NSView.knowsPageRange(_:) called twice when showing print panel

Question

Created 3d

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Participants 2

When creating a default macOS document-based Xcode project and using the code below (and wiring the File menu's Print item to printDocument: instead of the default print:, which does nothing), opening the print panel causes PrintView.knowsPageRange(_:) to be called twice.

Is this a bug? My app populates PrintView dynamically, and for large documents it can be quite inefficient to populate it once, only for the contents to be immediately discarded and populated again.

A workaround that came to my mind would be to check if the print options have changed, though I'm not sure if it's a reliable indicator that the print preview is effectively the same.

I created FB17018494.

 class Document: NSDocument {
 
    override func makeWindowControllers() {
        addWindowController(NSStoryboard(name: NSStoryboard.Name("Main"), bundle: nil).instantiateController(withIdentifier: NSStoryboard.SceneIdentifier("Document Window Controller")) as! NSWindowController)
    }
    
    override func printOperation(withSettings printSettings: [NSPrintInfo.AttributeKey : Any]) throws -> NSPrintOperation {
        return NSPrintOperation(view: PrintView(frame: CGRect(x: 0, y: 0, width: 100, height: 100)), printInfo: NSPrintInfo(dictionary: printSettings))
    }
 
}
 
class PrintView: NSView {
    
    override func knowsPageRange(_ range: NSRangePointer) -> Bool {
        print("knowsPageRange")
        range.pointee = NSRange(location: 1, length: 1)
        return true
    }
    
}

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Answer 1

DTS Engineer OP

Apple

3d

Hi. Thanks for filing a bug report. Looks like it has been dispatched over to the AppKit team for investigation. I'll check again and provide an update (if there's anything to report) next time I shuffle through forums posts with bug reports that I am tracking.

0

	class Document: NSDocument {

	override func makeWindowControllers() {
	addWindowController(NSStoryboard(name: NSStoryboard.Name("Main"), bundle: nil).instantiateController(withIdentifier: NSStoryboard.SceneIdentifier("Document Window Controller")) as! NSWindowController)
	}

	override func printOperation(withSettings printSettings: [NSPrintInfo.AttributeKey : Any]) throws -> NSPrintOperation {
	return NSPrintOperation(view: PrintView(frame: CGRect(x: 0, y: 0, width: 100, height: 100)), printInfo: NSPrintInfo(dictionary: printSettings))
	}

	}

	class PrintView: NSView {

	override func knowsPageRange(_ range: NSRangePointer) -> Bool {
	print("knowsPageRange")
	range.pointee = NSRange(location: 1, length: 1)
	return true
	}

	}