Modify AppDelegate to present Settings window when needed

Tartelet/Sources/AppDelegate.swift

@@ -16,6 +16,18 @@ final class AppDelegate: NSObject, NSApplicationDelegate {
         if Composers.settingsStore.startVirtualMachinesOnLaunch {
             Composers.fleet.start(numberOfMachines: Composers.settingsStore.numberOfVirtualMachines)
         }
+
+        // If Tartelet is launched as a login item, we can keep the window hidden
+        if launchedAsLogInItem == false {
+            openSettingsWindow()
+        }
+    }
+
+    // This delegate method let's you perform an action whenever the Finder reactivates an already
+    // running application when the app is double-clicked again or clicked on in the dock.
+    func applicationShouldHandleReopen(_ sender: NSApplication, hasVisibleWindows flag: Bool) -> Bool {
+        openSettingsWindow()
+        return true
     }
 
     func applicationWillTerminate(_ notification: Notification) {
@@ -35,4 +47,59 @@ private extension AppDelegate {
             }
         }
     }
+
+    private var launchedAsLogInItem: Bool {
+        // source: https://stackoverflow.com/a/19890943/4118208
+        guard let event = NSAppleEventManager.shared().currentAppleEvent else {
+            return false
+        }
+        return
+            event.eventID == kAEOpenApplication &&
+            event.paramDescriptor(forKeyword: keyAEPropData)?.enumCodeValue == keyAELaunchedAsLogInItem
+    }
+
+    /// Opens Tartelet's Settings window
+    ///
+    /// To open the Settings/Preferences window programmatically in the past, we'd use:
+    ///
+    /// ```swift
+    /// NSApp.sendAction(Selector(("showSettingsWindow:")), to: nil, from: nil)
+    /// ```
+    ///
+    /// Unfortunately, Apple removed the ability to do that, so we have to do the slightly
+    /// hacky alternative of scanning through the app's menu items and activating the
+    /// "Settings…" menu item directly. Not ideal, but it works.
+    func openSettingsWindow() {
+        // Works around an annoyance where the app always comes to the foreground when
+        // being previewed in Xcode's SwiftUI Canvas.
+        guard
+            ProcessInfo.processInfo.environment["XCODE_RUNNING_FOR_PREVIEWS"] != "1"
+        else {
+            return
+        }
+
+        guard
+            let menu = NSApplication.shared.menu,
+            let sensoriumMenu = menu.items.first,
+            let sensoriumMenuSubmenu = sensoriumMenu.submenu,
+            let settingsMenuItem = sensoriumMenuSubmenu.items[safe: 2],
+            let settingsMenuItemAction = settingsMenuItem.action
+        else {
+            return
+        }
+
+        NSApp.sendAction(
+            settingsMenuItemAction,
+            to: settingsMenuItem.target,
+            from: settingsMenuItem
+        )
+        NSApp.activate(ignoringOtherApps: true)
+    }
+}
+
+extension Collection {
+    /// Checks first if an index exists in an array, and returns `nil` if it does not exist.
+    subscript(safe index: Index) -> Element? {
+        indices.contains(index) ? self[index] : nil
+    }
 }