One way to know if a movie is a classic is to discover yourself feeling pity for another movie about how it was made. Pity this true-if-syrupy Hollywood story of Emma Thompson as Mary Poppins author P.L. Travers in stubborn negotiations with a Walt Disney played by Tom Hanks. As Saving Mr. Banks has it, Travers very reasonably loathed the thought of her stories being made into a Disney movie — until dire financial straits led her to reconsider and to reflect on the troubled upbringing from whence her young imagination had spawned the famous enchanted nanny in the first place. Crucial to that inspiration was Travers’ father, played here by Colin Farrell in drawn-out flashbacks as a doting, consumptive drunk. Well, Walt, as he insisted on being called, was a dad too, who’d sworn to his own daughters that he’d bring Mary Poppins to the big screen, even if it took 20 years of diplomacy with the intransigent, stiff-upper-lipped Travers. “These books simply do not lend themselves to chirping and prancing,” she protests. “No. Certainly not a musical.” But with the mighty Sherman brothers (Jason Schwartzman and B.J. Novak) on songwriting duty, resistance apparently was futile. Along with Paul Giamatti as Travers’ L.A. chauffeur, Thompson and Hanks get cozy in their zones, perfectly content to melt your heart. This too is a Disney movie, of course, with little to say about artistic integrity but lots of commonsense encouragement to revisit Mary Poppins.