' Name:  View.CalculateAreas
' 
' Title:  Calculates area, acres, square miles, perimeter for polygon shapes.
'        
' Topics:  GeoData
'
' Description:  Calculates area and perimeter for polygon themes.
' If the View has been projected the calculations are in 
' projected units. Otherwise the calculations are in 'native' map units.
' The script processes the list of active themes to calculate 
' area, acres, square miles, and perimeter.  Modified from ESRI sample script
' by Andy Rowan, andy@giscenter.org, 6/13/2001
'
' The script will add the fields Area, Acres, SqMiles and Perimeter to polygon 
' themes if they do not exist. If the fields exist, their values are 
' recalculated. Rerun the script if you change the projection of the view.
'
' Conversion factor for acres and square miles is based on map units in view 
' properties.
'
' Requires:  A View with at least one active theme.  You must have write access
' to the active theme(s).  Map units must be set in view properties.
'
' Self:
'
' Returns:
'
' Version: 3.1

'
' Get the window, make sure it's a view, get its projection (if any).
'
theView = av.GetActiveDoc
if (theView.Is(View).not) then
  msgbox.error("Active window must be a view","")
  return nil
end
thePrj = theView.GetProjection
if (thePrj.IsNull) then
  hasPrj = false
else
  hasPrj = true
end

'
' Get the list of active themes. If there aren't any, let the user know
' and exit.
'
theActivethemeList = theView.GetActivethemes
if (theActivethemeList.Count = 0) then
  MsgBox.Error("No active themes.","")
  return nil
end

' Get view units.  If not set, tell user and exit
'
DistUnits = theView.GetUnits
if (DistUnits = #UNITS_LINEAR_UNKNOWN) then
  msgbox.error("Must set map units in View Properties.","")
  return nil
end

' Set conversion factor for acres ... first use the built-in request to convert
' existing units to square feet, then convert that to acres.
' Then set the conversion for square miles from the built-in request
AcreConversion = units.ConvertArea(1, DistUnits, #UNITS_LINEAR_FEET) * 0.000022956
SqMiConversion = units.ConvertArea(1, DistUnits, #UNITS_LINEAR_MILES)

'
' Loop through the list of active themes. If you can't edit the theme
' inform the user.
'
For Each thetheme in theActivethemeList
  theFTab = thetheme.GetFTab
  if (theFTab.CanEdit.Not) then
    MsgBox.Info("Cannot edit table for theme:"++thetheme.AsString,"")
    Continue
  end
  '
  ' Make the FTAB editable, and find out which type of feature it is.
  '
  theFTab.SetEditable(TRUE)
  theType = theFTab.FindField("shape").GetType
  if (theType = #FIELD_SHAPEPOLY) then
    '
    ' If it's polygonal check for the existence of the fields "Area" and
    ' Perimeter. If they do not exist, create them.
    ' Except for area, ask first before creating them.

    DoAny = MsgBox.YesNo("(Re)Calculate area/perimeter values for"++thetheme.getName+"?", "Calculate", true)
    if (DoAny.not) then
      continue
    end

    'AREA
    if (theFTab.FindField("Area") = nil) then
      theAreaField = Field.Make("Area",#FIELD_DOUBLE,16,3)
      theFTab.AddFields({theAreaField})
    else
      theAreaField = theFTab.FindField("Area")
    end
    
    'ACRE
    if(theFTab.FindField("Acres") = nil)then
      DoAcres = MsgBox.YesNo("Create Acres field in"++thetheme.getName+"?", "Create Field", true)
      if (DoAcres) then
        theAcresField = Field.Make("Acres",#FIELD_DOUBLE,16,3)
        theFTab.AddFields({theAcresField})
      end
    else
      DoAcres = TRUE
      theAcresField = theFTab.FindField("Acres")
    end

    'Sq_Miles
    if(theFTab.FindField("Sq_Miles") = nil)then
      DoSqMi = MsgBox.YesNo("Create Sq_Miles field in"++thetheme.getName+"?", "Create Field", true)
      if (DoSqMi) then
        theSqMiField = Field.Make("Sq_Miles",#FIELD_DOUBLE,16,7)
        theFTab.AddFields({theSqMiField})
      end
    else
      DoSqMi = TRUE
      theSqMiField = theFTab.FindField("Sq_Miles")
    end
    
    
    'PERIMETER
    if (theFTab.FindField("Perimeter") = nil) then
      DoPerim = MsgBox.YesNo("Create Perimeter field in"++thetheme.getName+"?", "Create Field", true)
      if (DoPerim) then
        thePerimeterField = Field.Make("Perimeter",#FIELD_DOUBLE,16,3)
        theFTab.AddFields({thePerimeterField})
      end
    else
      DoPerim = TRUE
      thePerimeterField = theFTab.FindField("Perimeter")
    end
    
    '
    ' Loop through the FTAB and find the projected area and perimeter of each 
    ' shape and set the field values appropriately.
    '
    theShape = theFTab.ReturnValue(theFTab.FindField("shape"),0)

    For Each rec in theFTab      
      theFTab.QueryShape(rec,thePrj,theShape)

      theArea = theShape.ReturnArea
      theFTab.SetValue(theAreaField,rec,theArea)

      if (doAcres) then
        theAcres = theArea*AcreConversion
        theFTab.SetValue(theAcresField,rec,theAcres)
      end

      if (doSqMi) then
        theSqMi = theArea*SqMiConversion
        theFTab.SetValue(theSqMiField,rec,theSqMi)
      end

      if (doPerim) then
        thePerimeter = theShape.ReturnLength
        theFTab.SetValue(thePerimeterField,rec,thePerimeter)
      end
    end

  theFTab.SetEditable(FALSE)
  else
    MsgBox.Info("You must use this script on a polygon theme.",
      "View.CalculateAreas")
    return Nil
  end
end