Re: COM/Automation: how do I pass an array to a variant parameter in LWW ?

At 21:53 18/10/2006, Martti Halminen wrote:

>I'm trying to use LWW 4.4.6 for programming AutoCAD 2006 through ActiveX,
>  and got stuck when trying to send a Lisp array to it in a parameter
>expecting a variant.
>I can't make any sense of the documents, and no example code I have found
>shows LWW operation with variants
>  containing arrays.
>
>Neither the array as such nor anything produced by com:make-lisp-variant
>that I have tried works.
>
>The receiving function definition in the type library as IDL:
>
>         [id(0x0000000e), helpstring("Append loops to the hatch"),
>helpcontext(0x00010117)]
>         HRESULT AppendOuterLoop([in] VARIANT ObjectArray);
>
>
>
>In VBA this can be used directly with an array of objects:
>     ' Create the associative Hatch object
>     Set hatchObj = ThisDrawing.ModelSpace.AddHatch(PatternType,
>patternName, bAssociativity)
>
>     ' Create the outer loop for the hatch.
>     ' An arc and a line are used to create a closed loop.
>     Dim outerLoop(0 To 1) As AcadEntity
>     Dim center(0 To 2) As Double
>     Dim radius As Double
>     Dim startAngle As Double
>     Dim endAngle As Double
>     center(0) = 5: center(1) = 3: center(2) = 0
>     radius = 1
>     startAngle = 0
>     endAngle = 3.141592
>     Set outerLoop(0) = ThisDrawing.ModelSpace.AddArc(center, radius,
>startAngle, endAngle)
>     Set outerLoop(1) =
>ThisDrawing.ModelSpace.AddLine(outerLoop(0).startPoint,
>outerLoop(0).endPoint)
>
>     ' Append the outer loop to the hatch object, and display the hatch
>     hatchObj.AppendOuterLoop (outerLoop)
>     hatchObj.Evaluate
>
>
>
>So, how am I supposed to call invoke-dispatch-method with an array of
>i-dispatch objects?

Hi,

I would expect something like this to work (completely untested btw) ...

(defun add-hatch (model-space pattern-type pattern-name b-associativity)
   (let((center (vector 5.0 3.0 0.0))
        (radius 1.0)
        (start-angle 0.0)
        (end-angle 3.141592))
     (com:with-temp-interface
         (hatch)
         (com:invoke-dispatch-method model-space "AddHatch" pattern-type 
pattern-name b-associativity)
       (com:with-temp-interface
           (arc-entity)
           (com:invoke-dispatch-method model-space "AddArc" center radius 
start-angle end-angle)
         (let ((start-point (com:invoke-dispatch-get-property arc-entity 
"startPoint"))
               (end-point (com:invoke-dispatch-get-property arc-entity 
"endPoint")))
           (com:with-temp-interface
               (line-entity)
               (com:invoke-dispatch-method model-space "AddLine" 
start-point end-point)
             (com:invoke-dispatch-method hatch "AppendOuterLoop" (vector 
arc-entity line-entity))
             (com:invoke-dispatch-method hatch "Evaluate")))))))

What errors do you get ?

The LWW doc is not explicit about how it handles types inside arrays:

http://www.lispworks.com/documentation/lw50/COM/html/com-95.htm#84037

But as it can handle conversion between  com:com-interface and IDispatch*
(VT_DISPATCH) as top level arguments I would expect it to work when these
values are in an array.  LWW should create a VARIANT with vt set to VT_ARRAY
| VT_DISPATCH.  This should work with the AppendOuterLoop method.

If you want or need to try creating a variant explicitly then I think you 
need to do
(make-lisp-variant '(:array :dispatch :dispatch) (vector arc-entity 
line-entity))
rather than just (vector arc-entity line-entity) in the code above.

(BTW I am guessing that startPoint and endPoint are properties that return
an array of floats. If they return IDispatch interfaces then they should be
wrapped in com:with-temp-interface or explicitly released. If they are
methods not properties then use com:invoke-dispatch-method - to state the
obvious ;-)

HTH

paulm