+ void draw_association_indicator (cairo_t *, uint32_t, uint32_t, double p = 1);
+ void draw_empty_square (cairo_t *, uint32_t, uint32_t);
+ void draw_unknown_indicator (cairo_t *, uint32_t, uint32_t);
+ std::list<PortMatrixNode> nodes_on_line (int, int, int, int) const;
+ PortMatrixNode::State get_association (PortMatrixNode) const;
+ void set_association (PortMatrixNode, bool);
+ bool toggle_state (PortMatrixNode::State) const;