With Surface Pro lineup, Microsoft is already embracing the Pen and Ink input platform. Developers need to use special APIs such as Windows Ink API or the Wintab driver set to enable pen and inking support in their apps. Apps that you have downloaded from the Windows Store like Sketchbook Express, Sketchable, Fresh Paint, and even OneNote will give you subtle brush strokes out of the box and they make use of Windows Ink API.
With Windows 10 Input Platform, Microsoft is introducing a new inking platform called DirectInk. DirectInk is supported for all universal apps in Windows 10. These new APIs will enable developers build highly rich inking experience like OneNote and also simple apps that support inking. Microsoft is also helping OEMs to build compatible active pen hardware that will work with Windows 10 devices.