And the external code thats calling the change to the iframe
Also using a rect with your own iframe code may help solve this.. see this thread.
Also an idea without seeing exactly what you are doing would be to put this code in your head that declares the widget element in a global var.
Then you should be able to target it's iframe via querySelector.
<script>
function myCallback(hypeDocument, element, event) {
HTMLWidget_ =hypeDocument.getElementById('HTMLWidget')
return true;
}
if("HYPE_eventListeners" in window === false) {
window.HYPE_eventListeners = Array();
}
window.HYPE_eventListeners.push({"type":"HypeSceneLoad", "callback":myCallback});
</script>
External button
<button type="button" onclick="HTMLWidget_.querySelector('iframe').setAttribute('src', 'rect.html');">Click Me!</button>
Can only test this on iOS simulator at the mo.