Apple has seeded a third beta of OS X Yosemite 10.10.3 to developers for testing, bringing support for the Force Touch trackpad.
Force Touch developer APIs
The new MacBook Pro (Retina, 13-inch, Early 2015) supports new Force Touch trackpad features. You can find out more about Force Touch trackpad features here: https://support.apple.com/kb/HT204352
This beta of OS X 10.10.3 contains new developer APIs that work with the Force Touch trackpad in the new MacBook Pro (Retina, 13-inch, Early 2015) to allow a new level of interactivity and control within your apps.
● Force click. Apps can have any button, control, or region on the screen respond to a press of stronger pressure. This Force click can provide a shortcut to additional functionality within the app.
● Accelerators. Pressure sensitivity in the trackpad enables apps to give users greater control. For instance the fast-forward button in media playback can speed up as pressure increases.
● Pressure sensitivity. Drawing and other creative apps can take advantage of the pressure-sensing capabilities of the trackpad to make lines thicker or give the brush a changing style.
● Drag and Drop. Apps can add the springLoaded property to their controls so they can react to a Force click gesture while in the middle of performing a drag, for instance to immediately open a new target for the drop.