Drupal for facebook: auto log in to facebook account if Drupal account is linked

I am hoping to achieve a similar functionality to this site: www.lovecreativity.co.uk, whereby if you:

1) have facebook logged in, and...

2) have previously authorised the site...

3) it will automatically log you in.

This site is using the wp-facebookconnect plugin, which I have tried reverse engineering but it's a bit too intense.

I'm using the Drupal for Facebook module, which does not offer this functionality ("Logging into Drupal will never log you into facebook").

Currently, it will disconnect the user's facebook account between sessions, but I need it so that if you log in to the site using the site account, and have previously given access to the site, then it will automatically connect you again.

I've also tried finding documentation to answer my question but had no lu开发者_如何学运维ck at all, can anyone point me in the right direction?

edit: The requirement I have is that people must first have an account with the site, before being able to use FBC to share comments to their wall

Try the facebook connect module:

This module allows users to login on a Drupal website through the Facebook Connect API – using their Facebook login and password.