Eye contact question?

At what point is eye contact passing “just being nice”. I have had some occasions with a friend where when we are talking it’s just solid eye contact. I am actually not used to that level of eye contact, to me it’s just rock solid staring while talking. It’s happened a couple of times. Sometimes it’s like no one else is around even though we are at a table with other people. He’s smiling and talking with me. But at what point is it something more how do you gauge that time? I find myself breaking it only for it to just snap right back.
Eye contact question?
Post Opinion