Feed rendering improvements (#53)

## Summary

This change improves Feed screen rendering and scrolling performance.

## What was done

- [x] Preserve `StatusReducer.State` when reloading statuses.
- [x] Update status rendering. Only render HTML to AttributedString when
the HTML intended to be displayed changes for the status displayed on
the screen.

Projects/App/AppFeature/Sources/App.swift

@@ -33,7 +33,7 @@ struct App: SwiftUI.App {
       case .feed(.status(.element(_, .view(.linkTapped(_))))): true
       case .feed(.status(.element(_, .view(.previewCardTapped)))): true
       case .feed(.status(.element(_, .view(.quickLookItemChanged(_))))): true
-      case .feed(.status(.element(_, .view(.textTask)))): false
+      case .feed(.status(.element(_, .view(.textSourceChanged)))): false
       case .feed(.view(.refreshButtonTapped)): true
       case .feed(.view(.refreshTask)): true
       case .feed(.view(.seeMoreButtonTapped)): true

Projects/App/FeedFeature/Sources/FeedReducer.swift

@@ -65,8 +65,12 @@ public struct FeedReducer: Reducer, Sendable {
         state.isLoading = false
         switch result {
         case .success(let statuses):
-          state.statuses = .init(
-            uniqueElements: statuses.map { StatusReducer.State(status:$0) }
+          state.statuses = IdentifiedArray(
+            uniqueElements: statuses.map { status in
+              var state = state.statuses[id: status.id] ?? StatusReducer.State(status: status)
+              state.status = status
+              return state
+            }
           )
 
         case .failure(_):

Projects/App/FeedFeature/Sources/StatusReducer.swift

@@ -25,6 +25,10 @@ public struct StatusReducer: Reducer, Sendable {
       status.reblog?.value ?? status
     }
 
+    var textSource: String {
+      displayStatus.content
+    }
+
     var attachments: IdentifiedArrayOf<MediaAttachment> {
       var attachments = IdentifiedArrayOf<MediaAttachment>()
       attachments.append(contentsOf: status.mediaAttachments)
@@ -50,7 +54,7 @@ public struct StatusReducer: Reducer, Sendable {
       case linkTapped(URL)
       case previewCardTapped
       case quickLookItemChanged(URL?)
-      case textTask
+      case textSourceChanged
     }
   }
 
@@ -66,14 +70,14 @@ public struct StatusReducer: Reducer, Sendable {
         return .none
 
       case .renderText:
-        let html = state.displayStatus.content
+        let html = state.textSource
         return .run { send in
           let result = Result { try render(html) }
           await send(.textRendered(result))
         }
 
       case .textRendered(.failure(_)):
-        state.text = AttributedString(state.displayStatus.content)
+        state.text = AttributedString(state.textSource)
         return .none
 
       case .textRendered(.success(let text)):
@@ -118,11 +122,8 @@ public struct StatusReducer: Reducer, Sendable {
         state.quickLookItem = url
         return .none
 
-      case .view(.textTask):
-        if state.text == nil {
-          return .send(.renderText)
-        }
-        return .none
+      case .view(.textSourceChanged):
+        return .send(.renderText)
       }
     }
     .ifLet(\.$quickLookItem, action: \.quickLookItem) {

Projects/App/FeedFeature/Sources/StatusView.swift

@@ -42,8 +42,9 @@ public struct StatusView: View {
     Text(text)
       .redacted(reason: isPlaceholder ? .placeholder : [])
       .disabled(isPlaceholder)
-      .onChange(of: isPlaceholder, initial: true) { _, isPlaceholder in
-        if isPlaceholder { send(.textTask) }
+      .onChange(of: store.textSource, initial: true) { old, new in
+        guard old != new || store.text == nil else { return }
+        send(.textSourceChanged)
       }
       .environment(\.openURL, OpenURLAction { url in
         send(.linkTapped(url))

Projects/App/FeedFeature/Tests/FeedReducerTests.swift

@@ -107,4 +107,34 @@ final class FeedReducerTests: XCTestCase {
       FeedReducer.mastodonAccountURL
     ])
   }
+
+  @MainActor func testReloadStatusesPreservesTheirStates() async {
+    let statuses = Array([Status].preview[0...2])
+    let store = TestStore(initialState: FeedReducer.State(
+      statuses: [
+        StatusReducer.State(
+          status: statuses[0],
+          text: "Status 0 text"
+        ),
+        StatusReducer.State(
+          status: statuses[1],
+          text: "Status 1 text"
+        ),
+        StatusReducer.State(
+          status: statuses[2],
+          text: "Status 2 text"
+        ),
+      ],
+      isLoading: true
+    )) {
+      FeedReducer()
+    } withDependencies: {
+      $0.continuousClock = ImmediateClock()
+      $0.mastodon.getAccountStatuses.send = { _ in [] }
+    }
+
+    await store.send(.fetchStatusesResult(.success(statuses))) {
+      $0.isLoading = false
+    }
+  }
 }

Projects/App/FeedFeature/Tests/StatusReducerTests.swift

@@ -223,14 +223,12 @@ final class StatusReducerTests: XCTestCase {
       }
     }
 
-    await store.send(.view(.textTask))
+    await store.send(.view(.textSourceChanged))
     await store.receive(\.renderText)
     expectNoDifference(didRender.value, [status.content])
     await store.receive(\.textRendered.success) {
       $0.text = renderedText
     }
-
-    await store.send(.view(.textTask))
   }
 
   @MainActor func testTextRenderingFailure() async {
@@ -245,7 +243,7 @@ final class StatusReducerTests: XCTestCase {
       $0.statusTextRenderer.render = { _ in throw failure }
     }
 
-    await store.send(.view(.textTask))
+    await store.send(.view(.textSourceChanged))
     await store.receive(\.renderText)
     await store.receive(\.textRendered.failure) {
       $0.text = AttributedString(status.content)

README.md

@@ -97,7 +97,7 @@ The project is integrated with [Xcode Cloud](https://developer.apple.com/xcode-c
 
 ## 🛠 Develop
 
-- Use Xcode (version ≥ 15.4).
+- Use Xcode (version ≥ 16.0).
 - Clone the repository or create a fork & clone it.
 - Run `setup_for_development.sh` script to generate Xcode workspace and set everything up for development:
     ```sh