/// return x,y of given position relative to the inset's baseline
void cursorPos(BufferView const & bv, CursorSlice const & sl,
bool boundary, int & x, int & y) const;
/// return x,y of given position relative to the inset's baseline
void cursorPos(BufferView const & bv, CursorSlice const & sl,
bool boundary, int & x, int & y) const;