might help narrow down the root cause.

Small update:

Also updated my iPad to 26.5 and that's now showing the issue too.

I don't think it's specifically caused by the rotate behaviour - it seems like having anything doing something on a layer above screws things up.

I did see this error in Xcode's console when running on my iPad (transitioning to a layout that has an HTML layer):

WebContent[1365] 0x10e058100 - [sessionID=1] WebProcess::markAllLayersVolatile: Failed to mark layers as volatile for webPageID=19

Fortunately, I don't think I actually need HTML layers in this project any more (as I've reduced the number of HTML elements I'm using). I've reverted them to normal layers and the graphical glitches are gone - just double checking everthing else looks fine with the HTML layers.

Made no difference. I've worked around it but if I get a chance I'll try troubleshooting further and log a bug.

I have this problem too. The solution for me was to untick HTML Layer. It wasn't needed in my case.

But if HTML Layer is needed Construct team need to do something to fix the problem.

Please make a bug report on the github link in the post above.

Ashley needs to fix this

I have this problem too. The solution for me was to untick HTML Layer. It wasn't needed in my case.

But if HTML Layer is needed Construct team need to do something to fix the problem.

Please make a bug report on the github link in the post above.

Ashley needs to fix this

Be good if you could add specifics or your issue here:

github.com/Scirra/Construct-bugs/issues/9106

> I have this problem too. The solution for me was to untick HTML Layer. It wasn't needed in my case.

> But if HTML Layer is needed Construct team need to do something to fix the problem.

>

> Please make a bug report on the github link in the post above.

> Ashley needs to fix this

Be good if you could add specifics or your issue here:

https://github.com/Scirra/Construct-bugs/issues/9106

paala

Ashley pointed out that this had already been raised here:

https://github.com/Scirra/Construct-bugs/issues/9057

And he's raised it on the webkit issues board here:

https://bugs.webkit.org/show_bug.cgi?id=312987

I've just commented on that - so if you could too, it might bump its urgency.