Field hw is enclosed in a Delphi compiler directive. This means for Linux, graphics output is not available yet. Field hw is a handle to the little window where graphics are displayed, as in Figure 12. This handle has to be initialized and freed. Using hw, a Canvas object has to be instantiated and freed. Object Canvas provides then lot of painting methods, like LineTo and Ellipse. Please refer to source code of the pi.dll plugin for more details. An even more advanced plugin with 3D graphics implemented in OpenGL  is teapot.dll.