Anyone get pdf.js working in a custom Widget?

New to custom Widget development so please point me in a different direction if this doesn’t make sense. So I have this idea of modifying the image annotator widget to use PDFs instead of images. In theory I should be able to do this using the Modzilla pdf.js library which should let me load a pdf into a HTML canvas element. However I have been stuck getting the pdf.js library imported and working in my widget, before I continue hacking away at it wondering if folks have already done this and can help me out here.

Here’s my widget javascript code:

var pdfData = atob(
    'JVBERi0xLjcKCjEgMCBvYmogICUgZW50cnkgcG9pbnQKPDwKICAvVHlwZSAvQ2F0YWxvZwog' +
    'IC9QYWdlcyAyIDAgUgo+PgplbmRvYmoKCjIgMCBvYmoKPDwKICAvVHlwZSAvUGFnZXMKICAv' +
    'TWVkaWFCb3ggWyAwIDAgMjAwIDIwMCBdCiAgL0NvdW50IDEKICAvS2lkcyBbIDMgMCBSIF0K' +
    'Pj4KZW5kb2JqCgozIDAgb2JqCjw8CiAgL1R5cGUgL1BhZ2UKICAvUGFyZW50IDIgMCBSCiAg' +
    'L1Jlc291cmNlcyA8PAogICAgL0ZvbnQgPDwKICAgICAgL0YxIDQgMCBSIAogICAgPj4KICA+' +
    'PgogIC9Db250ZW50cyA1IDAgUgo+PgplbmRvYmoKCjQgMCBvYmoKPDwKICAvVHlwZSAvRm9u' +
    'dAogIC9TdWJ0eXBlIC9UeXBlMQogIC9CYXNlRm9udCAvVGltZXMtUm9tYW4KPj4KZW5kb2Jq' +
    'Cgo1IDAgb2JqICAlIHBhZ2UgY29udGVudAo8PAogIC9MZW5ndGggNDQKPj4Kc3RyZWFtCkJU' +
    'CjcwIDUwIFRECi9GMSAxMiBUZgooSGVsbG8sIHdvcmxkISkgVGoKRVQKZW5kc3RyZWFtCmVu' +
    'ZG9iagoKeHJlZgowIDYKMDAwMDAwMDAwMCA2NTUzNSBmIAowMDAwMDAwMDEwIDAwMDAwIG4g' +
    'CjAwMDAwMDAwNzkgMDAwMDAgbiAKMDAwMDAwMDE3MyAwMDAwMCBuIAowMDAwMDAwMzAxIDAw' +
    'MDAwIG4gCjAwMDAwMDAzODAgMDAwMDAgbiAKdHJhaWxlcgo8PAogIC9TaXplIDYKICAvUm9v' +
    'dCAxIDAgUgo+PgpzdGFydHhyZWYKNDkyCiUlRU9G');  

loadScripts();

async function loadScripts() {
    console.log(`Loading script...`);
    const response = await fetch('https://mozilla.github.io/pdf.js/build/pdf.js');
    const responseBody = await response.text();
    const scriptElm = document.createElement("script");
    const inlineCode = document.createTextNode(responseBody);
    scriptElm.appendChild(inlineCode);
    document.body.appendChild(scriptElm);
    
    console.log(`Script successfully loaded`);

    const workerResponse = await fetch('//mozilla.github.io/pdf.js/build/pdf.worker.js');
    pdfjsLib.GlobalWorkerOptions.workerSrc = await workerResponse.text();
    
    console.log(pdfjsLib)
  
    var loadingTask = pdfjsLib.getDocument({ data: pdfData, });
loadingTask.promise.then(function(pdf) {
  console.log('PDF loaded');
  
  // Fetch the first page
  var pageNumber = 1;
  pdf.getPage(pageNumber).then(function(page) {
    console.log('Page loaded');
    
    var scale = 1.5;
    var viewport = page.getViewport({scale: scale});

    // Prepare canvas using PDF page dimensions
    var canvas = document.getElementById('the-canvas');
    var context = canvas.getContext('2d');
    canvas.height = viewport.height;
    canvas.width = viewport.width;

    // Render PDF page into canvas context
    var renderContext = {
      canvasContext: context,
      viewport: viewport
    };
    var renderTask = page.render(renderContext);
    renderTask.promise.then(function () {
      console.log('Page rendered');
    });
  });
}, function (reason) {
  // PDF loading error
  console.error(reason);
});
}

FWIW I am getting the following when I run the code: Error: Setting up fake worker failed: "Cannot load script at: /**

Any help greatly appriciated.

