iOS 6 sharing like Messages, not like Photos (UIActivityViewController and UIDocumentInteractionController)

Question

In iOS 6, tapping the action button in the Photos app presents the standard UIActivityViewController:

Doing the same from Messages presents a different set of options. This looks to me like it's using the UIDocumentInteractionController api to pull all the apps that say they can handle an image.

My question is twofold:

1. How does one get into the Messages action menu? Tumblr and Halftone, to name a few, have done it... I can't seem to find the documentation.

2. How does one show the Messages-style action menu? When I present a UIActivityViewController it doesn't have those options... just the standard set facebook/twitter/copy/print/save to camera roll/etc.

Thanks!

Answer 1

How to get on that list: "Registering the File Types Your App Supports"

To handle images, you probably want to register for public.image (Reference)

To present that list, you just need to ask a UIDocumentInteractionController to display its options menu