In Windows Vista and later, Tablet PC Input Panel is the standard interface for converting handwriting to text in a Windows-based program. It's the method by which tablet pen users enter text into applications that do not include a custom handwriting interface. Using Input Panel, users can insert text into website forms, word processing and e-mail applications, web browsers, and more. Input Panel includes three input areas for entering text: the writing pad, the character pad, and the on-screen keyboard. The writing pad and the character pad convert handwriting into typed text. The on-screen keyboard works just like a standard keyboard except that the user enters text by tapping keys with a tablet pen.
The finer details on how to spec the Input Panel. All these details are very specific so the developers can know how to build the final code. Every pixel matters.