After trial and error, I was finally able implement the printing of a Base64 stream representing a PDF binary from a Windows 8 application.
I'm coding the app in HTML / CSS / WinJS. Essentially here is a brief explanation of how it was accomplished:
Create a new <canvas> element within the default.html file. Place it right after the open tag of the element. Like this:
<body role="application" class="app">
<canvas id="pdf-render-output"></canvas>
.
.
.
</body>
Then inside the default.css file, setup a few rules as well as a print media query. Like this:
body > canvas {
display: none;
}
.
. /* all your app's default css styles */
.
@media print {
body > * {
display:none;
max-width: 100%;
}
html {
max-width: 100%;
border-top-color: none;
border-top: 0;
}
body > canvas {
display: block;
border: none;
max-width: 100%;
width: 100%;
height: 100%;
position: relative;
}
}
Of note is the order in which the rules are declared in CSS. It's important to place the print media query after declaring default CSS rules.
After this is setup, javascript handles the rest. The basic idea is to render the PDF.js output to the "hidden" canvas in the DOM. When the document object gets sent to print, the CSS print media declaration is queried so that all elements under <body> are hidden except for the canvas element. Here is the javascript to print only the first page in the PDF:
//Define a container for the Base64 data we'll use with PDF.js
var pdfPrintData = {};
//Function to render PDF to canvas and begin printing contract with Windows 8 OS
printPrescription: function () {
var self = Application.navigator.pageControl,
printManager = Windows.Graphics.Printing.PrintManager.getForCurrentView();
self.getPDF().done(function () {
var pdfStream = pdfPrintData.base64,
pdfFile = convertDataURIToBinary(pdfStream);
PDFJS.disableWorker = true;
PDFJS.getDocument(pdfFile).then(function (pdf) {
var numPages = pdf.numPages,
renderCanvas = $('#pdf-render-output')[0];
//setup canvas
renderCanvas.height = pdf.getPage(1).data.getViewport(1).height;
renderCanvas.width = pdf.getPage(1).data.getViewport(1).width;
//Setup a render context for pdf.js to out a pdf file to the canvas.
var renderContext = {
canvasContext: renderCanvas.getContext('2d'),
viewport: pdf.getPage(1).data.getViewport(1)
};
//Bring up Windows 8 OS print after PDF is rendered to render context.
pdf.getPage(1).data.render(renderContext).then(function () {
printManager.onprinttaskrequested = self.onPrintTaskRequested;
Windows.Graphics.Printing.PrintManager.showPrintUIAsync();
});
})
});
},
onPrintTaskRequested: function (e) {
var self = Application.navigator.pageControl,
printTask = e.request.createPrintTask("Print Prescription", function (args) {
args.setSource(MSApp.getHtmlPrintDocumentSource(document));
printTask.oncompleted = self.onPrintTaskCompleted;
});
},
onPrintTaskCompleted: function (e) {
if (e.completion === Windows.Graphics.Printing.PrintTaskCompletion.failed) {
console.log("[ERX] : Failed to print!");
}
}
The self.getPDF method is just a function that retrieves the Base64 data stream, and that streams gets set on the .base64 property of the global pdfPrintData object. For some reason, I was not able to render the pdf using pdf.js to a dynamically create canvas in a dynamically created document. I had to render the output of the pdf.js render method to a canvas already present in the DOM.
