Incompatible with fabricjs 1.6.x

[ykh]

Hi 😄 Tnx for this nice library you had implemented. But, unfortunately it's not compatible with latest version of fabric js 1.6.x. Maybe you can fix this issue easily by a little change, although I couldn't found a clue in your code!

[tiesont]

For what it's worth, and for anyone else trying to figure this out, fabricjs-viewport works with fabricjs up through 1.6.0-rc.1 - after that, it fails silently. No idea why, either.

[sklipnoty]

I def. needed something like this, why hasn't this gone up river?