Wait for fonts being loaded before image rendering

static/canvas.js

@@ -125,7 +125,7 @@ for (let i = 0; i < navButtons.length; ++i) {
   }
 }
 
-window.onload = function() {
+window.addEventListener('load', function() {
   // Display correct tab
   let hash = window.location.hash || '#step1';
   document.querySelector('nav > a[href="#step3"]').click();
@@ -161,8 +161,10 @@ window.onload = function() {
   document.getElementById('signature').oninput = draw;
 
   // Update canvas
-  draw();
-}
+  document.fonts.ready.then(function() {
+    draw();
+  });
+});
 
 let randomElement = function(selector) {
   let elems = document.querySelectorAll(selector);