Cancel UWP Print Task

Question

I'm implementing a print feature in a UWP app, and I cannot find any nice way to cancel the print task after clicking Print on the preview page. Our users may be printing dozens or even hundreds of pages at a time, which takes awhile to send to the printer, so having a cancel option is very important.

The user's workflow is:

1. Select some pages to print
2. Configure some custom print options
3. Show the Print UI with the preview (PrintManager.ShowPrintUIAsync())
4. Click print
5. Show a progress bar/status while the job is being sent to the printer. This can take awhile, so a cancel option needs to be available here.

I'm following the print sample: https://github.com/microsoft/Windows-universal-samples/tree/master/Samples/Printing I cannot find any way to cancel in PrintManager, PrintTask, PrintTaskRequest, AddPagesEventArgs, PrintTaskProgressingEventArgs, etc.

My only idea is to use a CancellationTokenSource and throw if cancellation is requested, but this seems like a hacky workaround. Am I missing something?

Answer 1

I can sort of cancel if I use a CancellationTokenSource and check for cancellation in the AddPages event handler.

protected async void AddPrintPages(object sender, AddPagesEventArgs args)
        {
            PrintDocument printDoc = (PrintDocument)sender;
            for ( uint i = 0; i < _pageCount; i++)
            {
                if (_cancellationToken.IsCancellationRequested) 
                    break;

                 var page = await GetPrintPageAsync(i)
                 printDoc.AddPage(page);
            }           

            printDoc.AddPagesComplete();
        }

This skips the remainder of the pages, but any pages that have already been added to the print doc will still be sent.