Dynamically adjusting the visibleRoomsView's timeline limit based on …

ElementX/Sources/Screens/HomeScreen/HomeScreenModels.swift

@@ -14,6 +14,7 @@
 // limitations under the License.
 //
 
+import Combine
 import Foundation
 import UIKit
 
@@ -90,6 +91,8 @@ struct HomeScreenViewState: BindableState {
 struct HomeScreenViewStateBindings {
     var searchQuery = ""
 
+    var isScrolling = false
+
     var alertInfo: AlertInfo<UUID>?
 }
 

ElementX/Sources/Screens/HomeScreen/HomeScreenViewModel.swift

@@ -35,7 +35,7 @@ class HomeScreenViewModel: HomeScreenViewModelType, HomeScreenViewModelProtocol
 
     var callback: ((HomeScreenViewModelAction) -> Void)?
 
-    // swiftlint:disable:next function_body_length
+    // swiftlint:disable:next function_body_length cyclomatic_complexity
     init(userSession: UserSessionProtocol, attributedStringBuilder: AttributedStringBuilderProtocol) {
         self.userSession = userSession
         self.attributedStringBuilder = attributedStringBuilder
@@ -64,7 +64,17 @@ class HomeScreenViewModel: HomeScreenViewModelType, HomeScreenViewModelProtocol
             .debounce(for: 0.1, scheduler: DispatchQueue.main)
             .removeDuplicates()
             .sink { [weak self] range in
-                self?.updateVisibleRange(range)
+                guard let self else { return }
+
+                guard self.state.bindings.searchQuery.isEmpty else {
+                    return
+                }
+
+                if self.state.bindings.isScrolling {
+                    self.updateVisibleRange(range, timelineLimit: SlidingSyncConstants.lastMessageTimelineLimit)
+                } else {
+                    self.updateVisibleRange(range, timelineLimit: SlidingSyncConstants.timelinePrecachingTimelineLimit)
+                }
             }
             .store(in: &cancellables)
 
@@ -234,7 +244,7 @@ class HomeScreenViewModel: HomeScreenViewModelType, HomeScreenViewModelProtocol
         return room
     }
 
-    private func updateVisibleRange(_ range: Range<Int>) {
+    private func updateVisibleRange(_ range: Range<Int>, timelineLimit: UInt) {
         guard visibleRoomsSummaryProvider?.statePublisher.value == .live,
               !range.isEmpty else { return }
 
@@ -246,6 +256,6 @@ class HomeScreenViewModel: HomeScreenViewModelType, HomeScreenViewModelProtocol
         let lowerBound = max(0, range.lowerBound - Constants.slidingWindowBoundsPadding)
         let upperBound = min(Int(visibleRoomsSummaryProvider.countPublisher.value), range.upperBound + Constants.slidingWindowBoundsPadding)
 
-        visibleRoomsSummaryProvider.updateVisibleRange(lowerBound..<upperBound)
+        visibleRoomsSummaryProvider.updateVisibleRange(lowerBound..<upperBound, timelineLimit: timelineLimit)
     }
 }

ElementX/Sources/Screens/HomeScreen/View/HomeScreen.swift

@@ -19,14 +19,10 @@ import SwiftUI
 struct HomeScreen: View {
     @ObservedObject var context: HomeScreenViewModel.Context
 
+    @State private var scrollViewAdapter = ScrollViewAdapter()
     @State private var showingLogoutConfirmation = false
-    @State private var visibleItemIdentifiers = Set<String>() {
-        didSet {
-            if visibleItemIdentifiers != oldValue {
-                updateVisibleRange()
-            }
-        }
-    }
+    @State private var visibleItemIdentifiers = Set<String>()
+    @State private var hasTriggeredInitialVisibleItemUpdate = false
 
     var body: some View {
         ScrollView {
@@ -65,6 +61,10 @@ struct HomeScreen: View {
                 .disableAutocorrection(true)
             }
         }
+        .introspectScrollView { scrollView in
+            guard scrollView != scrollViewAdapter.scrollView else { return }
+            scrollViewAdapter.scrollView = scrollView
+        }
         .scrollDismissesKeyboard(.immediately)
         .disabled(context.viewState.roomListMode == .skeletons)
         .animation(.elementDefault, value: context.viewState.showSessionVerificationBanner)
@@ -76,6 +76,17 @@ struct HomeScreen: View {
                 userMenuButton
             }
         }
+        .onChange(of: visibleItemIdentifiers) { _ in
+            if !hasTriggeredInitialVisibleItemUpdate {
+                updateVisibleRange()
+                hasTriggeredInitialVisibleItemUpdate = true
+            }
+        }
+        .onReceive(scrollViewAdapter.isScrolling) { isScrolling in
+            context.isScrolling = isScrolling
+
+            updateVisibleRange()
+        }
         .background(Color.element.background)
     }
 

