void draw_empty_square (cairo_t *, uint32_t, uint32_t);
void draw_non_connectable_indicator (cairo_t *, uint32_t, uint32_t);
std::list<PortMatrixNode> nodes_on_line (int, int, int, int) const;
void draw_empty_square (cairo_t *, uint32_t, uint32_t);
void draw_non_connectable_indicator (cairo_t *, uint32_t, uint32_t);
std::list<PortMatrixNode> nodes_on_line (int, int, int, int) const;