code: function (checker) {
              if (isFunction(checker)) {
                  this.getRect = checker;
  
                  return this;
              }
  
              if (checker === null) {
                  delete this.options.getRect;
  
                  return this;
              }
  
              return this.getRect;
          }
docs: /*\
  Interactable.rectChecker
  [ method ]
  
  Returns or sets the function used to calculate the interactable's
  element's rectangle
  
  - checker (function) #optional A function which returns this Interactable's bounding rectangle. See @Interactable.getRect
  = (function | object) The checker function or this Interactable
  \