feat(macOS): Separate multi-window and instance

[PartyDonut]

Pull Request Description

Add support for multiple window/instances on macOS

[Copilot]

Pull request overview

This pull request adds support for creating multiple instances of the application on macOS, alongside the existing multi-window functionality. The implementation distinguishes between opening a new window within the current instance (openNewWindow) and launching an entirely new application instance (newInstance).

• Adds a new newInstance() method to the ApplicationMenu Pigeon API that spawns a new application process
• Implements platform-specific logic for macOS, Windows, and Linux to launch new instances
• Adds a "New Instance" menu item to the macOS dock menu

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
pigeons/application_menu.dart	Adds new newInstance() method to the ApplicationMenu API definition
macos/Runner/ApplicationMenu.g.swift	Auto-generated Pigeon code for the new Swift-side API (v26.1.0)
macos/Runner/DirectoryBookmark.g.swift	Updated to Pigeon v26.1.0 (version bump only)
macos/Runner/AppDelegate.swift	Adds "New Instance" dock menu item and handler that calls the new API
lib/logic/application_menu.dart	Implements newInstance() with platform-specific process spawning logic
lib/src/application_menu.g.dart	Auto-generated Pigeon code for the Dart-side API (v26.1.0)
lib/src/*.g.dart	Auto-generated files updated to Pigeon v26.1.0
android/app/src/main/kotlin/**/*.g.kt	Auto-generated Kotlin files updated to Pigeon v26.1.0 with API improvements

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[Copilot]

The new newInstance() method lacks documentation. Consider adding a doc comment to explain what it does and how it differs from openNewWindow(). This will help API consumers understand when to use each method.

Suggested change

	void openNewWindow();
	void openNewWindow();
	/// Creates a new instance of the application.
	///
	/// Unlike [openNewWindow], which opens a new window in the current application
	/// process, [newInstance] launches a completely new application process.
	/// Use this when a full, separate instance is required rather than just a new window.

[Copilot]

The Windows implementation doesn't use ProcessStartMode.detached unlike Linux. This may cause the spawned process to be tied to the parent process lifecycle. Consider using mode: ProcessStartMode.detached for consistency with the Linux implementation and to ensure the new instance runs independently.

Suggested change

	await Process.start(Platform.resolvedExecutable, []);
	await Process.start(Platform.resolvedExecutable, [], mode: ProcessStartMode.detached);

[Copilot]

Both dock menu items have the same keyboard shortcut 'n'. This will cause a conflict where only one of the menu items can be triggered with the shortcut. Consider using a different shortcut for the "New Instance" action, such as 'N' (uppercase) or another key combination.

Suggested change

	keyEquivalent: "n"
	keyEquivalent: "N"

[Copilot]

The spawned process is not being awaited or its result handled. If Process.start fails (e.g., due to permissions or invalid path), the error will be silently ignored. Consider handling potential errors or at least logging failures. Additionally, the process handle is not stored, which may lead to resource leaks on some platforms.

Suggested change

	if (Platform.isMacOS) {
	await Process.start('open', ['-n', '-a', Platform.resolvedExecutable]);
	} else if (Platform.isWindows) {
	await Process.start(Platform.resolvedExecutable, []);
	} else if (Platform.isLinux) {
	await Process.start(Platform.resolvedExecutable, [], mode: ProcessStartMode.detached);
	try {
	if (Platform.isMacOS) {
	final process = await Process.start('open', ['-n', '-a', Platform.resolvedExecutable]);
	// Close the process handle to avoid resource leaks
	process.stdin.close();
	process.stdout.drain();
	process.stderr.drain();
	process.kill();
	} else if (Platform.isWindows) {
	final process = await Process.start(Platform.resolvedExecutable, []);
	// Close the process handle to avoid resource leaks
	process.stdin.close();
	process.stdout.drain();
	process.stderr.drain();
	process.kill();
	} else if (Platform.isLinux) {
	await Process.start(Platform.resolvedExecutable, [], mode: ProcessStartMode.detached);
	}
	} catch (e) {
	print('Failed to start new instance: $e');

[Copilot]

Consider adding error handling for the completion callback. Currently, all results (success or failure) are treated the same way with a generic print statement. It would be more robust to handle potential errors from the Pigeon API call.

Suggested change

	self.appMenuApi?.openNewWindow(completion: {_ in print("New window opened")})
	}
	@objc func handleNewInstanceAction(_ sender: NSMenuItem) {
	self.appMenuApi?.newInstance(completion: {_ in print("New instance opened")})
	self.appMenuApi?.openNewWindow(completion: { error in
	if let error = error {
	print("Failed to open new window: \(error)")
	} else {
	print("New window opened")
	}
	})
	}
	@objc func handleNewInstanceAction(_ sender: NSMenuItem) {
	self.appMenuApi?.newInstance(completion: { error in
	if let error = error {
	print("Failed to open new instance: \(error)")
	} else {
	print("New instance opened")
	}
	})