Permalink polish (#2771)

* Fix unbalanced padding.

* Animate the scroll to an event when it is already loaded.

* Perform the timeline clearance immediately before replacing the items.
Hides the empty timeline that was briefly shown.

* Make switching timeline more resilient.

ElementX/Sources/Services/Timeline/Fixtures/RoomTimelineItemFixtures.swift

@@ -20,7 +20,8 @@ enum RoomTimelineItemFixtures {
     /// The default timeline items used in Xcode previews etc.
     static var `default`: [RoomTimelineItemProtocol] = [
         SeparatorRoomTimelineItem(id: .init(timelineID: "Yesterday"), text: "Yesterday"),
-        TextRoomTimelineItem(id: .random,
+        TextRoomTimelineItem(id: .init(timelineID: ".RoomTimelineItemFixtures.default.0",
+                                       eventID: "RoomTimelineItemFixtures.default.0"),
                              timestamp: "10:10 AM",
                              isOutgoing: false,
                              isEditable: false,
@@ -29,7 +30,8 @@ enum RoomTimelineItemFixtures {
                              sender: .init(id: "", displayName: "Jacob"),
                              content: .init(body: "That looks so good!"),
                              properties: RoomTimelineItemProperties(isEdited: true)),
-        TextRoomTimelineItem(id: .random,
+        TextRoomTimelineItem(id: .init(timelineID: "RoomTimelineItemFixtures.default.1",
+                                       eventID: "RoomTimelineItemFixtures.default.1"),
                              timestamp: "10:11 AM",
                              isOutgoing: false,
                              isEditable: false,
@@ -40,7 +42,8 @@ enum RoomTimelineItemFixtures {
                              properties: RoomTimelineItemProperties(reactions: [
                                  AggregatedReaction(accountOwnerID: "me", key: "🙌", senders: [ReactionSender(id: "me", timestamp: Date())])
                              ])),
-        TextRoomTimelineItem(id: .random,
+        TextRoomTimelineItem(id: .init(timelineID: "RoomTimelineItemFixtures.default.2",
+                                       eventID: "RoomTimelineItemFixtures.default.2"),
                              timestamp: "10:11 AM",
                              isOutgoing: false,
                              isEditable: false,
@@ -59,7 +62,8 @@ enum RoomTimelineItemFixtures {
                                                     ])
                              ])),
         SeparatorRoomTimelineItem(id: .init(timelineID: "Today"), text: "Today"),
-        TextRoomTimelineItem(id: .random,
+        TextRoomTimelineItem(id: .init(timelineID: "RoomTimelineItemFixtures.default.3",
+                                       eventID: "RoomTimelineItemFixtures.default.3"),
                              timestamp: "5 PM",
                              isOutgoing: false,
                              isEditable: false,
@@ -68,7 +72,8 @@ enum RoomTimelineItemFixtures {
                              sender: .init(id: "", displayName: "Helena"),
                              content: .init(body: "Wow, cool. Ok, lets go the usual place tomorrow?! Is that too soon?  Here’s the menu, let me know what you want it’s on me!"),
                              properties: RoomTimelineItemProperties(orderedReadReceipts: [ReadReceipt(userID: "alice", formattedTimestamp: nil)])),
-        TextRoomTimelineItem(id: .random,
+        TextRoomTimelineItem(id: .init(timelineID: "RoomTimelineItemFixtures.default.4",
+                                       eventID: "RoomTimelineItemFixtures.default.4"),
                              timestamp: "5 PM",
                              isOutgoing: true,
                              isEditable: true,
@@ -76,7 +81,8 @@ enum RoomTimelineItemFixtures {
                              isThreaded: false,
                              sender: .init(id: "", displayName: "Bob"),
                              content: .init(body: "And John's speech was amazing!")),
-        TextRoomTimelineItem(id: .random,
+        TextRoomTimelineItem(id: .init(timelineID: "RoomTimelineItemFixtures.default.5",
+                                       eventID: "RoomTimelineItemFixtures.default.5"),
                              timestamp: "5 PM",
                              isOutgoing: true,
                              isEditable: true,
@@ -89,7 +95,8 @@ enum RoomTimelineItemFixtures {
                                                                                           ReadReceipt(userID: "bob", formattedTimestamp: nil),
                                                                                           ReadReceipt(userID: "charlie", formattedTimestamp: nil),
                                                                                           ReadReceipt(userID: "dan", formattedTimestamp: nil)])),
-        TextRoomTimelineItem(id: .random,
+        TextRoomTimelineItem(id: .init(timelineID: "RoomTimelineItemFixtures.default.6",
+                                       eventID: "RoomTimelineItemFixtures.default.6"),
                              timestamp: "5 PM",
                              isOutgoing: false,
                              isEditable: false,

