I'm not too sure if there is an 'official'/ correct solution to this, but a workaround that could work (though I'm not sure if it would be hugely effective) would be to momentarily change the view to encompass the entire layout for the moment before the snapshot is taken, before returning to the regular view. That way even if the snapshot is purely the current view, it would be a view of the entire canvas.
If you did it within a small space of time, chances are the user wouldn't even notice.
I hope this helps somehow!
Regards,
Gideon