ggiGetRayPos - Find out where the raster beam is
int ggiGetRayPos(ggi_visual_t vis, int32_t* x, int32_t* y);
Though currently only implemented via matroxfb, this function will
retrieve the current position of the raster beam on a display that uses
a cathode ray tube, or resembles such internally. Because it has not
been implemented and put into widespread use, there may be API
fluctuation as to exactly what units x, y are in, especially on
displays using doublescanning modes. In addition to numerical values,
the following values can be returned in either dimension: GGI_RP_BORDER
means the raster is in the border of the screen; GGI_RP_BLANK means the
raster is past the border and is turned off; GGI_RP_SYNC means the
raster is retracing to the top of the screen.
0 for OK, otherwise an ggi-error(3) code.