scroll and pinch in multiple UiScrollViews at the same time - ios

Question

I have an UICollectionView with four custom cells. The cell's delegate is my main view which contains the collectionView and extends a custom cell delegate. Each cell contains a single UIScrollView which in turn contains and displays an UIImageView. For now, I can pinch and doubleTap to zoom in and out and move the image inside the cell's scrollViews.
I have in my application a "lock views" button that should lock the views together, so that if I pinch (zoom or move) in a cell, that change should be "copied" in the other cells. A 10% zoom increase in a cell should trigger a 10% zoom increase in all the others cells (independently to each cell current zoomScale). Similarly, a 10 unit movement to the left in one cell should move the others cells 10 units to the left.
I'm using scrollViewDidScroll(_ scrollView: UIScrollView) method to detect a change in my scrollViews and call my delegate which in turn have access to my others cells in my main UICollectionView
My first problem was that when I used UIScrollView.zoom(to : rect) or UIScrollView.zoomScale it would trigger again scrollViewDidScroll(_ scrollView: UIScrollView) in the others cells thus creating some king of infinite loop, but I managed to fix that by using :
var isZooming = false
func scrollViewCustomZoom(to rect: CGRect, animated : Bool ) {
isZooming = true
scrollView.zoom(to: rect, animated: animated)
isZooming = false
}
And :
func scrollViewDidScroll(_ scrollView: UIScrollView) {
if isZooming { return }
// do stuff, typically call the delegate
}
But now my problem is : what do I need to calculate in my scrollViewDidScroll method, and what do I need to set in each cell in my delegate in order you have the behavior I'm looking for?
I've already tried to play around scrollView.bounds, scrollView.origin or scrollView.size, but couldn't get the scaling factor to behave properly.
Any help would be most welcome and appreciated.

Answer 1

Found a solution to my own question. This solution does not call scrollViewDidScroll() in the others cells, which is exactly what I wanted.
Here is the trick :
// pinch-pan detection :
func scrollViewDidScroll(_ scrollView: UIScrollView) {
let newOrigin = scrollView.bounds.origin
let dx = newOrigin.x - currentScrollViewOrigin.x
let dy = newOrigin.y - currentScrollViewOrigin.y
let newScale = scrollView.zoomScale
let ds = newScale - currentZoomScale
if let d = delegate{
d.notifyMouvementInCell(self, dx: dx, dy: dy, ds: ds)
}
currentScrollViewOrigin = scrollView.bounds.origin
currentZoomScale = scrollView.zoomScale
}
In my delegate :
func notifyMouvementInCell(_ cell: customCell, dx: CGFloat, dy: CGFloat, ds: CGFloat){
if areViewsLocked{
for visibleCell in collectionView.visibleCells as! [IMECasesMultiDisplayCollectionViewCell]{
if visibleCell == cell { continue }
visibleCell.copyMouvementInForeignCell(horOffset: dx, vertOffset: dy, scaleOffset: ds)
}
}
}
And back in my cells :
func copyMouvementInForeignCell(horOffset dx: CGFloat, vertOffset dy: CGFloat, scaleOffset ds: CGFloat){
var newOrigin = scrollView.bounds.origin
newOrigin.x += dx
newOrigin.y += dy
scrollView.bounds.origin = newOrigin
var newScale = scrollView.zoomScale
newScale += ds
let affineTrans = CGAffineTransform(a: newScale, b: 0, c: 0, d: newScale, tx: 0, ty: 0)
// imageView is the view contained in each of my cell's scrollViews
imageView.layer.setAffineTransform(affineTrans)
currentZoomScale = scrollView.zoomScale
currentScrollViewOrigin = scrollView.bounds.origin
}
Hope this will help somebody someday !