Scale file browser performance for large folders

.github/workflows/performance-tests.yml

@@ -0,0 +1,27 @@
+name: File Browser Performance Tests
+
+on:
+  push:
+  pull_request:
+    branches: [main]
+
+permissions:
+  contents: read
+
+jobs:
+  performance-tests:
+    runs-on: macos-26
+    timeout-minutes: 10
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          persist-credentials: false
+
+      - name: Select Xcode
+        run: sudo xcode-select -s /Applications/Xcode_26.2.app || sudo xcode-select -s /Applications/Xcode.app
+
+      - name: Run file browser tests
+        run: |
+          chmod +x run-tests.sh run-ui-tests.sh
+          ./run-tests.sh
+          ./run-ui-tests.sh

Sources/mindle/ContentView.swift

@@ -22,7 +22,12 @@ struct ContentView: View {
                     }
                     HSplitView {
                         if store.showFileBrowser {
-                            FileBrowserSidebar()
+                            FileBrowserSidebar(
+                                browser: store.fileBrowser,
+                                theme: store.theme,
+                                onRefresh: store.refreshFileTree,
+                                onOpen: store.open
+                            )
                                 .frame(minWidth: 200, idealWidth: 260, maxWidth: 400)
                         }
                         ReaderPane()
@@ -49,7 +54,7 @@ struct ContentView: View {
                     withAnimation(.easeInOut(duration: 0.18)) {
                         store.showFileBrowser.toggle()
                     }
-                    if store.showFileBrowser && store.fileTree == nil {
+                    if store.showFileBrowser && store.fileBrowser.tree == nil {
                         store.refreshFileTree()
                     }
                 } label: {
@@ -146,6 +151,9 @@ struct ContentView: View {
             }
             return false
         }
+        .onDisappear {
+            store.fileBrowser.cancelAll()
+        }
     }
 
     private func themeIcon(_ t: ReaderTheme) -> String {
@@ -1284,140 +1292,6 @@ struct AnnotationMessageRow: View {
     }()
 }
 
-// MARK: - File browser sidebar
-
-struct FileBrowserSidebar: View {
-    @EnvironmentObject var store: DocumentStore
-
-    var body: some View {
-        let c = store.theme.colors
-        VStack(alignment: .leading, spacing: 0) {
-            HStack(spacing: 8) {
-                Image(systemName: "folder")
-                    .foregroundStyle(c.accent)
-                Text("Files")
-                    .font(.system(size: 13, weight: .semibold, design: .serif))
-                    .foregroundStyle(c.text)
-                Spacer()
-                Button {
-                    store.refreshFileTree()
-                } label: {
-                    Image(systemName: "arrow.clockwise")
-                        .font(.system(size: 11))
-                }
-                .buttonStyle(.plain)
-                .foregroundStyle(c.muted)
-                .help("Refresh file list")
-            }
-            .padding(.horizontal, 16)
-            .padding(.vertical, 12)
-
-            Rectangle().fill(c.rule.opacity(0.4)).frame(height: 0.5)
-
-            if let tree = store.fileTree, let children = tree.children, !children.isEmpty {
-                ScrollView {
-                    // Non-lazy VStack so the tree's content size stays constant
-                    // when other window state changes (e.g. fileURL flipping
-                    // isCurrent on a row, or the TabBar appearing/disappearing
-                    // as tabs.count crosses the 2-to-1 boundary). LazyVStack
-                    // re-measured rows on those events and could nudge the
-                    // scroll position, making the active row appear to shift
-                    // (#36). The directories Mindle browses are typically
-                    // small enough that eager realization is fine.
-                    VStack(alignment: .leading, spacing: 0) {
-                        ForEach(children) { child in
-                            FileTreeRow(node: child, depth: 0)
-                        }
-                    }
-                    .padding(.vertical, 6)
-                }
-            } else {
-                VStack(spacing: 8) {
-                    Image(systemName: "tray")
-                        .font(.system(size: 28, weight: .ultraLight))
-                        .foregroundStyle(c.muted.opacity(0.7))
-                    Text("No markdown files\nin this directory.")
-                        .multilineTextAlignment(.center)
-                        .font(.system(size: 12, design: .serif).italic())
-                        .foregroundStyle(c.muted)
-                        .padding(.horizontal, 24)
-                }
-                .frame(maxWidth: .infinity, maxHeight: .infinity)
-            }
-        }
-        .background(c.sidebar)
-    }
-}
-
-struct FileTreeRow: View {
-    let node: FileNode
-    let depth: Int
-    @EnvironmentObject var store: DocumentStore
-    @State private var isExpanded: Bool = true
-
-    var body: some View {
-        let c = store.theme.colors
-        if node.isDirectory {
-            Button {
-                withAnimation(.easeInOut(duration: 0.12)) { isExpanded.toggle() }
-            } label: {
-                HStack(spacing: 6) {
-                    Image(systemName: isExpanded ? "chevron.down" : "chevron.right")
-                        .font(.system(size: 9, weight: .semibold))
-                        .foregroundStyle(c.muted)
-                        .frame(width: 10)
-                    Image(systemName: "folder")
-                        .font(.system(size: 11))
-                        .foregroundStyle(c.muted)
-                    Text(node.name)
-                        .font(.system(size: 12, weight: .medium, design: .serif))
-                        .foregroundStyle(c.text)
-                        .lineLimit(1)
-                        .truncationMode(.middle)
-                    Spacer(minLength: 0)
-                }
-                .padding(.leading, CGFloat(depth) * 14 + 8)
-                .padding(.trailing, 10)
-                .padding(.vertical, 4)
-                .frame(maxWidth: .infinity, alignment: .leading)
-                .contentShape(Rectangle())
-            }
-            .buttonStyle(.plain)
-
-            if isExpanded {
-                ForEach(node.children ?? []) { child in
-                    FileTreeRow(node: child, depth: depth + 1)
-                }
-            }
-        } else {
-            let isCurrent = store.fileURL?.standardizedFileURL == node.url.standardizedFileURL
-            Button {
-                store.open(url: node.url)
-            } label: {
-                HStack(spacing: 6) {
-                    Spacer().frame(width: 10)
-                    Image(systemName: "doc.text")
-                        .font(.system(size: 11))
-                        .foregroundStyle(isCurrent ? c.accent : c.muted)
-                    Text(node.name)
-                        .font(.system(size: 12, design: .serif))
-                        .foregroundStyle(c.text)
-                        .lineLimit(1)
-                        .truncationMode(.middle)
-                    Spacer(minLength: 0)
-                }
-                .padding(.leading, CGFloat(depth) * 14 + 8)
-                .padding(.trailing, 10)
-                .padding(.vertical, 4)
-                .frame(maxWidth: .infinity, alignment: .leading)
-                .background(isCurrent ? c.accent.opacity(0.14) : Color.clear)
-                .contentShape(Rectangle())
-            }
-            .buttonStyle(.plain)
-        }
-    }
-}
-
 // MARK: - Tab bar
 
