I have an app which supports both iOS10 and iOS11. In the app I have a uiview pinned to a finger via pan gesture. Pan gesture moves view center only along y axis (x stays the same always). I also have CGAffineTransform tied to the gesture, the more up user moves my view the larger it becomes. "Panned" view contains another view with some content.
Now on iOS11 I have this behavoiur (which I consider correct):
> - center of content view stays on a vertical line
^ <--[ | ]-->
| <----[ | ]---->
| <------[ | ]------>
| <--------[ ]-------->
But on iOS10 I get this behavoiur:
> - center of content view moves to the right along with scale growth
^ <----[ / ]>
| <-----[ / ]--->
| <------[ / ]------>
| <--------[ ]-------->
My code to add content view to panned view:
// self is PannedView
self.addSubview(contentView)
contentView.translatesAutoresizingMaskIntoConstraints = false
// add constraints:
// self.width = contentView.width
// self.height = contentView.height
// self.centerX = contentView.centerX
// self.centerY = contentView.centerY
Handle pan gesture:
... // handle some unrelated stuff
panView.center.y = self.panStartPoint.y + panDeltaY // where panDeltaY is basically a translation of a UIPanGestureRecognizer
... // some scale calculation logic, calc scale addition depending on pan touch location
let scale = 1 + movePercent * 0.1 // where movePercent is between 0 and 1
panView.transform = CGAffineTransform.identity.scaledBy(x: scale, y: scale)
As you can see I also cap scale to be between 1 and 1.1.
It seems like either constraints in conjunction with scaling work differently on iOS10 and iOS11 or scaling is "double" propagated to subviews somehow.
Any ideas?
Don't apply a transform to a view that is positioned by constraints. The results are undefined (which is exactly what you are experiencing: it "means" one thing on one system and another thing another).