facebook canvas page: app behavior dependent of visitor to user's profile

The problem:

I want to provide a facebook application as开发者_运维知识库 canvas page to user A ('the owner'). If user A is seeing the app via in its profile, the app should exhibit behavior Ba.

If there is a user B ('the visitor') which is visiting the owners profile and clicking to see the app's canvas page in the owner's profile, the app should exhibit behavior Bb according to the visitor's profile. The visitor (user B) does not have the application in its profile.

An analogy would be that an application like bandpage in a band's profile (http://www.facebook.com/hmbmusic?sk=app_178091127385) would have different behavior according to each person visiting the profile.

I've been one day researching stuff fb_sig_user and fb_sig_canvas_user and can not come to a conclusion over if it this possible to do something like this or not.

Is it possible? Any tips?

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It's possible. Once a user authorizes your app you'll have access to their ID and can make decisions as to who they are. Additionally if you're coming in to your app from different endpoints you can use the URL to make decisions from.

You'll need to decode the signed request that's passed to your app to see if the user has added the app yet or not. Start your research with the signed_request and that should get you headed in the right direction.