The
fabric.Control is not a constructor
issue has to do with the version of fabric.js that you are using.
The error does not occur with
version: "4.1.0"
Get the script tag
here
The
Cannot read property 'add' of null
error is occurring because your
iframeDocument.getElementById('c');
is handing back a null. So... does the document in the iframe contain a canvas with id='c'?
If it
does, then where you're getting the iframe document, maybe try like this?
var iframe = document.getElementById('myiframe');
var iframeDocument = iframe.contentDocument || iframe.contentWindow.document;
Good luck!