simple linux cam

Handle(Geom_Line) line = Handle(Geom_Line)::DownCast(c);
     qDebug() << "cutCurve (line):" << first << " | " << last << " <> " << orientation;
     double dx  = p1.X() - p0.X();
     double dy  = p1.Y() - p0.Y();
     double gf  = dy / dx;
     double cf  = rMaster / sqrt(1 + gf * gf);
     double dr  = sqrt(dx * dx + dy * dy);
     double D   = p0.X() * p1.Y() - p1.X() * p0.Y();
     double res = rMaster * rMaster * dr * dr - D * D;
     double sig = dy < 0 ? -1 : 1;
     double cx0 = cf * gf;
     double cy0 = -cf;
     double cx1 = -cx0;
     double cy1 = -cy0;
     double x0  = ( D * dy + sig * dx * sqrt(res)) / (dr * dr);
     double x1  = ( D * dy - sig * dx * sqrt(res)) / (dr * dr);
     double y0  = (-D * dx + abs(dy)  * sqrt(res)) / (dr * dr);
     double y1  = (-D * dx + abs(dy)  * sqrt(res)) / (dr * dr);
     double col = first + (last - first) / 2;

     if (res <= 0) qDebug() << "OUPS - fine calculations means no cutpoints?!?";
     qDebug() << "cutpoints: " << cx0 << " / " << cy0
              <<   "   and   " << cx1 << " / " << cy1;
     qDebug() << "alt cp: "  << x0 << " / " << y0
              << "   and   " << x1 << " / " << y1;

//     Core().view3D()->createAxisCross({cx0, cy0, 0}, 2, nullptr, Quantity_NOC_BLACK);
//     Core().view3D()->createAxisCross({cx1, cy1, 0}, 2, nullptr, Quantity_NOC_WHITE);
     Core().view3D()->createAxisCross({x0, y0, 0}, 2, nullptr, Quantity_NOC_BLACK);
     Core().view3D()->createAxisCross({x1, y1, 0}, 2, nullptr, Quantity_NOC_WHITE);

//     double param0 = ElCLib::Parameter(line->Lin(), {cx0, cy0, p0.Z()});
//     double param1 = ElCLib::Parameter(line->Lin(), {cx1, cy1, p0.Z()});
     double param0 = ElCLib::Parameter(line->Lin(), {x0, y0, p0.Z()});
     double param1 = ElCLib::Parameter(line->Lin(), {x1, y1, p0.Z()});

     if (param0 >= first && param0 <= last) {
        qDebug() << "<<< first cutpoint is part of line segment ==> "
                 << first << " <> "  << param0 << " <> " << last << "orientation:" << orientation;
        if (param0 < col) {
           qDebug() << "\tsecond part is part of interest";
           edge = BRepBuilderAPI_MakeEdge(c, {x0, y0, p0.Z()}, p1);
           }
        else {
           qDebug() << "\tfirst part is part of interest";
           edge = BRepBuilderAPI_MakeEdge(c, p0, {x0, y0, p0.Z()});
           }
        }
     else if (param1 >= first && param1 <= last) {
        qDebug() << ">>> second cutpoint is part of line segment ==> "
                 << first << " <> "  << param1 << " <> " << last << "orientation:" << orientation;
        if (param1 < col) {
           qDebug() << "\tsecond part is part of interest";
           edge = BRepBuilderAPI_MakeEdge(c, {x1, y1, p0.Z()}, p1);
           }
        else {
           qDebug() << "\tfirst part is part of interest";
           edge = BRepBuilderAPI_MakeEdge(c, p0, {x1, y1, p0.Z()});
           }
        }
     else {
        qDebug() << "?!?!? - none of the calculated cutpoints is inside of line parameters?!?"
                 << first << " <> " << param0 << "|" << param1 << last;
        edge = BRepBuilderAPI_MakeEdge(c, first, last);
        }
     }