'Don Jon' lays bare a naked truth: A romantic comedy built around porn can be insightful, clever and raunchy fun.

Scarlett Johansson plays his perfect opposite number. Barbara Sugarman's a gum-smacking beauty determined to "sophisticate" her life, turn that blue collar white on any potential mate. Julianne Moore is the film's X-factor — what she brings you won't see coming. Tony Danza's ranting dad, Jon Sr., is such a meatball — both consuming them and that ever-present plate of spaghetti with remarkable gusto and embodying that very specific male type — that I'm really hoping Hollywood is reminded of what a swell tough Danza can be.

Much of "Don Jon's" likability is because of its unapologetic frankness. Case in point: The film opens with Jon pointing out all the things he loves in his life — and Jon really loves his porn. He practices daily and religiously. Be forewarned, on this front "Don Jon" represents. The imagery is bodacious, bountiful and graphic.

So how did a movie about porn turn into a clever romantic comedy and, gulp, manage to be so meaningful?

Certainly a great deal of credit goes to Gordon-Levitt for his shrewd take on the topic. But it feels as if something larger is afoot. With films like "Don Jon" and, earlier this summer, the caustic apocalyptic pop of "This Is the End," perhaps R-rated comedy is moving past its mindless "Hangover" phase.

"Don Jon" is definitely smarter than your average R. It's as if the 32-year-old actor has taken everything he's learned — working with directors as diverse as big-vision Christopher Nolan and artful-indie Jonathan Levine and roles as distinct as the time-traveling hitman in "Looper" and his love-struck cancer patient in "50/50" — and rolled the collective wisdom into "Don Jon."

As a result, Jon is no one-dimensional dude. Sure, he may be addicted to porn, but he's seriously devoted to his boys, Bobby (Rob Brown) and Danny (Jeremy Luke), and his family, silent-texting sister Monica (Brie Larson milking the dialogue she's given), dad and a slightly hysterical mom (Glenne Headly).

There is his body too, gym-toned to perfection; his wheels, a vintage Chevy Chevelle SS; and his church, Catholic, to which he is faithful. Every Sunday he's there with the family, followed by confession — his primary sins masturbation and sex out of wedlock. A few Hail Marys, a clean slate and Jon is set for the week ahead.

Until the night Barbara shows up at the bar. She might be "the one," and the nagging sense that Jon may actually want something more than sex sets up the major axis on which the film turns.

On the surface, much of the humor is derived from baser instincts. The way Jon describes his dedication to porn is remarkably scientific and with a precision Masters and Johnson could only dream about. You do begin to understand what watching does for him and why he finds it more satisfying than the real thing, though lord knows he has plenty of that too.

But in using porn as Jon's touchstone and the Leonardo DiCaprio-Kate Winslet "Titanic" affair as Barbara's, Gordon-Levitt has zeroed in on the central friction of media-enhanced romantic expectations. Johansson is excellent in taking Barbara from tease to torturer, wielding her sexuality like a club. The couple's clashing ideals come into sharp focus during a heated argument over the merits of Swiffer. Yes, a mop makes a major mess. The humor tempered by hurt is classic.

The movie never forgets that relationships are messy too. Moore turns up as Ester, an unconventional complication. Jon first spots the sobbing woman at his night class and steers clear. When she wanders over to apologize and catches him watching porn on his cell, Jon's world view shifts again.

Gordon-Levitt peels back yet another layer of gender politics in their relationship. There is the age difference, and there is the sex. But it is in bridging the intellectual divide between them that the film gets interesting.

The acting is fine all around, but Gordon-Levitt is the anchor, wearing that Jersey accent like he was born with it. The crew, from camera to set design, does its work to keep that vibe going. It suits one of the film's smart secondary themes particularly well, that of the working class. Watching Jon behind the wheel of his souped-up Chevy shouting F-bombs at the idiots on the road, then seeing Jon Sr. hurling the same epithets at the idiots on TV, you see the traditions that bind father and son.

And if the plotting and the romancing in "Don Jon" goes slightly soft at the end, can't we forgive a guy a little sentimentality? Geez.

betsy.sharkey@latimes.com