Thanks for your reply,
I'm not sure what the getter / setter API is, I just use the standard Hype app with no extras. So I guess I don't.
The problem I have is:- when I right click, it seems to break the drag action and the webpage follows the arrow cursor, even though the mouse button has been released. It basically becomes unusable if someone accidentally clicks the right mouse button.
I am on Safari 6.2.7 on OS X 10.8.5, things may have improved with later versions of Safari. I'll test my site on Yosemite when I get home.