It's impossible for now.
It's what I call the "Box in a Box" model. You get control of the box inside of the box (the UIViewController
inside of the UIPopoverController
), but you have very limited control over the actual popover itself. Outside of the arrow direction and the size, you can't change much else. There are also options for a modal effect popover, which dims everything else when it shows up, but I haven't tried to get it working.
I'm sure you've noticed there is no UIPopover
class by now.
The answer you want to hear:
If you really want to style one that bad, just write your own. It's really not that hard.