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Fix a timeline jump triggered by pagination during an interactive scroll. (#2870)

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Doug 2024-05-21 09:19:25 +01:00 committed by GitHub
parent 711e36602e
commit 8027e665ad
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GPG Key ID: B5690EEEBB952194
1 changed files with 29 additions and 6 deletions
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35
ElementX/Sources/Screens/RoomScreen/View/Timeline/TimelineTableViewController.swift
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@ -59,8 +59,7 @@ class TimelineTableViewController: UIViewController {
var timelineStyle: TimelineStyle
var timelineItemsDictionary = OrderedDictionary<String, RoomTimelineItemViewState>() {
didSet {
if !isLive, isDraggingScrollView {
// Forward pagination doesn't play well with the user scrolling, so we wait for it to stop.
guard canApplySnapshot else {
hasPendingItems = true
return
}
@ -75,13 +74,34 @@ class TimelineTableViewController: UIViewController {
}
}
/// Whether or not it is safe to update the data source with the latest items.
private var canApplySnapshot: Bool {
if isLive {
// Backward pagination jumps if items are inserted whilst actively dragging.
!isDraggingScrollView
} else {
// Forward pagination breaks inertial scrolling when fixing the offset.
!scrollViewIsScrolling
}
}
/// There are pending items in `timelineItemsDictionary` that haven't been applied to the data source.
private var hasPendingItems = false
/// The user is dragging the scroll view (or it is still decelerating after a drag).
/// The scroll view is scrolling either directly with a drag or indirectly with inertia.
private var scrollViewIsScrolling = false {
didSet {
if !scrollViewIsScrolling, hasPendingItems, !isLive {
hasPendingItems = false
applySnapshot()
}
}
}
/// The scroll view is being dragged by the user (doesn't include scrolling with inertia)
private var isDraggingScrollView = false {
didSet {
if !isDraggingScrollView, hasPendingItems {
if !isDraggingScrollView, hasPendingItems, isLive {
hasPendingItems = false
applySnapshot()
}
@ -415,18 +435,21 @@ extension TimelineTableViewController: UITableViewDelegate {
func scrollViewWillBeginDragging(_ scrollView: UIScrollView) {
isDraggingScrollView = true
scrollViewIsScrolling = true
}
func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
sendLastVisibleItemReadReceipt()
isDraggingScrollView = false
if !decelerate {
isDraggingScrollView = false
scrollViewIsScrolling = false
}
}
func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
sendLastVisibleItemReadReceipt()
isDraggingScrollView = false
scrollViewIsScrolling = false
}
func scrollViewDidEndScrollingAnimation(_ scrollView: UIScrollView) {