You will probably want to use
ACAPI_Element_GetElemList
to find the 2d elements to construct the columns from.
I recommend also checking what 2D elements are created when the DWG is merged. Columns might be defined as any of the following:
- Four separate lines
- One to four polylines
- A combination of lines and polylines
- A fill (closed polygon)
- A library part (from an AutoCAD block), which might include the text label
The techniques for finding the elements and extracting relevant geometry will vary according to the element type. It's also possible there may be duplicates, e.g. a fill overlapping 4 bounding lines.
Ralph Wessel BArch
Software Engineer Speckle Systems