Add a flag-gated AppKit NSTableView core for the workspace sidebar

Packages/macOS/CmuxSettings/Sources/CmuxSettings/Keys/BetaFeaturesCatalogSection.swift

@@ -56,6 +56,16 @@ public struct BetaFeaturesCatalogSection: SettingCatalogSection {
         userDefaultsKey: "sidebarWorkspaceTodosChecklistStyle"
     )
 
+    /// AppKit sidebar list: renders the workspace sidebar's scrollable list
+    /// with a native NSTableView (measured-once row heights, explicit
+    /// diffing) instead of the SwiftUI LazyVStack scroll core. Defaults off;
+    /// while off, the existing SwiftUI list path is unchanged.
+    public let appKitSidebarList = DefaultsKey<Bool>(
+        id: "sidebar.beta.appKitList.enabled",
+        defaultValue: false,
+        userDefaultsKey: "sidebar.beta.appKitList.enabled"
+    )
+
     /// Remote tmux: mirror a remote host's tmux sessions in the cmux sidebar
     /// over `ssh … tmux -CC` (iTerm2-style control mode). Sessions appear as
     /// sidebar workspaces, tmux windows as tabs, and tmux panes as splits;

Packages/macOS/CmuxSettingsUI/Sources/CmuxSettingsUI/Sections/BetaFeaturesSection.swift

@@ -11,6 +11,7 @@ public struct BetaFeaturesSection: View {
     @State private var dock: DefaultsValueModel<Bool>
     @State private var extensions: DefaultsValueModel<Bool>
     @State private var customSidebars: DefaultsValueModel<Bool>
+    @State private var appKitSidebarList: DefaultsValueModel<Bool>
     @State private var remoteTmux: DefaultsValueModel<Bool>
     @State private var workspaceTodosChecklistStyle: DefaultsValueModel<WorkspaceTodoChecklistStyle>
 
@@ -19,6 +20,7 @@ public struct BetaFeaturesSection: View {
         _dock = State(initialValue: DefaultsValueModel(store: defaultsStore, key: catalog.betaFeatures.rightSidebarDock))
         _extensions = State(initialValue: DefaultsValueModel(store: defaultsStore, key: catalog.betaFeatures.extensions))
         _customSidebars = State(initialValue: DefaultsValueModel(store: defaultsStore, key: catalog.betaFeatures.customSidebars))
+        _appKitSidebarList = State(initialValue: DefaultsValueModel(store: defaultsStore, key: catalog.betaFeatures.appKitSidebarList))
         _remoteTmux = State(initialValue: DefaultsValueModel(store: defaultsStore, key: catalog.betaFeatures.remoteTmux))
         _workspaceTodosChecklistStyle = State(initialValue: DefaultsValueModel(store: defaultsStore, key: catalog.betaFeatures.workspaceTodosChecklistStyle))
     }
@@ -39,6 +41,8 @@ public struct BetaFeaturesSection: View {
                 SettingsCardDivider()
                 customSidebarsRow
                 SettingsCardDivider()
+                appKitSidebarListRow
+                SettingsCardDivider()
                 remoteTmuxRow
                 SettingsCardDivider()
                 workspaceTodosChecklistStyleRow
@@ -53,6 +57,7 @@ public struct BetaFeaturesSection: View {
             dock,
             extensions,
             customSidebars,
+            appKitSidebarList,
             remoteTmux,
             workspaceTodosChecklistStyle,
         ]
@@ -151,6 +156,23 @@ public struct BetaFeaturesSection: View {
         }
     }
 
+    @ViewBuilder
+    private var appKitSidebarListRow: some View {
+        SettingsCardRow(
+            configurationReview: .settingsOnly,
+            searchAnchorID: "setting:betaFeatures:appKitSidebarList",
+            String(localized: "settings.betaFeatures.appKitSidebarList", defaultValue: "AppKit Sidebar List"),
+            subtitle: appKitSidebarList.current
+                ? String(localized: "settings.betaFeatures.appKitSidebarList.subtitleOn", defaultValue: "Renders the workspace list with a native AppKit table for smoother scrolling with many workspaces.")
+                : String(localized: "settings.betaFeatures.appKitSidebarList.subtitleOff", defaultValue: "Uses the existing SwiftUI workspace list until you enable the native table here.")
+        ) {
+            Toggle("", isOn: Binding(get: { appKitSidebarList.current }, set: { appKitSidebarList.set($0) }))
+                .labelsHidden()
+                .controlSize(.small)
+                .accessibilityIdentifier("SettingsBetaAppKitSidebarListToggle")
+        }
+    }
+
     @ViewBuilder
     private var remoteTmuxRow: some View {
         SettingsCardRow(

Resources/Localizable.xcstrings

@@ -153871,6 +153871,57 @@
         }
       }
     },
+    "settings.betaFeatures.appKitSidebarList": {
+      "extractionState": "manual",
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "AppKit Sidebar List"
+          }
+        },
+        "ja": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "AppKit サイドバーリスト"
+          }
+        }
+      }
+    },
+    "settings.betaFeatures.appKitSidebarList.subtitleOff": {
+      "extractionState": "manual",
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Uses the existing SwiftUI workspace list until you enable the native table here."
+          }
+        },
+        "ja": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "ここで有効にするまで、既存の SwiftUI ワークスペースリストを使用します。"
+          }
+        }
+      }
+    },
+    "settings.betaFeatures.appKitSidebarList.subtitleOn": {
+      "extractionState": "manual",
+      "localizations": {
+        "en": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Renders the workspace list with a native AppKit table for smoother scrolling with many workspaces."
+          }
+        },
+        "ja": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "ワークスペースリストをネイティブの AppKit テーブルで描画し、多数のワークスペースでもスクロールを滑らかにします。"
+          }
+        }
+      }
+    },
     "settings.betaFeatures.customSidebars": {
       "extractionState": "manual",
       "localizations": {