VDI is responsible for drawing primitives on a display. Things like lines, boxes, circles and text are typical things for a VDI library.

oVDIsis is a library that provides the system calls for these primitives, which together with the library in oAESis provides everything needed for the server in oAESis to output nice windows, menus and buttons.

There are several output targets for this part, where oFBis is one of them.

oVDIsis is part of the OSIS project.