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Merge branch 'mkirk/fix-offset' into release/2.34.0

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This commit is contained in:
Michael Kirk 2019-01-22 09:07:24 -07:00
parent 710b80e566 870a7f292b
commit f5be0d545a
1 changed files with 20 additions and 31 deletions
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51
Signal/src/ViewControllers/PhotoLibrary/ImagePickerController.swift
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@ -120,6 +120,21 @@ class ImagePickerGridController: UICollectionViewController, PhotoLibraryDelegat
}
}
override func viewSafeAreaInsetsDidChange() {
if !hasEverAppeared {
// To scroll precisely to the bottom of the content, we have to account for the space
// taken up by the navbar and any notch.
//
// Before iOS11 the system accounts for this by assigning contentInset to the scrollView
// which is available by the time `viewWillAppear` is called.
//
// On iOS11+, contentInsets are not assigned to the scrollView in `viewWillAppear`, but
// this method, `viewSafeAreaInsetsDidChange` is called *between* `viewWillAppear` and
// `viewDidAppear` and indicates `safeAreaInsets` have been assigned.
scrollToBottom(animated: false)
}
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
@ -157,38 +172,12 @@ class ImagePickerGridController: UICollectionViewController, PhotoLibraryDelegat
return
}
var verticalOffset: CGFloat
let visibleHeight = collectionView.bounds.height - collectionView.contentInset.top
let contentHeight = collectionView.contentSize.height
if contentHeight <= visibleHeight {
verticalOffset = -collectionView.contentInset.top
} else {
let topOfLastPage = contentHeight - collectionView.bounds.height
verticalOffset = topOfLastPage
let lastSection = collectionView.numberOfSections - 1
let lastItem = collectionView.numberOfItems(inSection: lastSection) - 1
if lastSection >= 0 && lastItem >= 0 {
let lastIndex = IndexPath(item: lastItem, section: lastSection)
collectionView.scrollToItem(at: lastIndex, at: .bottom, animated: animated)
}
if #available(iOS 11, *) {
if hasEverAppeared {
verticalOffset += collectionView.safeAreaInsets.bottom
} else {
// On iOS10 and earlier, we can be precise, but as of iOS11 `collectionView.contentInset`
// is based on `safeAreaInsets`, which isn't accurate until `viewDidAppear` at the earliest.
//
// from https://developer.apple.com/documentation/uikit/uiview/positioning_content_relative_to_the_safe_area
// > Make your modifications in [viewDidAppear] because the safe area insets for a view are
// > not accurate until the view is added to a view hierarchy.
//
// Overshooting like this works without visible animation glitch. on iOS11+
// However, before iOS11, "overshooting" the contentOffset like this produces a broken
// layout or hanging. Luckily for those versions, before the safeAreaInset feature
// existed, we can accurately access collectionView.contentInset before `viewDidAppear`
// and calculate a precise content offset.
verticalOffset += 122
}
}
collectionView.setContentOffset(CGPoint(x: 0, y: verticalOffset), animated: animated)
}
private func reloadDataAndRestoreSelection() {