why I can't read point data from polyline

taishengchen

I write an ATL project like logomarkersymbol. I want to read polyline data in Draw function , I use IPointCollectionPtr to read, but failed, the pointcollection is empty. Why???

my code is :

IPolylinePtr spPolyline(Geometry);
           IGeometryCollectionPtr spGeometryCollection(spPolyline);

if(NULL == spGeometryCollection)
  return E_FAIL;

long nGeos=0;
spGeometryCollection->get_GeometryCount(&nGeos);

for (i=0;i<nGeos;i++)
{
  IGeometryPtr spGeometry;
  spGeometryCollection->get_Geometry(i, &spGeometry);
  IPointCollectionPtr spCollection(spGeometry);

  long nPoints=0;
  nPoints = spPointCollection->get_PointCount(&nPoints);

                      //spPolyline, spGeometry and spPointCollection has values, but npoint is empty. why???
                      ??????  
             }

ArunIndugula

I've only looked at this for a few minutes, but it looks like you have two bugs here:



...

IPointCollectionPtr spCollection(spGeometry);   // BUG 1: this variable needs to be called "spPointCollection" to match the next use

long nPoints=0;
nPoints = spPointCollection->get_PointCount(&nPoints);  // BUG 2: you are returning your HRESULT into your nPoints variable

...


So here's how I would fix this:

...

IPointCollectionPtr spPointCollection(spGeometry);

long nPoints=0;
HRESULT hr = spPointCollection->get_PointCount(&nPoints);

...

Keep in mind, the reason your points kept returning "0" is because that is the HRESULT code for "OK".  I tested these changes out and they seem to give me good results.

-Sigma3 Engineer