I have, I believe, made significant progress. Having tidied up the code, I've largely thrown it away and have new code that gives me the ability to print my HTML content and, most importantly, the ability to add a page header and footer to my prints. The headers and footers was a right pain to work out, so I'm posting the raw code here on the off-chance that someone other than me actually wants to print stuff on actual paper. I will need to code review and tidy it up before I call it production!
I created a struct to contain my printing options. This is just a useful way of grouping options when I'm prety sure that the options list will grow and when the function signature starts to grow too long. I now create a PrintOptions instance for my parameters:
public struct PrintOptions {
var header: String
var footer: String
var htmlContent: String
}
My HTMLPrintView class is now an extension of WKWebView. It has to be that because I need to override the drawPageBorder function and the override didn't work when I used NSView with an embedded WKWebView:
public class HTMLPrintView: WKWebView {
var pop: NSPrintOperation?
var printOptions: PrintOptions?
public override func drawPageBorder(with borderSize: NSSize) {
super.drawPageBorder(with: borderSize)
guard let pop,
let printOptions
else { return }
// Drawing the header
let headerAttributes: [NSAttributedString.Key: Any] = [
.font: NSFont.systemFont(ofSize: 10),
.foregroundColor: NSColor.black
]
let headerString = NSAttributedString(string: printOptions.header, attributes: headerAttributes)
headerString.draw(at: NSPoint(x: 30, y: borderSize.height - 50))
// Drawing the footer
let footerAttributes: [NSAttributedString.Key: Any] = [
.font: NSFont.systemFont(ofSize: 10),
.foregroundColor: NSColor.black
]
let footerString = NSAttributedString(string: printOptions.footer,
attributes: footerAttributes)
footerString.draw(at: NSPoint(x: 30, y: 30))
let pageString = NSAttributedString(string: "Page \(pop.currentPage)",
attributes: footerAttributes)
pageString.draw(at: NSPoint(x: borderSize.width - 80, y: 30))
}
public func printView(printOptions: PrintOptions, window parentWindow: NSWindow) {
loadHTMLString(printOptions.htmlContent, baseURL: nil)
DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
let printInfo = NSPrintInfo()
printInfo.horizontalPagination = .fit
printInfo.verticalPagination = .fit
printInfo.topMargin = 60
printInfo.bottomMargin = 60
printInfo.leftMargin = 40
printInfo.rightMargin = 40
printInfo.isVerticallyCentered = false
printInfo.isHorizontallyCentered = false
self.pop = self.printOperation(with: printInfo)
self.printOptions = printOptions
self.pop!.printPanel.options.insert(.showsPaperSize)
self.pop!.printPanel.options.insert(.showsOrientation)
self.pop!.printPanel.options.insert(.showsPreview)
self.pop!.view?.frame = NSRect(x: 0.0, y: 0.0, width: 300.0, height: 900.0)
self.pop!.runModal(
for: parentWindow,
delegate: self,
didRun: nil,
contextInfo: nil
)
}
}
}
drawPageBorder is called every time a logical page is created... so it can be called a lot. I've coded it such that it will do nothing other than call the super class function if we are not currently printing. If we have a printOperation and we have printOptions, then we must be in the process of printing the page, so I drop into the code that adds the header and footer text to the page and that prints the page number (bottom right). It's important NOT to try and keep track of the current page yourself, as I could see no way to reliably know when a page is being printed or displayed (such as in the print preview). Instead, the printOperation provides us with a page number to use.
It's also important that this run on the main thread. Hence the DispatchQueue.main.asyncAfter call. This gives the web view 1 second to load the HTML and puts the print operation on the main thread.
In my calling code, I have access to the windowNumber of the SwiftUI window, so can look up the NSWindow and pass that to my print routine. Without the window, I have found it impossible to print.
func printSelected() {
guard let selection else { return }
let baseHtml = htmlText(node: selection)
let htmlDocument = buildHtml(formattedNote: baseHtml, title: "Outline Print")
guard let window = NSApplication.shared.windows.first(
where: {$0.windowNumber == self.windowNumber})
else { return }
let printView = HTMLPrintView()
let options = PrintOptions(
header: "Heading String",
footer: "Footing String",
htmlContent: htmlDocument
)
printView.printView(printOptions: options, window: window)
}
Don't know if this will help anyone else, but hope it does.
Steve
