如何在SwiftUI上打印文本和图像的macOS视图？

Question

我试图在SwiftUI上打印macOS视图的内容。根据文档，这似乎是通过给NSPrintOperation一个由NSHostingView创建的NSView来实现的。SwiftUI视图的主体包含几个文本视图和一个图像视图，这些视图周围有边框。所有文本都会被打印出来，但是图像和边框是不可见的。要让这件事成功，还需要别的什么吗？

这里有一个示例来演示这个问题。只需创建一个新的macOS应用程序，用下面的代码替换ContentView，然后启用签名和功能中的打印：

struct ContentView: View {
    
    var body: some View {
        VStack {
            Button("Print", action: self.onPrint )
            Divider()
            Print_Preview()
        }
    }
    
    private func onPrint() {
        let pi = NSPrintInfo.shared
        pi.topMargin = 0.0
        pi.bottomMargin = 0.0
        pi.leftMargin = 0.0
        pi.rightMargin = 0.0
        pi.orientation = .landscape
        pi.isHorizontallyCentered = false
        pi.isVerticallyCentered = false
        pi.scalingFactor = 1.0
                
        let rootView = Print_Preview()
        let view = NSHostingView(rootView: rootView)
        view.frame.size = CGSize(width: 300, height: 300)
        let po = NSPrintOperation(view: view, printInfo: pi)
        po.printInfo.orientation = .landscape
        po.showsPrintPanel = true
        po.showsProgressPanel = true
        
        po.printPanel.options.insert(NSPrintPanel.Options.showsPaperSize)
        po.printPanel.options.insert(NSPrintPanel.Options.showsOrientation)
        
        if po.run() {
            print("In Print completion")
        }
    }
    
    struct Print_Preview: View {
        var body: some View {
            VStack(alignment: .leading) {
                Text("Bordered Text Above Bordered Image")
                    .font(.system(size: 8))
                    .padding(5)
                    .border(Color.black, width: 2)
                Image(systemName: "printer")
                    .resizable()
                    .padding(5)
                    .border(Color.black, width: 2)
                    .frame(width: 100, height: 100)
                Text("Bordered Text Below Bordered Image")
                    .font(.system(size: 8))
                    .padding(5)
                    .border(Color.black, width: 2)
            }
            .padding()
            .foregroundColor(Color.black)
            .background(Color.white)
            .frame(width: 200, height: 200)
        }
    }

}

这里还有应用程序和打印面板的截图。

​

​

​

​

Answer 1

感谢@Willeke给出了带有指针的评论，并感谢@ that 2120275提出了一个不同的问题，而这个问题恰好包含了解决问题所需的技巧。解决方案是从NSImageView返回的NSView中创建NSHostingView，然后打印该NSImageView而不是原始的NSView。

通过替换这两行代码，可以使上面的示例代码正常工作：

view.frame.size = CGSize(width: 300, height: 300)
let po = NSPrintOperation(view: view, printInfo: pi)

有以下几点：

let contentRect = NSRect(x: 0, y: 0, width: 300, height: 300)
view.frame.size = contentRect.size

let newWindow = NSWindow(
    contentRect: contentRect,
    styleMask: [.titled, .closable, .miniaturizable, .resizable, .fullSizeContentView],
    backing: .buffered, defer: false)
newWindow.contentView = view

let myNSBitMapRep = newWindow.contentView!.bitmapImageRepForCachingDisplay(in: contentRect)!
newWindow.contentView!.cacheDisplay(in: contentRect, to: myNSBitMapRep)

let myNSImage = NSImage(size: myNSBitMapRep.size)
myNSImage.addRepresentation(myNSBitMapRep)

let nsImageView = NSImageView(frame: contentRect)
nsImageView.image = myNSImage

let po = NSPrintOperation(view: nsImageView, printInfo: pi)