//no property keyword yet.. just tryin to get the logic right first
type
  TFoo = record
    FData: array of Int32;
    FWidth:Int32;
  end;

procedure TFoo.Prop(x,y:Int32; value:Int32);
begin
  FData[y*FWidth+x] := value;
end;

function TFoo.Prop(x,y:Int32): Int32; overload;
begin                               //+0 because I am having wicked issues with setting correct dest
  Result := FData[y*FWidth+x] + 0;  //yep.. that's right, I changed how array indexing is parsed - it's ugly atm.
end;

var
  foo:TFoo;
begin
  SetLength(foo.FData, 20*20);
  foo.FWidth := 20;

  foo.Prop[10,10] := 99;
  WriteLn(foo.Prop[10,10]);
end.

>>> 99