 struct TabBar: View {

Sources/mindle/DocumentStore.swift

@@ -169,14 +169,6 @@ enum AnnotationStatus: String, Codable {
     case open, resolved, wontfix
 }
 
-struct FileNode: Identifiable, Equatable {
-    var id: URL { url }
-    let url: URL
-    let name: String
-    let isDirectory: Bool
-    let children: [FileNode]?   // nil = leaf file; non-nil = directory
-}
-
 /// One open document inside a window. Active-tab state still lives in
 /// the window-scoped @Published vars (`fileURL`, `rawText`, `annotations`,
 /// `lastSyncedText`) so all existing features keep working untouched;
@@ -300,7 +292,7 @@ final class DocumentStore: ObservableObject {
     }
     @Published var showAnnotations: Bool = false
     @Published var showFileBrowser: Bool = false
-    @Published var fileTree: FileNode? = nil
+    let fileBrowser = FileBrowserState()
 
     // Tabs (per-window). Empty when no document is open; otherwise the active
     // tab's state mirrors `fileURL` / `rawText` / `annotations` above.
@@ -522,8 +514,12 @@ final class DocumentStore: ObservableObject {
             // the markdown pipeline (markdown-it, search, highlight, diff)
             // doesn't try to do anything with the binary PDF bytes.
             let kind = DocumentKind.kind(for: url)
-            let text: String = (kind == .pdf) ? "" : try String(contentsOf: url, encoding: .utf8)
-            finishOpen(url: url, text: text, kind: kind, sourceURL: nil, remoteTarget: nil)
+            let text: String = try PerformanceTrace.measure("LocalFileRead") {
+                (kind == .pdf) ? "" : try String(contentsOf: url, encoding: .utf8)
+            }
+            PerformanceTrace.measure("FileOpenApply") {
+                finishOpen(url: url, text: text, kind: kind, sourceURL: nil, remoteTarget: nil)
+            }
         } catch {
             NSSound.beep()
         }
@@ -537,8 +533,8 @@ final class DocumentStore: ObservableObject {
         // Re-root the file tree only when the new file is outside the current scope.
         // Clicking a file inside a subfolder of the current root must preserve rooting.
         let shouldRebuildTree: Bool
-        if let root = fileTree?.url {
-            shouldRebuildTree = !Self.isDescendant(url: url, of: root)
+        if let root = fileBrowser.rootURL {
+            shouldRebuildTree = !FileTreeBuilder.isDescendant(url, of: root)
         } else {
             shouldRebuildTree = true
         }
@@ -571,7 +567,10 @@ final class DocumentStore: ObservableObject {
         // Capture the sidecar-loaded annotations into the tab snapshot.
         snapshotActiveTab()
 
