Improve projection performance

World Manager for Minecraft/Services/Sources/Core/SourceLibrary.swift

@@ -26,7 +26,11 @@ final class SourceLibrary: ObservableObject, SourceScanSessionHosting, SourcePer
         category: "ConnectedDevicePerformance"
     )
 
-    @Published var sources: [MinecraftSource] = []
+    @Published var sources: [MinecraftSource] = [] {
+        didSet {
+            rebuildLookupIndexes()
+        }
+    }
     @Published var connectedDevices: [ConnectedDeviceSidebarEntry] = []
     @Published var isRestoringPersistedSources = true
 
@@ -40,6 +44,8 @@ final class SourceLibrary: ObservableObject, SourceScanSessionHosting, SourcePer
     private let notificationService: ScanNotificationServicing
     private let itemActionService: ContentItemActionService
     private let connectedDeviceSourceFactory = ConnectedDeviceSourceFactory()
+    private var sourceIndexByID: [URL: Int] = [:]
+    private var sourceIDByItemID: [URL: URL] = [:]
     var lastMatchedConnectedSourceIDs: Set<URL> = []
     var cachedDeviceDiscoveryByUDID: [String: CachedConnectedDeviceDiscovery] = [:]
     var isShuttingDown = false
@@ -90,6 +96,14 @@ final class SourceLibrary: ObservableObject, SourceScanSessionHosting, SourcePer
         visibleSources
     }
 
+    func sourceID(forItemID itemID: URL) -> URL? {
+        sourceIDByItemID[itemID]
+    }
+
+    func containsItem(withID itemID: URL) -> Bool {
+        sourceIDByItemID[itemID] != nil
+    }
+
     func shutdown() {
         guard !isShuttingDown else {
             return
@@ -189,7 +203,11 @@ final class SourceLibrary: ObservableObject, SourceScanSessionHosting, SourcePer
     }
 
     func source(withID sourceID: URL) -> MinecraftSource? {
-        sources.first(where: { $0.id == sourceID })
+        guard let index = sourceIndexByID[sourceID], sources.indices.contains(index) else {
+            return nil
+        }
+
+        return sources[index]
     }
 
     func rescanSource(withID sourceID: URL) {
@@ -499,6 +517,18 @@ final class SourceLibrary: ObservableObject, SourceScanSessionHosting, SourcePer
         )
     }
 
+    private func rebuildLookupIndexes() {
+        sourceIndexByID = Dictionary(uniqueKeysWithValues: sources.enumerated().map { ($0.element.id, $0.offset) })
+
+        var itemIndex: [URL: URL] = [:]
+        for source in sources {
+            for item in source.items {
+                itemIndex[item.id] = source.id
+            }
+        }
+        sourceIDByItemID = itemIndex
+    }
+
     @discardableResult
     func updateAvailability(for sourceID: URL, to newAvailability: SourceAvailability) -> (previous: SourceAvailability, becameAvailable: Bool) {
         SourceSyncRuntime.updateAvailability(for: sourceID, to: newAvailability, on: self)

World Manager for Minecraft/UI/List/ItemListColumnViews.swift

@@ -33,7 +33,7 @@ struct ItemListColumnView<MenuContent: View>: View {
     let subtitle: String
     let showsSubtitle: Bool
     let isRefreshing: Bool
-    let isUpdatingProjection: Bool
+    let showsProjectionLoadingState: Bool
     let items: [MinecraftContentItem]
     let searchPrompt: String
     let chooseFolderAction: () -> Void
@@ -58,7 +58,7 @@ struct ItemListColumnView<MenuContent: View>: View {
                 }
                 .listStyle(.inset)
                 .overlay {
-                    if isUpdatingProjection && items.isEmpty {
+                    if showsProjectionLoadingState && items.isEmpty {
                         ItemListLoadingOverlay()
                     }
                 }
@@ -73,7 +73,7 @@ struct ItemListColumnView<MenuContent: View>: View {
                     subtitle: subtitle,
                     showsSubtitle: showsSubtitle,
                     isRefreshing: isRefreshing,
-                    isUpdatingProjection: isUpdatingProjection
+                    showsProjectionLoadingState: showsProjectionLoadingState
                 )
             }
         }
@@ -106,7 +106,7 @@ private struct ItemListHeaderView: View {
     let subtitle: String
     let showsSubtitle: Bool
     let isRefreshing: Bool
-    let isUpdatingProjection: Bool
+    let showsProjectionLoadingState: Bool
 
     var body: some View {
         VStack(alignment: .leading, spacing: 8) {
@@ -121,13 +121,13 @@ private struct ItemListHeaderView: View {
                     .font(.title2.weight(.semibold))
                     .lineLimit(2)
 
