sclass G22SnPSelector > MetaWithChangeListeners is Swingable {
  settable new SnPSettings settings;
  
  // show powers of two in colors selector or all numbers?
  settableWithVar bool powerOfTwoColors = false;
  
  // show powers of two in pixelRows selector or all numbers?
  settableWithVar bool powerOfTwoPixelRows = true;
  
  settable int maxPixelRows = 512;
  
  settableWithVar bool allowDecolorizerSelection;
  settableWithVar bool showDecolorizerSelection;
  
  JLabel lblColors;
  SingleComponentPanel scpDecolorizer = scp();
  
  *() {}
  *(SnPSettings *settings) {}
  
  SnPSettings get() { ret settings; }

  cachedVisualize {
    var colors = jListSpinner(colorsList(), settings.colors);
    main onChange(colors, -> {
      settings.colors = intFromSpinner(colors);
      change();
    });
    
    varPowerOfTwoColors().onChange(->
      spinnerSetNumberList(colors, colorsList());

    swing {
      var menuItem = jLiveValueCheckBoxMenuItem("Only show powers of two", varPowerOfTwoColors());
      new JPopupMenu menu;
      menu.add(menuItem);
      colors.setComponentPopupMenu(menu);
    }
    
    var pixelRows = jListSpinner(pixelRowsList(), settings.pixelRows);
    main onChange(pixelRows, -> {
      settings.pixelRows = intFromSpinner(pixelRows);
      change();
    });
    
    varPowerOfTwoPixelRows().onChange(->
      spinnerSetNumberList(pixelRows, pixelRowsList());

    swing {
      var menuItem = jLiveValueCheckBoxMenuItem("Only show powers of two", varPowerOfTwoPixelRows());
      new JPopupMenu menu;
      menu.add(menuItem);
      pixelRows.setComponentPopupMenu(menu);
    }
    
    lblColors = jSimpleLabel(" colors ");
    bindChangeListenerToComponent(this, lblColors,
      -> toolTip(lblColors, makeToolTip()));
    
    L controls = ll(
      colors,
      lblColors,
      scpDecolorizer,
      jSimpleLabel("@ "),
      pixelRows,
      jlabel(" p"));
      
    if (allowDecolorizerSelection) {
      varShowDecolorizerSelection().onChangeAndNow(l0 updateDecolorizerView);
      controls.add(horizontalStrut(3));
      controls.add(jPopDownButton_noText(
        jLiveValueCheckBoxMenuItem("Select channel", varShowDecolorizerSelection())
      ));
    }
      
    var vis = hstack(controls);
    bindChangeListenerToComponent(settings, vis, l0 change);
    ret vis;
  }
  
  L<Int> colorsList() {
    ret powerOfTwoColors
      ? powersOfTwoUpTo(2, 256)
      : virtualCountList_incl(2, 256);
  }
  
  L<Int> pixelRowsList() {
    ret powerOfTwoPixelRows
      ? powersOfTwoUpTo(maxPixelRows)
      : virtualCountList_incl(1, maxPixelRows);
  }
  
  S makeToolTip() {
    long pixels = area(sixteenToNine_p(settings.pixelRows));
    int colorBits = numberOfBitsNeededToRepresentNOptions(settings.colors);
    int bytes = iceil_div(pixels*colorBits, 8);
    ret "Information per frame: " + nBytes(bytes) +" (assuming a 16:9 aspect ratio)";
  }
  
  L<Decolorizer> decolorizerList() {
    ret ll(
      new Decolorizer.Simple,
      new Decolorizer.Red,
      new Decolorizer.Green,
      new Decolorizer.Blue
    );
  }
  
  void updateDecolorizerView {
    if (!showDecolorizerSelection) {
      scpDecolorizer.clear();
      settings.decolorizer(null);
    } else {
      if (settings.decolorizer == null)
        settings.decolorizer(new Decolorizer.Simple);
      scpDecolorizer.set(hstack(
        jlabel("from channel "),
        bindComboBoxToVar(settings.varDecolorizer(),
          jTypedComboBox(decolorizerList())),
        horizontalStrut(3)
      ));
    }
  }
}