AutoInsetter - Update contentOffset unexpectedly

[lowip]

New Issue Checklist

• [ x] Updated Tabman to the latest version
• [ x] I took a look at the Troubleshooting Guide
• [ x] I searched for existing GitHub issues

Issue Description

I have a TabmanViewController with the currentViewController having prefersStatusBarHidden set to true.
When selecting one of the cells in my currentViewController, a modal view controller is presented with prefersStatusBarHidden set to false.

This triggers a viewDidLayoutSubviews() -> setNeedsChildAutoInsetUpdate() -> autoInsetter.inset(...)

It goes in here: https://git.io/vhiyH

if scrollView.contentInset != requiredContentInset {
                  
  let isTopInsetChanged = requiredContentInset.top != scrollView.contentInset.top
  
  scrollView.contentInset = requiredContentInset
  scrollView.scrollIndicatorInsets = requiredContentInset
                  
  // only update contentOffset if the top contentInset has updated.
  if isTopInsetChanged {
      var contentOffset = scrollView.contentOffset
      contentOffset.y = -requiredContentInset.top // ⚠️We lose the current content offset here
      scrollView.contentOffset = contentOffset
  }
}

As you can see, the scrollView.contentOffset.y is updated regardless of the current contentOffset.

I propose the following change:

if scrollView.contentInset != requiredContentInset {
                
  let isTopInsetChanged = requiredContentInset.top != scrollView.contentInset.top
  let topInsetDelta = requiredContentInset.top - scrollView.contentInset.top
  
  scrollView.contentInset = requiredContentInset
  scrollView.scrollIndicatorInsets = requiredContentInset
                  
  // only update contentOffset if the top contentInset has updated.
  if isTopInsetChanged {
      var contentOffset = scrollView.contentOffset
      contentOffset.y -= topInsetDelta
      scrollView.contentOffset = contentOffset
  }
}

Which updates the contentOffset to the delta of the inset change.

I can prepare a pull request if need be.

Other useful things

A video of the issue: https://gfycat.com/PleasedIcyBichonfrise

[msaps]

@lowip great find! And thanks so much for the detailed report/fix.

I've opened a PR in AutoInsetter and will try to get a release done ASAP 🥇

[msaps]

@lowip released AutoInsetter 1.2.4 😄

_{Sent with GitHawk}

[lowip]

Great! Thanks for your reactivity, and your suite of libraries :)