-                if isRefreshing || isUpdatingProjection {
+                if isRefreshing || showsProjectionLoadingState {
                     ProgressView()
                         .appActivityIndicatorStyle(.small)
                 }
             }
 
-            if showsSubtitle || isUpdatingProjection {
+            if showsSubtitle || showsProjectionLoadingState {
                 Text(displaySubtitle)
                     .appTextStyle(.supporting)
             }
@@ -140,7 +140,7 @@ private struct ItemListHeaderView: View {
     }
 
     private var displaySubtitle: String {
-        if isUpdatingProjection {
+        if showsProjectionLoadingState {
             return "Loading items..."
         }
 

World Manager for Minecraft/UI/Preview/PreviewFixtures.swift

@@ -323,7 +323,7 @@ struct ItemListColumnPreviewContainer: View {
                 subtitle: "5 items in Kid iPad Imports",
                 showsSubtitle: false,
                 isRefreshing: false,
-                isUpdatingProjection: false,
+                showsProjectionLoadingState: false,
                 items: PreviewFixtures.primarySource.displayItems,
                 searchPrompt: "Search Worlds",
                 chooseFolderAction: {},

World Manager for Minecraft/UI/Root/ContentView.swift

@@ -20,6 +20,7 @@ struct ContentView: View {
     @State private var isShowingDeviceSourceSheet = false
     @State private var sortMode: ItemSortMode = .name
     @State private var directoryPreviewContents: [DirectoryEntry] = []
+    @State private var showsProjectionLoadingState = false
     @State private var itemListProjection = ItemCollectionProjection.placeholder(
         for: ItemCollectionProjectionRequest(
             selection: nil,
@@ -33,6 +34,7 @@ struct ContentView: View {
     private let deviceSourceFactory: ConnectedDeviceSourceFactory
     private let itemActionService: ContentItemActionService
     private let directoryPreviewLimit = 12
+    private let projectionLoadingDelay: Duration = .milliseconds(150)
 
     init() {
         let dependencies = ContentViewDependencies.makeDefault()
@@ -53,15 +55,25 @@ struct ContentView: View {
             sortMode: sortMode,
             source: resolvedCurrentSource
         )
+        let fastPathProjection = fastProjection(for: currentProjectionRequest, previousRequest: itemListProjection.request)
         let reusesCurrentProjectedItems =
             itemListProjection.request.selection == currentProjectionRequest.selection &&
             itemListProjection.request.source?.id == currentProjectionRequest.source?.id
-        let isUpdatingItemListProjection = itemListProjection.request != currentProjectionRequest
+        let resolvedItemListProjection = if let fastPathProjection {
-        let resolvedItemListProjection = itemListProjection.request == currentProjectionRequest
+            fastPathProjection
-            ? itemListProjection
+        } else if itemListProjection.request == currentProjectionRequest {
-            : ItemCollectionProjection.placeholder(for: currentProjectionRequest)
+            itemListProjection
+        } else {
+            ItemCollectionProjection.placeholder(for: currentProjectionRequest)
+        }
         let resolvedCurrentSelectedItem = currentSelectedItem(in: resolvedCurrentSource)
-        let resolvedDisplayedItems = reusesCurrentProjectedItems ? itemListProjection.items : []
+        let resolvedDisplayedItems: [MinecraftContentItem] = if let fastPathProjection {
+            fastPathProjection.items
+        } else if reusesCurrentProjectedItems {
+            itemListProjection.items
+        } else {
+            []
+        }
 
