How to implement acrobat-like inherit zoom

[iamryanchia]

I want to know how to make the zoom not change when the bookmark is clicked. In other words, when I set the zoom to 0.5, after clicking the bookmark, it can maintain the previously set zoom. This is called "inherit zoom" in acrobat.

I have noticed a key argument fit in addbookmark() function. And i tried it, but failed. Is there any ways to achieve the effects mentioned above? Thank you in advance.