procedure CopyGMDXIniFiles;
{ procedure that enters the necessary items in the "Paths" portion of DeusEx.ini for GMDX.  The typical INI calls
  do not work for the "Paths" portion since duplicate names are not typical INI standard. }
  var
    sstrings: TStringList;
    ndx1, ndx2: integer;
  begin
    sstrings := TStringList.Create;
    try
      sstrings.LoadFromFile(ExpandConstant('{app}\gmdx\System\gmdx.ini'));
      // system line
      ndx1 := sstrings.IndexOf('Paths=..\GMDX\System\*.u'); // locate target line.
      if ndx1 > -1 then
        sstrings.Delete(ndx1);  // if already exists, delete it.
      ndx1 := sstrings.IndexOf('Paths=..\System\*.u');  // find systems line - will always exist if DeusEx.ini isn't borked.
      if ndx1 > -1 then  // if it exists.
        begin
          ndx2 := sstrings.IndexOf('Paths=..\HDTP\System\*.u');  // look for HDTP system line.
          if ndx2 > -1 then
            sstrings.Insert(ndx2, 'Paths=..\GMDX\System\*.u')  // if found, put the line before HDTP line
          else
            sstrings.Insert(ndx1, 'Paths=..\GMDX\System\*.u');  // if not, put it after the system line.
        end;
{...}
      sstrings.SaveToFile(ExpandConstant('{app}\gmdx\System\gmdx.ini'));
    finally
      sstrings.Free;
    end;
  end;

Paths=..\GMDX\System\*.u
Paths=..\HDTP\System\*.u
Paths=..\System\*.u

Paths=..\GMDX\System\*.u
Paths=..\System\*.u

function FormatPathString(str : String) : String;
var
    firstThreeChars       : String;
    charsAfterFirstThree  : String;
    tempString  : String;
    finalString  : String;
    dividerPosition   : Integer;
begin

  firstThreeChars := Copy(str, 0, 3);                //First copy the first thee character which we want to keep
  charsAfterFirstThree := Copy(str,4,Length(str));   //copy the rest of the string into a new variable
  dividerPosition := Pos('\', charsAfterFirstThree); //find the position of the following '\'
  tempString := Copy(charsAfterFirstThree,dividerPosition+1,Length(charsAfterFirstThree)-dividerPosition);            //Take everything after the position of '\' (dividerPosition+1) and copy it into a temporary string
  finalString := firstThreeChars+tempString;         //put your first three characters and your temporary string together
  Result := finalString;                             //return your final string
end;

procedure AppendKey(const FileName, Section, KeyName, KeyValue: string);
var
  S: string;
  I: Integer;
  CurLine: string;
  LineIdx: Integer;
  SnFound: Boolean;
  Strings: TStringList;
begin
  Strings := TStringList.Create;
  try
    S := Format('[%s]', [Section]);

    Strings.LoadFromFile(FileName);
    SnFound := False;
    LineIdx := Strings.Count;

    for I := Strings.Count - 1 downto 0 do
    begin
      CurLine := Trim(Strings[I]);
      // if the iterated line is a section, then...
      if (Length(CurLine) > 2) and (CurLine[1] = '[') and (CurLine[Length(CurLine)] = ']') then
      begin
        // if the iterated line is the section we are looking for, then...
        if CompareText(S, CurLine) = 0 then
        begin
          SnFound := True;
          Break;
        end;
      end
      else
        if CurLine = 'Paths=' + FormatPathString(KeyValue) then
          LineIdx := I;
    end;

    if not SnFound then
    begin
      Strings.Add(S);
      Strings.Add(Format('%s=%s', [KeyName, KeyValue]));
    end
    else
      Strings.Insert(LineIdx, Format('%s=%s', [KeyName, KeyValue]));

    Strings.SaveToFile(FileName);
  finally
    Strings.Free;
  end;
end;

procedure CurStepChanged(CurStep: TSetupStep);
Begin
if (CurStep=ssDone) and IsComponentSelected('NV') then
  begin
      AppendKey(ExpandConstant('{app}\System\DeusEx.ini'), 'Core.System', 'Paths', '..\New Vision\Maps\*.dx');
      AppendKey(ExpandConstant('{app}\System\DeusEx.ini'), 'Core.System', 'Paths', '..\New Vision\Textures\*.utx');
  end;
if (CurStep=ssDone) and IsComponentSelected('HDTP') then
  begin
      AppendKey(ExpandConstant('{app}\System\DeusEx.ini'), 'Core.System', 'Paths', '..\HDTP\System\*.u');
      AppendKey(ExpandConstant('{app}\System\DeusEx.ini'), 'Core.System', 'Paths', '..\HDTP\Textures\*.utx');
  end;
if (CurStep=ssDone) and IsComponentSelected('NV') and IsComponentSelected('HDTP') then
  begin
      AppendKey(ExpandConstant('{app}\System\hdtp.ini'), 'Core.System', 'Paths', '..\New Vision\Maps\*.dx');
      AppendKey(ExpandConstant('{app}\System\hdtp.ini'), 'Core.System', 'Paths', '..\New Vision\Textures\*.utx');
  end;
End;