src/classes/sigma.classes.edgequad.js
function(r, llc) {
      return {
        x: llc.x - r.x1 + r.x2,
        y: llc.y - r.y1 + r.y2
      };
    }
function(r, llc) {
      return {
        x: llc.x - r.x1 + r.x2,
        y: llc.y - r.y1 + r.y2
      };
    }
function ( r , llc ) { return { x : llc . x - r . x1 + r . x2 , y : llc . y - r . y1 + r . y2 } ; }
Get coordinates of a rectangle's lower right corner from its top points
and its lower left corner.

@param  {object} A rectangle defined by two points (x1, y1) and (x2, y2).
@param  {object} A corner's coordinates (x, y).
@return {object} Coordinates of the corner (x, y).
Get coordinates of a rectangle s lower right corner from its top points and its lower left corner .