SAN FRANCISCO - Apple is expected to unveil its latest take on the iPhone Tuesday during an annual ritual that will probably cast a spotlight on the gadget maker's drive to regain market share and its sluggish pace of innovation. In keeping with its tight-lipped ways, Apple Inc. hasn't disclosed what's on the agenda for the coming-out party scheduled to begin at 10 a.m. PDT at its Cupertino, Calif. headquarters. But this is the time of year that Apple typically shows off the latest generation of its iPhone, a device that has reshaped the way people use computers since its debut in 2007. Apple took the wraps off the iPhone 5, the current model, last September. The company has never waited longer than a year to update the iPhone, which has generated $88 billion in revenue during the past year. Apple's timetable for rolling out products has vexed many investors who have watched the company's growth slow and profit margins decrease. Meanwhile, a bevy of smartphone makers, most of whom rely on Google Inc.'s free Android software, release wave after wave of devices that cost less than the iPhone. Those concerns are reflected in Apple's stock price, which has declined nearly 30 percent since peaking at $705.07 at about the same time the iPhone 5 went on sale last year. The Standard & Poor's 500 index has risen about 14 percent during the same stretch. Even though Apple's market value of roughly $460 billion is more than any other company in the world, the deterioration in its stock price is escalating the pressure on CEO Tim Cook to prove he's the right leader to carry on the legacy of co-founder Steve Jobs. Since Cook became CEO two years ago, Apple has only pushed out new versions of products developed under Jobs, raising questions about whether the company's technological vision has become blurred under the new regime. In public appearances, Cook has repeatedly said Apple is working on some exciting breakthroughs without revealing details. The company is believed to be working on a so-called "smartwatch" that would work like a wrist-bound smartphone. Samsung Electronics, one of Apple's biggest rivals, introduced its own $300 smartwatch called Gear last week, as did Sony and Qualcomm Inc.