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Merge branch 'mkirk/fix-photo-picker-ios10' into release/2.33.0

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Michael Kirk 2018-12-17 09:45:38 -07:00
commit 19d0119c6e
1 changed files with 26 additions and 14 deletions
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40
Signal/src/ViewControllers/PhotoLibrary/ImagePickerController.swift
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@ -155,20 +155,32 @@ class ImagePickerGridController: UICollectionViewController, PhotoLibraryDelegat
return
}
// We could try to be more precise by doing something like
//
// let botomOffset = collectionView.contentSize + collectionView.contentInset.top - collectionView.bounds.height
//
// But `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.
let bottomOffset = CGFloat.greatestFiniteMagnitude
collectionView.setContentOffset(CGPoint(x: 0, y: bottomOffset), animated: animated)
let verticalOffset: CGFloat
if #available(iOS 11, *) {
// 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 accesse colletionView.contentInset before `viewDidAppear`
// and calculate a precise content offset.
verticalOffset = CGFloat.greatestFiniteMagnitude
} else {
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
}
}
collectionView.setContentOffset(CGPoint(x: 0, y: verticalOffset), animated: animated)
}
private func reloadDataAndRestoreSelection() {