How do I set a minimum size for a window and make it use the specified size and position when launching?

Question

I am making a MacOS app with the default SwiftUI Application template. How can I set the minimum size of the window to (800, 500)? Also if I close the window, and reopen, it reopens as the size and position from when it last closed. How do I make it not remember the window position and size from when it last closed? I am using Xcode 11.2.1 and MacOS Catalina. How can I do these?

Answer 1

If you created project from template for macOS SwiftUI based, then all changes you need to do is in AppDelegate.swift.

The size of window is content-defined, so you need to specify root content view frame, and to disallow window position saving you need to remove setFrameAutosaveName, as a result your AppDelegate should look like the following

@NSApplicationMain
class AppDelegate: NSObject, NSApplicationDelegate {

    var window: NSWindow!

    func applicationDidFinishLaunching(_ aNotification: Notification) {
        // Create the SwiftUI view that provides the window contents.
        let contentView = ContentView()
            .frame(minWidth: 800, maxWidth: .infinity, minHeight: 500, maxHeight: .infinity)

        // Create the window and set the content view. 
        window = NSWindow(
            contentRect: NSRect(x: 0, y: 0, width: 800, height: 500),
            styleMask: [.titled, .closable, .miniaturizable, .resizable, .fullSizeContentView],
            backing: .buffered, defer: false)
        window.center()
        window.contentView = NSHostingView(rootView: contentView)
        window.makeKeyAndOrderFront(nil)
    }
    ...

Update: for SwiftUI life-cycle approach is the same - set frame to content view in window scene, like

var body: some Scene {
    WindowGroup {
        ContentView()
            .frame(minWidth: 800, maxWidth: .infinity, minHeight: 500, maxHeight: .infinity)
    }
}