UIScrollView in UITableViewCell doesn't zoom at touch origin - ios

Question

I have a UIScrollView inside a UITableViewCell to allow zooming on a UIWebView inside the cell. When the view is zoomed in, the UITableViewCell is enlarged to fit the new size of the web view after being zoomed in. This is being done by changing the height constraint on the UIScrollView and implementing UITableView's automatic row height.
The issue right now is that zooming inside the scroll view does not zoom at the origin of the pinch, but somewhere above, so the view does not get zoomed in where the user intended.
Here is the view hierarchy:
[UITableView]
[CustomUITableViewCell]
[UIView] (Content View)
[UIView]
[UIScrollView]
[UIWebView]
[UIView]
The cell is both a UIWebViewDelegate and a UIScrollViewDelegate:
Custom UITableViewCell:
func configure() { // Called from tableView:cellForRowAt:
scrollView.delegate = self
webView.delegate = self
webView.scrollView.isScrollEnabled = false
webView.scalesPageToFit = true
webView.scrollView.bounces = false
webView.scrollView.clipsToBounds = false
let htmlTemplate = TableViewCell.messageTemplate
webView.loadHTMLString(htmlTemplate, baseURL: Bundle.main.bundleURL)
}
// UIScrollViewDelegate
func viewForZooming(in scrollView: UIScrollView) -> UIView? {
return webView
}
func scrollViewDidZoom(_ scrollView: UIScrollView) {
updateWebViewFrame()
scrollViewHeightConstraint.constant = webView.frame.height
layoutIfNeeded()
delegate?.updateCellHeights()
}
The table's view controller is the delegate for the cell, which implements updateCellHeights:
func updateCellHeights() {
// https://stackoverflow.com/a/30110230/482536
let offset = tableView.contentOffset
tableView.beginUpdates()
tableView.endUpdates()
tableView.layer.removeAllAnimations()
tableView.setContentOffset(offset, animated: false)
}
How do I make the scroll view zoom to the pinch origin?
Is this even the right approach to this problem? I tried using the scrollView inside the UIWebView directly, but couldn't get the UIWebView to resize to the inner scrollView correctly.