forked from shadowfacts/Tusker
Completely replace all items when jumping to present
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parent
0485400c1f
commit
80f9800fd6
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@ -343,21 +343,19 @@ class TimelineViewController: UIViewController, TimelineLikeCollectionViewContro
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}
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}
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private func insertPresentItemsIfNecessary(_ presentItems: [String]) {
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private func insertPresentItemsIfNecessary(_ presentItems: [String]) {
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var snapshot = dataSource.snapshot()
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let snapshot = dataSource.snapshot()
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guard snapshot.indexOfSection(.statuses) != nil else {
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guard snapshot.indexOfSection(.statuses) != nil else {
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return
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return
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}
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}
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let currentItems = snapshot.itemIdentifiers(inSection: .statuses)
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let currentItems = snapshot.itemIdentifiers(inSection: .statuses)
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if case .status(id: let firstID, state: _) = currentItems.first,
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if case .status(id: let firstID, state: _) = currentItems.first,
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// if there's no overlap between presentItems and the existing items in the data source, insert the present items and prompt the user
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// if there's no overlap between presentItems and the existing items in the data source, prompt the user
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!presentItems.contains(firstID) {
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!presentItems.contains(firstID) {
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// remove any existing gap, if there is one
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// create a new snapshot to reset the timeline to the "present" state
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if let index = currentItems.lastIndex(of: .gap) {
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var snapshot = NSDiffableDataSourceSnapshot<Section, Item>()
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snapshot.deleteItems(Array(currentItems[index...]))
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snapshot.appendSections([.statuses])
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}
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snapshot.appendItems(presentItems.map { .status(id: $0, state: .unknown) }, toSection: .statuses)
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snapshot.insertItems([.gap], beforeItem: currentItems.first!)
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snapshot.insertItems(presentItems.map { .status(id: $0, state: .unknown) }, beforeItem: .gap)
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var config = ToastConfiguration(title: "Jump to present")
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var config = ToastConfiguration(title: "Jump to present")
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config.edge = .top
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config.edge = .top
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@ -366,12 +364,34 @@ class TimelineViewController: UIViewController, TimelineLikeCollectionViewContro
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config.action = { [unowned self] toast in
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config.action = { [unowned self] toast in
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toast.dismissToast(animated: true)
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toast.dismissToast(animated: true)
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let origSnapshot = self.dataSource.snapshot()
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let origItemAtTop: (Item, CGFloat)?
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if let statusesSection = origSnapshot.indexOfSection(.statuses),
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let indexPath = self.collectionView.indexPathsForVisibleItems.sorted().first(where: { $0.section == statusesSection }),
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let cell = self.collectionView.cellForItem(at: indexPath),
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let item = self.dataSource.itemIdentifier(for: indexPath) {
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origItemAtTop = (item, cell.convert(.zero, to: self.view).y - self.view.safeAreaInsets.top)
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} else {
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origItemAtTop = nil
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}
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self.dataSource.apply(snapshot, animatingDifferences: true) {
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self.dataSource.apply(snapshot, animatingDifferences: true) {
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// TODO: we can't set prevScrollOffsetBeforeScrollToTop here to allow undoing the scroll-to-top
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// because that would involve scrolling through unmeasured-cell which fucks up the content offset values.
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// we probably need a data-source aware implementation of scrollToTop which uses item & offset w/in item
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// to track the restore position
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self.collectionView.scrollToItem(at: IndexPath(row: 0, section: 0), at: .top, animated: true)
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self.collectionView.scrollToItem(at: IndexPath(row: 0, section: 0), at: .top, animated: true)
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var config = ToastConfiguration(title: "Go back")
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config.edge = .top
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config.systemImageName = "arrow.down"
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config.dismissAutomaticallyAfter = 4
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config.action = { [unowned self] toast in
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toast.dismissToast(animated: true)
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// todo: it would be nice if we could animate this, but that doesn't work with the screen-position-maintaining stuff
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if let (item, offset) = origItemAtTop {
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self.applySnapshot(snapshot, maintainingScreenPosition: offset, ofItem: item)
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} else {
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self.dataSource.apply(origSnapshot, animatingDifferences: false)
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}
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}
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self.showToast(configuration: config, animated: true)
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}
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}
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}
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}
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self.showToast(configuration: config, animated: true)
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self.showToast(configuration: config, animated: true)
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@ -380,32 +400,35 @@ class TimelineViewController: UIViewController, TimelineLikeCollectionViewContro
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// NOTE: this only works when items are being inserted ABOVE the item to maintain
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// NOTE: this only works when items are being inserted ABOVE the item to maintain
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private func applySnapshot(_ snapshot: NSDiffableDataSourceSnapshot<Section, Item>, maintainingBottomRelativeScrollPositionOf itemToMaintain: Item) {
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private func applySnapshot(_ snapshot: NSDiffableDataSourceSnapshot<Section, Item>, maintainingBottomRelativeScrollPositionOf itemToMaintain: Item) {
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// use a snapshot of the collection view to hide the flicker as the content offset changes and then changes back
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let snapshotView = collectionView.snapshotView(afterScreenUpdates: false)!