Hey @trwilson -

Just digging into this one right now. A few things stand out:

  • loadScripts() sometimes fails because the underlying library has nested dependencies it is trying to download. This often is the case with large Js libraries (with lots of their own dependencies)
  • When running this code within a HTML file, It also fails to load. This is generally my first check to debug behavior I think is tied to something specific to CWs.
<html>
<head>
	<script type="text/javascript">
		var pdfData = atob(
    'JVBERi0xLjcKCjEgMCBvYmogICUgZW50cnkgcG9pbnQKPDwKICAvVHlwZSAvQ2F0YWxvZwog' +
    'IC9QYWdlcyAyIDAgUgo+PgplbmRvYmoKCjIgMCBvYmoKPDwKICAvVHlwZSAvUGFnZXMKICAv' +
    'TWVkaWFCb3ggWyAwIDAgMjAwIDIwMCBdCiAgL0NvdW50IDEKICAvS2lkcyBbIDMgMCBSIF0K' +
    'Pj4KZW5kb2JqCgozIDAgb2JqCjw8CiAgL1R5cGUgL1BhZ2UKICAvUGFyZW50IDIgMCBSCiAg' +
    'L1Jlc291cmNlcyA8PAogICAgL0ZvbnQgPDwKICAgICAgL0YxIDQgMCBSIAogICAgPj4KICA+' +
    'PgogIC9Db250ZW50cyA1IDAgUgo+PgplbmRvYmoKCjQgMCBvYmoKPDwKICAvVHlwZSAvRm9u' +
    'dAogIC9TdWJ0eXBlIC9UeXBlMQogIC9CYXNlRm9udCAvVGltZXMtUm9tYW4KPj4KZW5kb2Jq' +
    'Cgo1IDAgb2JqICAlIHBhZ2UgY29udGVudAo8PAogIC9MZW5ndGggNDQKPj4Kc3RyZWFtCkJU' +
    'CjcwIDUwIFRECi9GMSAxMiBUZgooSGVsbG8sIHdvcmxkISkgVGoKRVQKZW5kc3RyZWFtCmVu' +
    'ZG9iagoKeHJlZgowIDYKMDAwMDAwMDAwMCA2NTUzNSBmIAowMDAwMDAwMDEwIDAwMDAwIG4g' +
    'CjAwMDAwMDAwNzkgMDAwMDAgbiAKMDAwMDAwMDE3MyAwMDAwMCBuIAowMDAwMDAwMzAxIDAw' +
    'MDAwIG4gCjAwMDAwMDAzODAgMDAwMDAgbiAKdHJhaWxlcgo8PAogIC9TaXplIDYKICAvUm9v' +
    'dCAxIDAgUgo+PgpzdGFydHhyZWYKNDkyCiUlRU9G');  
​
loadScripts();
​
async function loadScripts() {
    console.log(`Loading script...`);
    const response = await fetch('https://mozilla.github.io/pdf.js/build/pdf.js');
    const responseBody = await response.text();
    const scriptElm = document.createElement("script");
    const inlineCode = document.createTextNode(responseBody);
    scriptElm.appendChild(inlineCode);
    document.body.appendChild(scriptElm);
    
    console.log(`Script successfully loaded`);
​
    const workerResponse = await fetch('http://mozilla.github.io/pdf.js/build/pdf.worker.js');
    pdfjsLib.GlobalWorkerOptions.workerSrc = await workerResponse.text();
    
    console.log(pdfjsLib)
  
    var loadingTask = pdfjsLib.getDocument({ data: pdfData, });
loadingTask.promise.then(function(pdf) {
  console.log('PDF loaded');
  
  // Fetch the first page
  var pageNumber = 1;
  pdf.getPage(pageNumber).then(function(page) {
    console.log('Page loaded');
    
    var scale = 1.5;
    var viewport = page.getViewport({scale: scale});
​
    // Prepare canvas using PDF page dimensions
    var canvas = document.getElementById('the-canvas');
    var context = canvas.getContext('2d');
    canvas.height = viewport.height;
    canvas.width = viewport.width;
​
    // Render PDF page into canvas context
    var renderContext = {
      canvasContext: context,
      viewport: viewport
    };
    var renderTask = page.render(renderContext);
    renderTask.promise.then(function () {
      console.log('Page rendered');
    });
  });
}, function (reason) {
  // PDF loading error
  console.error(reason);
});
}
	</script>
</head>
</html>

I haven’t played much with anything outside of png, jpg, and base64 encoding for images, so I cant provide too much additional insight on this one.

Pete