' Written by Timothy S. Thomas.
' Programming began 12/23/99.
' Last update was 12/23/99.

' ***********************************************************************
' This script subtracts one theme from another
' ***********************************************************************

' Beginning program
theProject = av.GetProject
theView = av.GetActiveDoc

'Choose themes
theThemeList = theView.GetThemes
mainTheme = MsgBox.ChoiceAsString(theThemeList,"Select theme to subtract from",
            "Select theme")
subTheme = MsgBox.ChoiceAsString(theThemeList,"Select theme to use for subtracting",
            "Select theme")
mainFTab = mainTheme.GetFTab
subFTab = subTheme.GetFTab
mainFTab.SetEditable(True)
subFTab.SetEditable(True)
mainshapeField = mainFTab.FindField("Shape")
subshapeField = subFTab.FindField("Shape")
            
' Get filename for new shapefile, and make new shapefile
FTabFN = mainFTab.GetSrcName.GetFileName
baseString = FTabFN.GetBaseName
extString = FTabFN.GetExtension
newString = FTabFN.AsString.Substitute(baseString,"")
new2String = baseString.Substitute(extString,"dbf")
outFN = FileDialog.Put((newString + "Subtracted " + new2String).AsFileName,
          "*.shp","Output Shapefile")
outFN.SetExtension("shp")
outFTab = FTab.MakeNew(outFN,POLYGON)
outshapeField = outFTab.FindField("Shape")

' Clone fields for outFTab
inFields = mainFTab.GetFields
newFields = List.Make
for each f in inFields
   if (f.GetName <> "shape") then
      newFields.Add(f.Clone)
   end
end
outFTab.AddFields(newfields)

'Merging subtraction features into one feature
tempfield={Field.Make ("c", #FIELD_SHORT, 2, 0)}
subFTab.AddFields( tempfield )
cField=subFTab.findfield("c")
sub2FN = "$HOME".AsFileName.MakeTmp("tmp","shp")
sub2FTab = subFTab.Summarize(sub2FN,SHAPE,cField,{subshapeField},{#VTAB_SUMMARY_AVG})
sub2shapeField = sub2FTab.FindField("Shape")
' Create a spatial index to increase speed
sub2FTab.CreateIndex(sub2shapeField)
' Add theme to table
sub2Theme = FTheme.Make(sub2FTab)
theView.AddTheme(sub2Theme)
sub2FTab.SetEditable(True)
' Get poly shape for subtraction
subPoly = sub2FTab.ReturnValue(sub2shapeField,0)

' Show message
av.ShowMsg("Do subtraction")
av.ShowStopButton
numrecs = mainFTab.GetNumRecords

' Do subtraction, and write output
for each r in mainFTab
  mainPoly = mainFTab.ReturnValue(mainshapeField,r).ReturnDifference(subPoly)
  ' Output result
  newrec = outFTab.AddRecord
  outFTab.SetValue(outshapeField,newrec,mainPoly)
  for each fld in mainFTab.GetFields
    fldName = fld.GetName
    if (fldName <> "shape") then
      outfld = outFTab.FindField(fldName)
      val = mainFTab.ReturnValue(fld,r)
      outFTab.SetValue(outfld,newrec,val)
    end
  end
  av.SetStatus((r+1) * 100 / numrecs)
end

' Clears message
av.ClearMsg

' Add to view
if (MsgBox.YesNo("Add shapefile to view?","", true)) then
  outTheme = FTheme.Make(outFTab)
  theView.AddTheme(outTheme)
  theView.GetWin.Activate
end