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snapshotView.layer.zPosition = 1000
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snapshotView.frame = view.bounds
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view.addSubview(snapshotView)
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var firstItemAfterOriginalGapOffsetFromTop: CGFloat = 0
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var firstItemAfterOriginalGapOffsetFromTop: CGFloat = 0
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if let indexPath = dataSource.indexPath(for: itemToMaintain),
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if let indexPath = dataSource.indexPath(for: itemToMaintain),
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let cell = collectionView.cellForItem(at: indexPath) {
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let cell = collectionView.cellForItem(at: indexPath) {
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// subtract top safe area inset b/c scrollToItem at .top aligns the top of the cell to the top of the safe area
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// subtract top safe area inset b/c scrollToItem at .top aligns the top of the cell to the top of the safe area
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firstItemAfterOriginalGapOffsetFromTop = cell.convert(.zero, to: view).y - view.safeAreaInsets.top
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firstItemAfterOriginalGapOffsetFromTop = cell.convert(.zero, to: view).y - view.safeAreaInsets.top
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}
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}
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applySnapshot(snapshot, maintainingScreenPosition: firstItemAfterOriginalGapOffsetFromTop, ofItem: itemToMaintain)
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}
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private func applySnapshot(_ snapshot: NSDiffableDataSourceSnapshot<Section, Item>, maintainingScreenPosition offsetFromTop: CGFloat, ofItem itemToMaintain: Item) {
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// use a snapshot of the collection view to hide the flicker as the content offset changes and then changes back
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let snapshotView = collectionView.snapshotView(afterScreenUpdates: false)!
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snapshotView.layer.zPosition = 1000
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snapshotView.frame = view.bounds
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view.addSubview(snapshotView)
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dataSource.apply(snapshot, animatingDifferences: false) {
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dataSource.apply(snapshot, animatingDifferences: false) {
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if let indexPathOfItemAfterOriginalGap = self.dataSource.indexPath(for: itemToMaintain) {
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if let indexPathOfItemToMaintain = self.dataSource.indexPath(for: itemToMaintain) {
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// scroll up until we've accumulated enough MEASURED height that we can put the
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// scroll up until we've accumulated enough MEASURED height that we can put the
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// firstItemAfterOriginalGapCell at the top of the screen and then scroll down by
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// firstItemAfterOriginalGapCell at the top of the screen and then scroll down by
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// firstItemAfterOriginalGapOffsetFromTop without intruding into unmeasured area
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// firstItemAfterOriginalGapOffsetFromTop without intruding into unmeasured area
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var cur = indexPathOfItemAfterOriginalGap
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var cur = indexPathOfItemToMaintain
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var amountScrolledUp: CGFloat = 0
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var amountScrolledUp: CGFloat = 0
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while true {
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while true {
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if cur.row <= 0 {
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if cur.row <= 0 {
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break
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break
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}
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}
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if let cell = self.collectionView.cellForItem(at: indexPathOfItemAfterOriginalGap),
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if let cell = self.collectionView.cellForItem(at: indexPathOfItemToMaintain),
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cell.convert(.zero, to: self.view).y - self.view.safeAreaInsets.top > firstItemAfterOriginalGapOffsetFromTop {
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cell.convert(.zero, to: self.view).y - self.view.safeAreaInsets.top > offsetFromTop {
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break
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break
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}
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}
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cur = IndexPath(row: cur.row - 1, section: cur.section)
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cur = IndexPath(row: cur.row - 1, section: cur.section)
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@ -415,7 +438,7 @@ class TimelineViewController: UIViewController, TimelineLikeCollectionViewContro
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amountScrolledUp += attrs.size.height
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amountScrolledUp += attrs.size.height
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}
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}
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self.collectionView.contentOffset.y += amountScrolledUp
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self.collectionView.contentOffset.y += amountScrolledUp
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self.collectionView.contentOffset.y -= firstItemAfterOriginalGapOffsetFromTop
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self.collectionView.contentOffset.y -= offsetFromTop
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}
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}
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snapshotView.removeFromSuperview()
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snapshotView.removeFromSuperview()
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