[quote user="Nabil Kherouf"]I'm interested in the clip boundary of the reference file[/quote]
Why not get that from the ReferenceInfo of the attachment?
#include <msreffile.fdf>
#include <refernce.h>
ReferenceFile* pInfo = mdlRefFile_getInfo (oAttachment);
int nVertices = pInfo->clip.clip_vertices;
DPoint2d* clipPoints = pInfo->clip.clipP;
Note that the clip points are 2D.