int xm() const { return xo_ + dim_.wid / 2; }
/// access to cached y coordinate of mid point of last drawing
int ym() const { return yo_ + (dim_.des - dim_.asc) / 2; }
+ ///
+ bool contains(int x, int y) const;
/// write access to coordinate;
void setXY(int x, int y) const;
/// returns x coordinate of given position in the array