How do I create and print an offscreen SwiftUI view on Mac not iPhone

Question

For over a week I have been trying to solve a printing issue in a macOS app I am writing using Swift and SwiftUI.

I need to print a view, which I have done by making it the main window but that does not work for the user. The data can come from a file or directly from user input so could be from 1 to 100 data sets.

Because I am printing the main window the application is unusable during the print process which is not acceptable.

The ideal solution would be to create the view off-screen then print the view. That way the user never sees it other than what comes out of the printer!

I have tried to find out how to print a view that is not the main window - no success, tried creating a second window managed to create the window but not print it!

No point in posting code as no idea which of the several ways I have tried could work, not even sure at this point if what I am trying to do is possible!

Please note this on Mac, not iPhone or iPad!

Answer 1

This worked for me, borrowed from the link in the comment from @Willeke . It involves converting to a bit map for printing.

let printInfo = NSPrintInfo()

let view = ContentView()
let contentRect = NSRect(x: 0, y: 0, width: 1080, height: 720) // these values will vary

let viewToPrint = NSHostingView(rootView: view)
viewToPrint.frame = contentRect

let bitMap = viewToPrint.bitmapImageRepForCachingDisplay(in: contentRect)!
viewToPrint.cacheDisplay(in: contentRect, to: bitMap)

let image = NSImage(size: bitMap.size)
image.addRepresentation(bitMap)

let imageView = NSImageView(frame: contentRect)
imageView.image = image

let printOperation = NSPrintOperation(view: imageView, printInfo: self.printInfo)
printOperation.showsPrintPanel = true
printOperation.showsProgressPanel = true
printOperation.run()