He may be staring down the barrel of his 50th birthday, but that hasn’t put a crimp in Billy Idol’s ability to leer.

Ask the famously randy star about his gig at next week’s high-profile South by Southwest festival, and he says, with a snicker, “I’ll be playing onstage with those lovely girls The Donnas, so they’re fair game.”

Bring up his self-satirizing role in Adam Sandler’s 1998 movie “The Wedding Singer” and he says, “I got to shag one of the flight attendants in the movie. Rent it and guess which one.”

Allude to his new single, “Scream,” which is about, er, oral pleasures, and Idol says, “Well, ‘My Ding-A-Ling’ was Chuck Berry’s biggest record. So it seemed like a good idea.”

In fact, Idol will need a lot of good ideas to rebrand himself as a relevant pop star. Twelve long years have passed since he last put out an album of original material — an epic wander in the desert that finally ends later this month with the release of “Devil’s Playground.”

In the intervening time, Idol got on and off crack, overdosed, experienced a life-threatening motorcycle accident and suffered the end of a second long-term relationship.

“I was going into a dark place,” he says. “I was burned out after 20 years of balls-to-the-walls, blazing, we-don’t-give-a-damn, there-ain’t-no-future, live-for-now (attitude). I was losing youthful energy.”

He was also turning into a cartoon. With his seemingly permanent sneer and endless fist-pumps plastered all over MTV, Idol started to seem as contrived as his name. When grunge came in, he got lumped in with the hair bands as a sexist anachronism.

Drugs and overworked

Idol says things had been going south for a long time due to drugs and overwork. Even during his commercial peak, in 1987, he says, “I can remember staying up for three weeks doing crack. I’d (think) people were filming me and I was hearing people in the next apartment talking about me.”

Watching an MTV interview in 1990, Idol recalls that he thought to himself, “It seems like I’m dead already.”

His sales began to slump with 1993’s “Cyberpunk.” The next year Idol had his O.D. His record company, EMI, still wanted him to make a record. But the label and the star had very different ideas of what it should sound like. The singer says they wanted “Billy Idol lite.”

Yet Idol says the project’s collapse encouraged his personal turnaround. He wound up spending more time at home, becoming a real father for the first time to his son, now 16.

“Instead of the ivory tower of being in a band, I was actually out there on the baseball diamond (with my son),” he says. “I sang the national anthem for his Little League team. Having to take him to school, having that responsibility, made me deal with real life,” he says.

Rebuilding career

He now feels it was beneficial to his music that his late-’90s record was shelved. “The worst thing would have been to chase fashion, to make a grunge record or some pop thing to fit in,” he says.

Instead, Idol began rebuilding his career with the help of the music that had made him big to begin with. EMI issued a “Greatest Hits” package in 2000, expecting it to sell around 100,000 copies. But it’s sold more than 940,000 so far, according to SoundScan. Meanwhile, Idol reunited with his main guitarist, Steve Stevens, and began touring again, with mounting success.

Noting the popularity of the hits album, VH1 awarded Idol a “Storytellers” episode, further upping his profile.

Yet all those efforts still milked nostalgia. They didn’t argue for a new Idol. It wasn’t until a 2003 concert at Hammerstein Ballroom that Sanctuary Records approached Idol about making new music in his older style.

An ’80s revival has since kicked into high gear. Mtley Crüe recently reunited for a sold-out arena tour and Velvet Revolver brought the musicians from Guns N’ Roses back to the top of the charts. “Watching Slash (come back) gave me hope,” Idol says of the Velvet guitarist. “It made me think, ‘There’s life after death.”‘