Constructing a Variant from a List of Points

AutoCAD Visual LISP

Constructing a Variant from a List of Points

So far, the data in the polypoints variable is in a list format suitable for many AutoLISP calls. However, the data is to be supplied as an input parameter to an ActiveX call that expects a variant array of doubles. You can use another utility function to make the required conversion from list to variant:

(defun gp:list->variantArray (ptsList / arraySpace sArray)
  ; allocate space for an array of 2d points stored as doubles
  (setq arraySpace (vlax-make-safearray
              vlax-vbdouble ; element type
              (cons 0
                    (- (length ptsList) 1)
                    ) ; array dimension
  (setq sArray (vlax-safearray-fill arraySpace ptsList))
  ; return array variant
  (vlax-make-variant sArray)

The following actions take place in gp:list->variantArray:

  • The vlax-make-safearray function is called to allocate an array of doubles (vlax-vbdouble). The vlax-make-safearray function also requires you to specify the lower and upper index boundaries of the array. In gp:list->variantArray, the call to vlax-make-safearray specifies a start index of 0 and sets the upper limit to one less than the number of elements passed to it (ptsList).
  • The vlax-safearray-fill function is called to populate the array with the elements in the point list.
  • The vlax-make-variant is called to convert the safearray into a variant. As the last function call in gp:list->variantArray, the return value is passed to the calling function.

The following is an example of a function call that invokes gp:list->variantArray to convert a list to a variant array of doubles:

; data conversion from list to variant
(setq VLADataPts (gp:list->variantArray polypoints))