If you will use webix and requirejs together, you will get an error like this.
TypeError: window.html2canvas is not a function
toPNG topng.js:31
u promiz.js:310
a promiz.js:286
u promiz.js:301
<anonymous> promiz.js:15
EventListener.handleEvent* promiz.js:8
<anonymous> webix.js:8
<anonymous> webix.js:8