offer facebook connect when user visits wordpress blog

Is there a way to detect if a user is logged in at facebook when he or she is v开发者_开发百科isiting your wordpress blog, and then offer to connect with facebook such that he is instantly logged in at your blog?

There's no way of knowing if a user is logged in to Facebook unless they've authorized your app (at which point, you have what you need) for privacy reasons. I would offer Facebook Connect to all visitors of your blog (discretely, of course) with an option to hide the Connect box/area in the future (like Ars Technica; scroll down about a third of the page and you'll see an fb:like-box with a "Disable Facebook on Ars Technica" underneath). This will give your visitors a chance to connect to Facebook, but won't annoy those who never want to hear about Facebook again.