Don't update the timeline is the tab is not visible

Packages/Timeline/Sources/Timeline/TimelineView.swift

@@ -79,6 +79,7 @@ public struct TimelineView: View {
     .navigationTitle(timeline.localizedTitle())
     .navigationBarTitleDisplayMode(.inline)
     .onAppear {
+      viewModel.isTimelineVisible = true
       if viewModel.client == nil {
         viewModel.client = client
         viewModel.timeline = timeline
@@ -88,6 +89,9 @@ public struct TimelineView: View {
         }
       }
     }
+    .onDisappear {
+      viewModel.isTimelineVisible = false
+    }
     .refreshable {
       HapticManager.shared.impact(intensity: 0.3)
       await viewModel.fetchStatuses()

Packages/Timeline/Sources/Timeline/TimelineViewModel.swift

@@ -27,6 +27,7 @@ class TimelineViewModel: ObservableObject {
   }
 
   private var canStreamEvents: Bool = true
+  var isTimelineVisible: Bool = false
 
   let pendingStatusesObserver: PendingStatusesObserver = .init()
 
@@ -86,6 +87,7 @@ class TimelineViewModel: ObservableObject {
   func handleEvent(event: any StreamEvent, currentAccount _: CurrentAccount) {
     if let event = event as? StreamEventUpdate,
        canStreamEvents,
+       isTimelineVisible,
        pendingStatusesEnabled,
        !statuses.contains(where: { $0.id == event.status.id })
     {
@@ -212,13 +214,18 @@ extension TimelineViewModel: StatusesFetcher {
     
     ReblogCache.shared.removeDuplicateReblogs(&newStatuses)
 
-
     // If no new statuses, resume streaming and exit.
     guard !newStatuses.isEmpty else {
       canStreamEvents = true
       return
     }
     
+    // If the timeline is not visible, we don't update it as it would mess up the user position.
+    guard isTimelineVisible else {
+      canStreamEvents = true
+      return
+    }
+
     // Keep track of the top most status, so we can scroll back to it after view update.
     let topStatusId = statuses.first?.id