ElementX/Sources/Services/Client/ClientProxy.swift

@@ -259,7 +259,7 @@ class ClientProxy: ClientProxyProtocol {
             // Build the visibleRoomsSlidingSyncView here so that it can take advantage of the SS builder cold cache
             // We will still register the allRoomsSlidingSyncView later, and than will have no cache
             let visibleRoomsView = try SlidingSyncViewBuilder()
-                .timelineLimit(limit: 1)
+                .timelineLimit(limit: UInt32(SlidingSyncConstants.initialTimelineLimit)) // Starts off with zero to quickly load rooms, then goes to 1 while scrolling to quickly load last messages and 20 when the scrolling stops to load room history
                 .requiredState(requiredState: slidingSyncRequiredState)
                 .filters(filters: slidingSyncFilters)
                 .name(name: "CurrentlyVisibleRooms")
@@ -301,8 +301,8 @@ class ClientProxy: ClientProxyProtocol {
 
         // The allRoomsSlidingSyncView will be registered as soon as the visibleRoomsSlidingSyncView receives its first update
         visibleRoomsViewProxyStateObservationToken = visibleRoomsViewProxy.diffPublisher.sink { [weak self] _ in
-            MXLog.info("Visible rooms view received first update, registering all rooms view")
-            self?.registerAllRoomSlidingSyncView()
+            MXLog.info("Visible rooms view received first update, configuring views post initial sync")
+            self?.configureViewsPostInitialSync()
             self?.visibleRoomsViewProxyStateObservationToken = nil
         }
     }
@@ -349,13 +349,21 @@ class ClientProxy: ClientProxyProtocol {
                                                                         tags: [],
                                                                         notTags: [])
 
-    private func registerAllRoomSlidingSyncView() {
-        guard let allRoomsSlidingSyncView else {
+    private func configureViewsPostInitialSync() {
+        if let visibleRoomsSlidingSyncView {
+            MXLog.info("Setting visible rooms view timeline limit to \(SlidingSyncConstants.lastMessageTimelineLimit)")
+            visibleRoomsSlidingSyncView.setTimelineLimit(value: UInt32(SlidingSyncConstants.lastMessageTimelineLimit))
+        } else {
+            MXLog.error("Visible rooms sliding sync view unavailable")
+        }
+
+        if let allRoomsSlidingSyncView {
+            MXLog.info("Registering all rooms view")
+            _ = slidingSync?.addView(view: allRoomsSlidingSyncView)
+        } else {
             MXLog.error("All rooms sliding sync view unavailable")
-            return
         }
 
-        _ = slidingSync?.addView(view: allRoomsSlidingSyncView)
         restartSync()
     }
 

ElementX/Sources/Services/Client/ClientProxyProtocol.swift

@@ -58,6 +58,12 @@ enum PushFormat {
 //    }
 }
 
+enum SlidingSyncConstants {
+    static let initialTimelineLimit: UInt = 0
+    static let lastMessageTimelineLimit: UInt = 1
+    static let timelinePrecachingTimelineLimit: UInt = 20
+}
+
 protocol ClientProxyProtocol: AnyObject, MediaLoaderProtocol {
     var callbacks: PassthroughSubject<ClientProxyCallback, Never> { get }
 

ElementX/Sources/Services/Client/SlidingSyncViewProxy.swift

@@ -102,10 +102,11 @@ class SlidingSyncViewProxy {
         try slidingSync.getRoom(roomId: identifier)
     }
 
-    func updateVisibleRange(_ range: Range<Int>) {
-        MXLog.info("Setting sliding sync view range to \(range)")
+    func updateVisibleRange(_ range: Range<Int>, timelineLimit: UInt) {
+        MXLog.info("Setting sliding sync view range to \(range), timelineLimit: \(timelineLimit)")
 
         slidingSyncView.setRange(start: UInt32(range.lowerBound), end: UInt32(range.upperBound))
+        slidingSyncView.setTimelineLimit(value: UInt32(timelineLimit))
 
         visibleRangeUpdatePublisher.send(())
     }

ElementX/Sources/Services/Room/RoomSummary/MockRoomSummaryProvider.swift

@@ -44,7 +44,7 @@ class MockRoomSummaryProvider: RoomSummaryProviderProtocol {
         }
     }
 
-    func updateVisibleRange(_ range: Range<Int>) { }
+    func updateVisibleRange(_ range: Range<Int>, timelineLimit: UInt) { }
 
     // MARK: - Private
 

ElementX/Sources/Services/Room/RoomSummary/RoomSummaryProvider.swift

@@ -61,8 +61,8 @@ class RoomSummaryProvider: RoomSummaryProviderProtocol {
             .store(in: &cancellables)
     }
 
-    func updateVisibleRange(_ range: Range<Int>) {
-        slidingSyncViewProxy.updateVisibleRange(range)
+    func updateVisibleRange(_ range: Range<Int>, timelineLimit: UInt) {
+        slidingSyncViewProxy.updateVisibleRange(range, timelineLimit: timelineLimit)
     }
 
     // MARK: - Private

ElementX/Sources/Services/Room/RoomSummary/RoomSummaryProviderProtocol.swift

@@ -50,5 +50,5 @@ protocol RoomSummaryProviderProtocol {
     /// Publishes the total number of rooms
     var countPublisher: CurrentValueSubject<UInt, Never> { get }
 
-    func updateVisibleRange(_ range: Range<Int>)
+    func updateVisibleRange(_ range: Range<Int>, timelineLimit: UInt)
 }