-        if shouldRebuildTree { refreshFileTree() }
+        if shouldRebuildTree {
+            fileBrowser.setRoot(url.deletingLastPathComponent())
+        }
+        syncFileBrowserSelection(for: url)
         if url.isFileURL && remoteTarget == nil {
             NSDocumentController.shared.noteNewRecentDocumentURL(url)
         }
@@ -860,6 +859,7 @@ final class DocumentStore: ObservableObject {
         lastSyncedText = placeholder
         annotations = []
         collaborators = [:]
+        syncFileBrowserSelection(for: url)
         closeSearch()
         focusedAnnotation = nil
         editingAnnotationID = nil
@@ -924,6 +924,7 @@ final class DocumentStore: ObservableObject {
         lastSyncedText = raw
         annotations = []
         collaborators = [:]
+        syncFileBrowserSelection(for: url)
         closeSearch()
         focusedAnnotation = nil
         editingAnnotationID = nil
@@ -1098,6 +1099,7 @@ final class DocumentStore: ObservableObject {
             // Last tab closed — back to empty state.
             activeTabID = nil
             fileURL = nil
+            syncFileBrowserSelection(for: nil)
             activeRemoteTarget = nil
             rawText = ""
             lastSyncedText = ""
@@ -1124,6 +1126,7 @@ final class DocumentStore: ObservableObject {
 
     private func loadTabState(_ tab: DocumentTab) {
         fileURL = tab.fileURL
+        syncFileBrowserSelection(for: tab.fileURL)
         self.activeRemoteTarget = tab.sourceURL.flatMap { SSHTarget(sourceURL: $0) }
         rawText = tab.rawText
         lastSyncedText = tab.lastSyncedText
@@ -1172,48 +1175,29 @@ final class DocumentStore: ObservableObject {
 
     // MARK: - File browser
 
-    static let browsableExtensions: Set<String> = ["md", "markdown", "mdown", "mkd", "txt", "pdf"]
-
     func refreshFileTree() {
-        guard let url = fileURL else { fileTree = nil; return }
-        fileTree = Self.buildTree(at: url.deletingLastPathComponent())
-    }
-
-    private static func isDescendant(url: URL, of ancestor: URL) -> Bool {
-        let aPath = ancestor.standardizedFileURL.path
-        let uPath = url.standardizedFileURL.path
-        let prefix = aPath.hasSuffix("/") ? aPath : aPath + "/"
-        return uPath.hasPrefix(prefix)
-    }
-
-    private static func buildTree(at dir: URL) -> FileNode? {
-        let fm = FileManager.default
-        guard let entries = try? fm.contentsOfDirectory(
-            at: dir,
-            includingPropertiesForKeys: [.isDirectoryKey],
-            options: [.skipsHiddenFiles]
-        ) else {
-            return FileNode(url: dir, name: dir.lastPathComponent, isDirectory: true, children: [])
+        guard let url = fileURL, url.isFileURL else {
+            fileBrowser.setRoot(nil)
+            return
         }
-
-        var children: [FileNode] = []
-        for entry in entries {
-            let isDir = (try? entry.resourceValues(forKeys: [.isDirectoryKey]).isDirectory) ?? false
-            if isDir {
-                if let sub = buildTree(at: entry), !(sub.children ?? []).isEmpty {
-                    children.append(sub)
-                }
-            } else if browsableExtensions.contains(entry.pathExtension.lowercased()) {
-                children.append(FileNode(url: entry, name: entry.lastPathComponent, isDirectory: false, children: nil))
-            }
+        let root = fileBrowser.rootURL
+        if let root, FileTreeBuilder.isDescendant(url, of: root) {
+            fileBrowser.refresh()
+        } else {
+            fileBrowser.setRoot(url.deletingLastPathComponent())
         }
+        syncFileBrowserSelection(for: url)
+    }
 
-        children.sort { a, b in
-            if a.isDirectory != b.isDirectory { return a.isDirectory }
-            return a.name.localizedCaseInsensitiveCompare(b.name) == .orderedAscending
+    private func syncFileBrowserSelection(for url: URL?) {
+        guard let url,
+              url.isFileURL,
+              let root = fileBrowser.rootURL,
+              FileTreeBuilder.isDescendant(url, of: root) else {
+            fileBrowser.setSelectedURL(nil)
+            return
         }
-
-        return FileNode(url: dir, name: dir.lastPathComponent, isDirectory: true, children: children)
+        fileBrowser.setSelectedURL(url)
     }
 
     func toggleTheme() {