FFT window.

enum TFFTWindow {
  fwRectangular = 1,
  fwHamming,
  fwHann,
  fwCosine,
  fwLanczos,
  fwBartlett,
  fwTriangular,
  fwGauss,
  fwBartlettHann,
  fwBlackman,
  fwNuttall,
  fwBlackmanHarris,
  fwBlackmanNuttall,
  fwFlatTop
};