I'm trying to change the selection area of a `UIBarButtonItem` within the navigation controller. Basically I'm trying to change the allowable area that will make that `UIBarButtonItem` selectable. Right now, the size of my `UIBarButtonItem` is 40x40, but I can easily select it even if my finger is not touching the button at all.

Here's to illustrate what I mean:

[![enter image description here](https://i.stack.imgur.com/YCD0r.png)](https://i.stack.imgur.com/YCD0r.png)

The green represents the size of the `UIBarButtonItem`. The red represents the allowable area that makes the `UIBarButtonItem` selectable.

How can I change the width of the red area?

Here's a snippet of code if helpful:

```
changeMuscleMap = UIButton(frame: CGRect(x: 0, y: 0, width: 40, height: 40) )
changeMuscleMap.setImage(UIImage(named: "change"), forState: .Normal)
navigationItem.leftBarButtonItem = UIBarButtonItem(customView: changeMuscleMap)

```

Thanks!