Question

Is it possible to make a Facebook wall post using the FB.ui but without showing the pop up dialog box to the user ?

Answer 1

No, not with FB.ui. To post directly to the users wall without a dialogue you would have to use FB.api. To do this the user will have to be logged in and have granted your app the publish_stream permission. The code example from the documentation:

var body = 'Reading JS SDK documentation';
FB.api('/me/feed', 'post', { message: body }, function(response) {
  if (!response || response.error) {
    alert('Error occured');
  } else {
    alert('Post ID: ' + response.id);
  }
});

Be aware though that Facebook dislikes direct wall posting, and unless the content you are posting is a direct result of the user’s interaction with the flow of your app, you run the risk of being flagged as spam and having your app suspended. From the platform policy (section IV):

.2. You must not pre-fill any of the fields associated with the following products, unless the user manually generated the content earlier in the workflow: Stream stories (user_message parameter for Facebook.streamPublish and FB.Connect.streamPublish, and message parameter for stream.publish), Photos (caption), Videos (description), Notes (title and content), Links (comment), and Jabber/XMPP.

.3. If a user grants you a publishing permission, you must still obtain consent from the user before taking any action on the user’s behalf, such as publishing content or creating an event.

From personal experience, Facebook will insist on your app notifying the user in some way before taking any publish action. This won’t stop you putting an app live that contravenes their policies, but if their app monitoring team pick up on it they can and will suspend the app until you make the required changes.