' Centroid4Poly is Tim's name for it.
' ET.Poly2Cen

' Converts polygons in the active theme to centroid points

' Despite what ArcView's online help says, Polygon.ReturnCenter does NOT
' return the true centroid.  This routine is adapted from O'Rourke,
' Computational Geometry in C.

theTitle = "Convert Polygons to Centroids"
theView = av.GetActiveDoc
theTheme = theView.GetActiveThemes.Get(0)
inFTab = theTheme.GetFTab

' Specify the output shapefile...

fnDefault = FileName.Make("$HOME").MakeTmp("shape","shp")
fnOutput  = FileDialog.Put( fnDefault,"*.shp","Output Shape File" )
if (fnOutput = nil) then exit end

' Multipart option

choicelist = {"Create one centroid point",
              "Create centroid point for each part"}
mpOption = MsgBox.ChoiceAsString(choicelist,"Multipart polygons:",theTitle)
if (mpOption = nil) then exit end

' Do it!

fnOutput.SetExtension("shp")
outFTab = FTab.MakeNew( fnOutput, POINT )
inFields = inFTab.GetFields
newFields = List.Make
for each f in inFields
   if (f.GetName <> "shape") then
      newFields.Add(f.Clone)
   end
end
outFTab.AddFields(newfields)

' Use selected shapes if there are any, otherwise iterate
' through the entire FTab...
'
if (inFTab.GetSelection.Count > 0) then
  colToProcess = inFTab.GetSelection
  nRecs = colToProcess.Count
else
  colToProcess = inFTab
  nRecs = colToProcess.GetNumRecords
end

nullCount = 0
nCount = 0
nRecAdded = 0
mpCount = 0
inSF  = inFTab.FindField("shape")
outSF = outFTab.FindField("shape")
for each r in colToProcess
  val = inFTab.ReturnValue(inSF,r)
   
  if (val.IsNull) then
   nullCount = nullCount + 1
  
  else 
   if (val.Explode.Count > 1) then
      mpCount = mpCount + 1
   end
   if (mpOption = "Create one centroid point") then
      polylist = {val}
   else
      polylist = val.explode
   end
   for each aPolygon in polylist
      ringlist = aPolygon.AsPolyLine.Flip.AsList
      CGx = 0
      CGy = 0
      Areasum2 = 0
      for each plist in ringlist
         n = plist.Count
         for each i in 1..(n-2)
            x0 = plist.Get(0).GetX
            y0 = plist.Get(0).GetY
            x1 = plist.Get(i).GetX
            y1 = plist.Get(i).GetY
            x2 = plist.Get(i+1).GetX
            y2 = plist.Get(i+1).GetY
            Cent3x = x0 + x1 + x2
            Cent3y = y0 + y1 + y2
            A2 = ((x1 - x0) * (y2 - y0)) - ((x2 - x0) * (y1 - y0))
            CGx = CGx + (A2 * Cent3x)
            CGy = CGy + (A2 * Cent3y)
            Areasum2 = Areasum2 + A2
         end
      end
      CGx = CGx / (3 * Areasum2)
      CGy = CGy / (3 * Areasum2)
      p = CGx@CGy

      '**** checks whether p is in polygon, and moves to nearest
      
      if (aPolygon.Contains(p).Not) then
        mindist = 999999
        newp = p
        aPolyListofLists = aPolygon.AsList
        for each plist in aPolyListofLists
          for each pt in plist
            dist = ((pt.GetX - CGx)^2 + (pt.GetY - CGy)^2).sqrt
            if (dist < mindist) then
              mindist = dist
              newp = pt.GetX@pt.GetY
            end
          end
        end
        p = newp
      end

      '**** add record

      nRecNew = outFTab.AddRecord
      outFTab.SetValue(outSF,nRecNew,p)
      for each inF in inFTab.GetFields
         fName = inF.GetName
         if (fName <> "shape") then
            outF = outFTab.FindField(fName)
            val = inFTab.ReturnValue(inF,r)
            outFTab.SetValue(outF,nRecNew,val)
         end
      end
      nRecAdded = nRecAdded + 1
   end
  end
  nCount = nCount + 1
  av.SetStatus((nCount / nRecs) * 100)
end

if (nullCount > 0) then
  MsgBox.Warning("There were " + nullCount.AsString + " null shapes in the folder that " +NL
     + "did not get centroids made.","")
end

av.ClearStatus
av.ClearMsg

theMsg = nCount.AsString++"points created."++NL+
         mpCount.AsString++"multipart polygons processed."
MsgBox.Info(theMsg, theTitle)

if (MsgBox.YesNo("Add shapefile as theme to a view?",
  theTitle, true).Not) then
  exit
end

' Create a list of views and allow the user to choose which view to
' add the new theme to...
lstViews = {}
for each d in av.GetProject.GetDocs
  if (d.Is(View)) then
    lstViews.Add( d )
  end
end
lstViews.Add("<New View>")

vweAddTo = MsgBox.ListAsString( lstViews,"Add Theme to:",
  "Convert Polygon to Point" )

' Get the specified view, make the theme, and add it...
if (vweAddTo <> nil) then
  if (vweAddTo = "<New View>") then
    vweAddTo = View.Make
    vweAddTo.GetWin.Open
  end
  thmNew = FTheme.Make(outFTab)
  vweAddTo.AddTheme( thmNew )
  vweAddTo.GetWin.Activate
end