Show one settings section at a time

Packages/macOS/CmuxSettingsUI/Sources/CmuxSettingsUI/Scene/SettingsSectionSlot.swift

@@ -13,6 +13,10 @@ import SwiftUI
 @MainActor
 struct SettingsSectionSlot<Content: View>: View {
     let section: SettingsSectionID
+    /// Only the selected pane is part of the hierarchy. Keeping inactive
+    /// sections out avoids constructing all settings controls at window open
+    /// and gives the window true one-pane-at-a-time behavior.
+    let isActive: Bool
     let isMounted: Bool
     /// `false` renders nothing while unmounted, for sections that hide
     /// themselves entirely (Cloud before it is available).
@@ -23,12 +27,18 @@ struct SettingsSectionSlot<Content: View>: View {
     var body: some View {
         // The same spacing as the enclosing detail stack, so a section's
         // header and cards sit exactly where the flat stack put them.
-        VStack(alignment: .leading, spacing: 14) {
-            if isMounted {
-                content()
-                    .onAppear { onMountedAppear() }
-            } else if showsPlaceholder {
-                SettingsSectionPlaceholder(section: section)
+        Group {
+            if isActive {
+                VStack(alignment: .leading, spacing: 14) {
+                    if isMounted {
+                        content()
+                            .onAppear { onMountedAppear() }
+                    } else if showsPlaceholder {
+                        SettingsSectionPlaceholder(section: section)
+                    }
+                }
+            } else {
+                EmptyView()
             }
         }
         .id("section:\(section.rawValue)")

Packages/macOS/CmuxSettingsUI/Sources/CmuxSettingsUI/Scene/SettingsWindowScene+Sections.swift

@@ -167,6 +167,7 @@ extension SettingsWindowRoot {
     ) -> some View {
         SettingsSectionSlot(
             section: section,
+            isActive: section == selectedSection,
             isMounted: mountModel.isMounted(section),
             showsPlaceholder: section != .cloudMachines || isCloudSectionAvailable,
             onMountedAppear: { sectionContentDidAppear(section, proxy: proxy) },

Packages/macOS/CmuxSettingsUI/Sources/CmuxSettingsUI/Scene/SettingsWindowScene.swift

@@ -445,6 +445,7 @@ public struct SettingsWindowRoot: View {
                 .onReceive(NotificationCenter.default.publisher(for: Self.navigationRequestName)) { notification in
                     applyScrollNavigation(notification, proxy: proxy)
                 }
+                .navigationTitle(selectedSection.title)
             }
         }
     }

Sources/App/SettingsWindowFactory.swift

@@ -56,6 +56,10 @@ enum SettingsWindowFactory {
         // the defaults is what produced the #8015 hybrid chrome.
         window.styleMask = [.titled, .closable, .miniaturizable, .resizable, .fullSizeContentView]
         window.title = String(localized: "settings.title", defaultValue: "Settings")
+        // Settings panes are not document windows: HIG guidance keeps the
+        // minimize and zoom controls visible but unavailable.
+        window.standardWindowButton(.miniaturizeButton)?.isEnabled = false
+        window.standardWindowButton(.zoomButton)?.isEnabled = false
         // [flexible space, sidebar toggle, sidebar tracking separator] is the
         // exact item layout the SwiftUI-owned 0.64.17 window built for its
         // NavigationSplitView: the toggle sits at the sidebar's trailing edge