Tim McGraw and Dwight Yoakam have both signed on for the same film. "Variety" says production has already begun on "Dirty Girl," a comedy about a teenage girl looking for her father, and her friendship with a boy who's gay and hasn't come out yet. Other stars on board for the flick include William H. Macy, Mary Steenburgen, and Milla Jovovich. "Dirty Girl" is slated to hit theaters next year. It's the second movie to feature both McGraw and Yoakam. The two country singers were also in the 2008 holiday comedy "Four Christmases."In recent years Yoakam has focused more on acting than music. His last album of original material was 2005's "Blame the Vain," while his last CD was the covers disc "Dwight Sings Buck." However, "Dirty Girl" will be Yoakam's tenth film since 2005. In addition to "Four Christmases" he's been in "Wedding Crashers," "The Three Burials of Melquiades Estrada," "Bandidas," "Crank" and its sequel, "Crank: High Voltage," "The Last Rites of Ransom Pride," "2:13," and "Provinces of Night." McGraw's other film credits include "The Blind Side," "The Kingdom," "Flicka," "Friday Night Lights," and "Black Cloud." He also has another film in the works, "Love Don't Let Me Down," in which he's starring opposite Gwyneth Paltrow.