ElementX/Sources/Services/Timeline/TimelineController/MockRoomTimelineController.swift

@@ -165,7 +165,7 @@ class MockRoomTimelineController: RoomTimelineControllerProtocol {
         
         let incomingItem = incomingItems.removeFirst()
         timelineItems.append(incomingItem)
-        callbacks.send(.updatedTimelineItems)
+        callbacks.send(.updatedTimelineItems(timelineItems: timelineItems, isSwitchingTimelines: false))
         
         try client?.send(.success)
     }
@@ -181,7 +181,7 @@ class MockRoomTimelineController: RoomTimelineControllerProtocol {
         
         let newItems = backPaginationResponses.removeFirst()
         timelineItems.insert(contentsOf: newItems, at: 0)
-        callbacks.send(.updatedTimelineItems)
+        callbacks.send(.updatedTimelineItems(timelineItems: timelineItems, isSwitchingTimelines: false))
         
         try client?.send(.success)
     }

ElementX/Sources/Services/Timeline/TimelineController/RoomTimelineController.swift

@@ -33,7 +33,7 @@ class RoomTimelineController: RoomTimelineControllerProtocol {
     private var activeTimeline: TimelineProxyProtocol
     private var activeTimelineProvider: RoomTimelineProviderProtocol {
         didSet {
-            configureActiveTimelineProvider(clearExistingItems: true)
+            configureActiveTimelineProvider()
         }
     }
     
@@ -272,31 +272,26 @@ class RoomTimelineController: RoomTimelineControllerProtocol {
     
     /// The cancellable used to update the timeline items.
     private var updateTimelineItemsCancellable: AnyCancellable?
+    /// The controller is switching the `activeTimelineProvider`.
+    private var isSwitchingTimelines = false
     
     /// Configures the controller to listen to `activeTimeline` for events.
     /// - Parameter clearExistingItems: Whether or not to clear any existing items before loading the timeline's contents.
-    private func configureActiveTimelineProvider(clearExistingItems: Bool = false) {
+    private func configureActiveTimelineProvider() {
+        updateTimelineItemsCancellable = nil
+        
+        isSwitchingTimelines = true
+        
+        // Inform the world that the initial items are loading from the store
+        callbacks.send(.paginationState(.init(backward: .paginating, forward: .paginating)))
+        callbacks.send(.isLive(activeTimelineProvider.isLive))
+        
         updateTimelineItemsCancellable = activeTimelineProvider
             .updatePublisher
             .receive(on: serialDispatchQueue)
             .sink { [weak self] items, paginationState in
                 self?.updateTimelineItems(itemProxies: items, paginationState: paginationState)
             }
-        
-        // Inform the world that the initial items are loading from the store
-        callbacks.send(.paginationState(.init(backward: .paginating, forward: .paginating)))
-        callbacks.send(.isLive(activeTimelineProvider.isLive))
-        
-        if clearExistingItems {
-            // Transition through empty to prevent animations.
-            timelineItems.removeAll()
-            callbacks.send(.updatedTimelineItems)
-        }
-        
-        serialDispatchQueue.async { [activeTimelineProvider] in
-            self.updateTimelineItems(itemProxies: activeTimelineProvider.itemProxies, paginationState: activeTimelineProvider.paginationState)
-            self.callbacks.send(.paginationState(.init(backward: .idle, forward: .idle)))
-        }
     }
     
     @objc private func contentSizeCategoryDidChange() {
@@ -309,6 +304,9 @@ class RoomTimelineController: RoomTimelineControllerProtocol {
     private func updateTimelineItems(itemProxies: [TimelineItemProxy], paginationState: PaginationState) {
         var newTimelineItems = [RoomTimelineItemProtocol]()
         
+        let isNewTimeline = isSwitchingTimelines
+        isSwitchingTimelines = false
+        
         let collapsibleChunks = itemProxies.groupBy { isItemCollapsible($0) }
         
         for (index, collapsibleChunk) in collapsibleChunks.enumerated() {
@@ -362,7 +360,7 @@ class RoomTimelineController: RoomTimelineControllerProtocol {
             timelineItems = newTimelineItems
         }
         
-        callbacks.send(.updatedTimelineItems)
+        callbacks.send(.updatedTimelineItems(timelineItems: newTimelineItems, isSwitchingTimelines: isNewTimeline))
         callbacks.send(.paginationState(paginationState))
     }
     

ElementX/Sources/Services/Timeline/TimelineController/RoomTimelineControllerProtocol.swift

@@ -19,7 +19,7 @@ import Foundation
 import UIKit
 
 enum RoomTimelineControllerCallback {
-    case updatedTimelineItems
+    case updatedTimelineItems(timelineItems: [RoomTimelineItemProtocol], isSwitchingTimelines: Bool)
     case paginationState(PaginationState)
     case isLive(Bool)
 }