rem: points[i].x += x; points[i].y += y;
add: points[i].x = x + points[i].x; points[i].y = y - points[i].y;
context: gerbv_draw_prim20(GdkPixmap *pixmap, GdkGC *gc, stack_t *s, int scale,		  gint x, gint y){    const int linewidth_idx = 1;    const int start_x_idx = 2;    const int start_y_idx = 3;    const int end_x_idx = 4;    const int end_y_idx = 5;    const int rotation_idx = 6;    const int nuf_points = 2;    GdkGC *local_gc = gdk_gc_new(pixmap);    GdkPoint points[nuf_points];    int i;    gdk_gc_copy(local_gc, gc);    gdk_gc_set_line_attributes(local_gc, 			       (int)round(scale * s->stack[linewidth_idx]),			       GDK_LINE_SOLID, 			       GDK_CAP_BUTT, 			       GDK_JOIN_MITER);    points[0].x = (s->stack[start_x_idx] * scale);    points[0].y = (s->stack[start_y_idx] * scale);    points[1].x = (s->stack[end_x_idx] * scale);    points[1].y = (s->stack[end_y_idx] * scale);    for (i = 0; i < nuf_points; i++) {	points[i] = rotate_point(points[i], s->stack[rotation_idx]);	points[i].x += x;	points[i].y += y;    }    gdk_draw_line(pixmap, local_gc, 		  points[0].x, points[0].y, 		  points[1].x, points[1].y);        gdk_gc_unref(local_gc);    return;} /* gerbv_draw_prim20 */