Apple released OS X 10.9.3 Mavericks Thursday, an update that improves support for large, high-resolution displays and paves the way for Apple itself to embrace that technology.
The update "improves 4K display support on Mac Pro (Late 2013) and MacBook Pro with 15-inch Retina Display (Late 2013)," according to the update description. In practice that means external displays with lots of pixels -- 4K displays start at 3,840x2,160 -- can better handle the smooth fonts and crisp images possible through Apple's Retina display technology.
Such displays pack pixels more densely -- thus the descriptive term HiDPI, for high dots per inch. Apple has brought its Retina brand to the iPhone, iPad, and MacBook Pro computers, but HiDPI screens remain absent on its MacBook Air, iMac, and external Thunderbolt Display products.
It's not clear whether Apple intends to upgrade its iMac and Thunderbolt Display with Retina technology. It could improve image and text quality, but it also could increase costs, power consumption, and demands on hardware using the displays.
Already, though, other companies offer 4K displays, and the OS X 10.9.3 update brings improved HiDPI support for them too, according to iOS developer Tian Zhang. The better 4K support apparently requires newer Macs because of the processing power required to support the displays at a variety of resolutions.
Without HiDPI support, a monitor could show text and images only at its native resolution. With the Retina support, Apple halves the linear resolution, so a 3,840x2,160 display acts like a conventional HD monitor at 1,920x1080 pixels, with letters and images twice the size as at native resolution but drawn more precisely and clearly. Apple also offers some other choices that can help provide large fonts or intermediate resolutions.
Breaking with recent practices, Apple opened beta testing for OS 10.9.3 to the public, though only in later stages in April and only to people who signed a confidentiality agreement.
The 10.9.3 update also improves VPN (virtual private network) connections and lets you sync calendars and contacts using a USB cable connection between a Mac and an iPhone or iPad. And it includes Safari 7.0.3, for those who hadn't installed that version of the browser when it was first released April 1, to fix some bugs and and improve some security.