“Dark Horse” is an unexpected entry from Todd Solondz. The director of “Welcome to the Dollhouse,” “Happiness” and other movies that give new meaning to the term “black comedy” is known for pushing the envelope further than just about any other American filmmaker. His past work was filled with such troubling themes as pedophilia, rape and abortion.

But “Dark Horse” has none of that. And when it introduces us to its determinedly upbeat protagonist, Abe (Jordan Gelber), it appears that this might be a surprisingly upbeat comedy. But though there’s more optimism here than in the rest of his films put together, “Dark Horse” still contains the Solondz trademarks: unpleasant people who have resigned themselves to an unhappy ending that becomes a self-fulfilling prophecy.