The following feedback was sent to us via owencm@ (who posted it to the WICG bug tracker: https://github.com/WICG/web-share/issues/16):

I'm actually working on a collaborative whiteboard application. I wanted to share the drawings on the canvas as an image. I generated the image and tried to share it using such a code:

let url = canvasElement.toDataURL('image/png');

navigator.share({
title: document.title,
text: "Shared whiteboard",
url: url
}).then(() => console.log('Successful share'))
.catch(error => console.log('Error sharing:', error));

However, I got an exception:
"Error sharing: DOMException: Must be handling a user gesture to perform a share request."

I would say this was quite unexpected, because I was clicking on a button in the same way as with the sharing of a regular URL. I'm not sure why this user gesture was not accepted.
Moreover, is sharing of images in such a way supported?