signalapp/Signal-iOS
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Respond to CR.

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This commit is contained in:
Matthew Chen 2021-08-12 20:03:34 -03:00
parent c291aecfc1
commit 557247b944
2 changed files with 45 additions and 24 deletions
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67
Signal/src/ViewControllers/HomeView/HVTableDataSource.swift
View File

@ -22,6 +22,8 @@ public class HVTableDataSource: NSObject {
fileprivate var lastReloadDate: Date? { tableView.lastReloadDate }
fileprivate var lastPreloadCellDate: Date?
public required override init() {
super.init()
}
@ -73,12 +75,6 @@ extension HVTableDataSource {
extension HVTableDataSource: UIScrollViewDelegate {
public func scrollViewDidScroll(_ scrollView: UIScrollView) {
AssertIsOnMainThread()
preloadCellsIfNecessary()
}
private func preloadCellsIfNecessary() {
AssertIsOnMainThread()
@ -86,16 +82,29 @@ extension HVTableDataSource: UIScrollViewDelegate {
owsFailDebug("Missing viewController.")
return
}
let newContentOffset = tableView.contentOffset
defer {
viewController.lastKnownTableViewContentOffset = newContentOffset
guard viewController.hasEverAppeared else {
return
}
guard let oldContentOffset = viewController.lastKnownTableViewContentOffset else {
let newContentOffset = tableView.contentOffset
let oldContentOffset = viewController.lastKnownTableViewContentOffset
viewController.lastKnownTableViewContentOffset = newContentOffset
guard let oldContentOffset = oldContentOffset else {
return
}
let deltaY = (newContentOffset - oldContentOffset).y
guard deltaY != 0 else {
return
}
let isScrollingDownward = deltaY > 0
// Debounce.
let maxPreloadFrequency: TimeInterval = kSecondInterval / 100
if let lastPreloadCellDate = self.lastPreloadCellDate,
abs(lastPreloadCellDate.timeIntervalSinceNow) < maxPreloadFrequency {
return
}
lastPreloadCellDate = Date()
guard let visibleIndexPaths = tableView.indexPathsForVisibleRows else {
owsFailDebug("Missing visibleIndexPaths.")
return
@ -129,6 +138,7 @@ extension HVTableDataSource: UIScrollViewDelegate {
indexPathsToPreload.append(indexPath)
}
let preloadCount: Int = 3
if isScrollingDownward {
guard let lastIndexPath = sortedIndexPaths.last else {
owsFailDebug("Missing indexPath.")
@ -136,12 +146,11 @@ extension HVTableDataSource: UIScrollViewDelegate {
}
// Order matters; we want to preload in order of proximity
// to viewport.
tryToEnqueue(IndexPath(row: lastIndexPath.row + 1,
section: lastIndexPath.section))
tryToEnqueue(IndexPath(row: lastIndexPath.row + 2,
section: lastIndexPath.section))
tryToEnqueue(IndexPath(row: lastIndexPath.row + 3,
section: lastIndexPath.section))
for index in 0..<preloadCount {
let offset = +index
tryToEnqueue(IndexPath(row: lastIndexPath.row + offset,
section: lastIndexPath.section))
}
} else {
guard let firstIndexPath = sortedIndexPaths.first else {
owsFailDebug("Missing indexPath.")
@ -152,12 +161,11 @@ extension HVTableDataSource: UIScrollViewDelegate {
}
// Order matters; we want to preload in order of proximity
// to viewport.
tryToEnqueue(IndexPath(row: firstIndexPath.row - 1,
section: firstIndexPath.section))
tryToEnqueue(IndexPath(row: firstIndexPath.row - 2,
section: firstIndexPath.section))
tryToEnqueue(IndexPath(row: firstIndexPath.row - 3,
section: firstIndexPath.section))
for index in 0..<preloadCount {
let offset = -index
tryToEnqueue(IndexPath(row: firstIndexPath.row + offset,
section: firstIndexPath.section))
}
}
for indexPath in indexPathsToPreload {
@ -401,6 +409,8 @@ extension HVTableDataSource: UITableViewDelegate {
return
}
viewController?.updateCellVisibility(cell: cell, isCellVisible: true)
preloadCellsIfNecessary()
}
public func tableView(_ tableView: UITableView,
@ -877,7 +887,7 @@ extension HVTableDataSource {
return
}
let cacheKey = thread.uniqueId
if nil != cellContentCache.get(key: cacheKey) {
guard nil == cellContentCache.get(key: cacheKey) else {
// If we already have an existing HVCellContentToken, abort.
return
}
@ -892,6 +902,10 @@ extension HVTableDataSource {
// We use a serial queue to ensure we don't race and preload the same cell
// twice at the same time.
firstly(on: Self.preloadSerialQueue) { () -> (ThreadViewModel, HVCellContentToken) in
guard nil == cellContentCache.get(key: cacheKey) else {
// If we already have an existing HVCellContentToken, abort.
throw HVPreloadError.alreadyLoaded
}
// This is the expensive work we do off the main thread.
let threadViewModel = Self.databaseStorage.read { transaction in
ThreadViewModel(thread: thread, forHomeView: true, transaction: transaction)
@ -922,9 +936,16 @@ extension HVTableDataSource {
Logger.info("contentToken already loaded.")
}
}.catch(on: .global()) { error in
if case HVPreloadError.alreadyLoaded = error {
return
}
owsFailDebugUnlessNetworkFailure(error)
}
}
private enum HVPreloadError: Error {
case alreadyLoaded
}
}
// MARK: -

2
Signal/src/ViewControllers/HomeView/HomeViewCell.swift
View File

@ -276,7 +276,7 @@ public class HomeViewCell: UITableViewCell {
snippetLineHeight: snippetLineHeight)
}
internal func configure(cellContentToken: HVCellContentToken) {
func configure(cellContentToken: HVCellContentToken) {
AssertIsOnMainThread()
OWSTableItem.configureCell(self)