OpenGL and OpenGL ES support level depending on GPU chip and version:
Handwrtting recognition system was standard tools in China and Japan, since 1980′s using graphics tablets pads, packaged with specialized software, beside lot of pure keyboard systems. In Europe, we needed to wait until end of 1990′s for handwritting systems in opensource software, and more recently for their democratisation. Those method can also help people without hands to write using foots, mouth or other device that allow to manipulate a more traditionnal writting tool like a pen or a brush.
Kanjipad (english language web site), is probably one of the older (since 1997) handwriting recognition system for Linux, but it is not really active those days.