In writer-director Mike Mills’ touchingly autobiographical new film, a commitment-phobic graphic artist is supportive but bewildered when his father comes out of the closet at 75, just in time to face a terminal illness. Stars Ewan McGregor and Christopher Plummer radiate subtle tenderness, with Mélanie Laurent and Goran Visnjic enlivening slightly underwritten roles as the son’s and father’s respective love interests. As in his first film, the glassy coming-of-age snapshot Thumbsucker, Mills reflexively reaches for his CD-cover and music-video bags of tricks, accumulating indie quirk and risking a veneer of breadth at the expense of depth; Beginners does get a little fidgety flashing back and forward in time and cycling through arty concepts. But gradually these mannerisms come to seem less about showing off than about laying bare an authentic, affecting introspection. It recalls not the shallow clutter of Michel Gondry but the maturely tragicomic profundity of mid-vintage Woody Allen, deftly transposed into the milieu of a media-saturated generation whose good fortune, Mills’ protagonist confesses, “allowed us to feel a sadness our parents didn’t have time for.” Watching this gently assured and open-hearted film gives an unshakable sense that Mills is on his way toward making a masterpiece.