         NavigationSplitView(columnVisibility: $columnVisibility) {
             SourcesSidebarView(
@@ -94,9 +106,9 @@ struct ContentView: View {
                 showsSourceName: !isSidebarVisible,
                 title: resolvedItemListProjection.title,
                 subtitle: resolvedItemListProjection.subtitle,
-                showsSubtitle: isSearching || isUpdatingItemListProjection,
+                showsSubtitle: isSearching || showsProjectionLoadingState,
                 isRefreshing: resolvedCurrentSource?.isScanning == true,
-                isUpdatingProjection: isUpdatingItemListProjection,
+                showsProjectionLoadingState: showsProjectionLoadingState,
                 items: resolvedDisplayedItems,
                 searchPrompt: resolvedItemListProjection.searchPrompt,
                 chooseFolderAction: pickFolder,
@@ -180,14 +192,41 @@ struct ContentView: View {
         }
         .task(id: currentProjectionRequest) {
             let request = currentProjectionRequest
+            if let fastPathProjection = fastProjection(for: request, previousRequest: itemListProjection.request) {
+                showsProjectionLoadingState = false
+                itemListProjection = fastPathProjection
+                return
+            }
+
             let projection = await Task.detached(priority: .userInitiated) {
                 ItemCollectionProjector.makeProjection(for: request)
             }.value
             guard !Task.isCancelled else {
                 return
             }
+            showsProjectionLoadingState = false
             itemListProjection = projection
         }
+        .task(id: currentProjectionRequest) {
+            showsProjectionLoadingState = false
+
+            guard itemListProjection.request != currentProjectionRequest else {
+                return
+            }
+
+            guard fastProjection(for: currentProjectionRequest, previousRequest: itemListProjection.request) == nil else {
+                return
+            }
+
+            try? await Task.sleep(for: projectionLoadingDelay)
+            guard !Task.isCancelled else {
+                return
+            }
+
+            if itemListProjection.request != currentProjectionRequest {
+                showsProjectionLoadingState = true
+            }
+        }
         .task(id: resolvedCurrentSelectedItem?.id) {
             await refreshDirectoryPreviewContents()
         }
@@ -224,10 +263,9 @@ struct ContentView: View {
             return item
         }
 
-        for source in library.visibleSources {
+        if let sourceID = library.sourceID(forItemID: selectedItemID),
-            if let item = source.items.first(where: { $0.id == selectedItemID }) {
+           let source = library.source(withID: sourceID) {
-                return item
+            return source.items.first(where: { $0.id == selectedItemID })
-            }
         }
 
         return nil
@@ -558,18 +596,17 @@ struct ContentView: View {
         }
 
         if let selectedItemID {
-            let itemStillExists = library.visibleSources
+            if !library.containsItem(withID: selectedItemID) {
-                .flatMap(\.items)
-                .contains(where: { $0.id == selectedItemID })
-
-            if !itemStillExists {
                 self.selectedItemID = nil
             }
         }
     }
 
     private func areFileActionsEnabled(for item: MinecraftContentItem) -> Bool {
-        guard let source = library.visibleSources.first(where: { $0.items.contains(where: { $0.id == item.id }) }) else {
+        guard
+            let sourceID = library.sourceID(forItemID: item.id),
+            let source = library.source(withID: sourceID)
+        else {
             return false
         }
 
@@ -577,9 +614,28 @@ struct ContentView: View {
     }
 
     private func sourceForItem(_ item: MinecraftContentItem) -> MinecraftSource? {
-        library.visibleSources.first(where: { source in
+        guard let sourceID = library.sourceID(forItemID: item.id) else {
-            source.items.contains(where: { $0.id == item.id })
+            return nil
-        })
+        }
+
+        return library.source(withID: sourceID)
+    }
+
+    private func fastProjection(
+        for request: ItemCollectionProjectionRequest,
+        previousRequest: ItemCollectionProjectionRequest
+    ) -> ItemCollectionProjection? {
+        guard
+            let sourceID = request.source?.id,
+            sourceID == previousRequest.source?.id,
+            request.searchText == previousRequest.searchText,
+            request.sortMode == previousRequest.sortMode,
+            request.selection != previousRequest.selection
+        else {
+            return nil
+        }
+
+        return ItemCollectionProjector.makeProjection(for: request)
     }
 
     private func saveItem(_ item: MinecraftContentItem) {