On Boredom

Is boredom an emotion or a way we view the world? This has been a question that I was thinking about while on a particularly boring weekend in order to try to entertain myself (I do philosophy when bored.). Opposed to other emotions, boredom alters the way  one perceives the world more drastically than I would say others do. Other emotions tend to focus on the self (ex: I feel good because I am happy, I feel bad because I am sad), boredom seems to focus on external objects. When bored, one perceives the external world without any interest. One is indifferent, and it seems more like there is an absence of emotions or fascination with one's world. However, it still provokes a response in the mind. Boredom can be the cause of much mental anguish, and some might say that this pain implies that boredom is an emotion. However pain is not an emotion. It can make one sad or angry, but pain in itself is not an emotion, so why should boredom be defined in that manner?