sclass JPaintTool > MetaWithChangeListeners is Swingable, AutoCloseable {
  settableWithVar File autoPersistFile;
  settableWithVar double autoPersistInterval = 10.0;
  settableWithVar Color brushColor = Color.black;
  
  transient settableWithChange volatile bool dirty;
  transient gettable BufferedImage image;
  transient ImageSurface imageSurface;
  transient bool autoPersistInstalled;
  transient ReliableSingleThread rstPersist = new(r _persist);
  transient JPanel buttons;
  transient ImageSurfaceScribbleTool scribbler;
  transient JComboBox<WidthAndHeight> cbImageSize;
  transient settableWithVar S status;
  transient new ButtonGroup colorButtonGroup;
  
  transient simplyCached void init() {
    imageSurface = makeImageSurface();
    
    cbImageSize = jTypedComboBox(imageSizes());
    main onChange(cbImageSize, l1 setImageSize);

    printVars("JPaintTool.init", +image, +autoPersistFile);
    if (image == null) {
      setImage(makeNewImage());
      
      if (autoPersistFile != null) {
        pcall {
          var img = loadImage2(autoPersistFile);
          if (img != null) {
            setImage(img);
            print("Image loaded");
          }
        }
                      
        if (!autoPersistInstalled) {
          set autoPersistInstalled;
          awtEvery(imageSurface, autoPersistInterval, rstPersist);
          bindToComponent(imageSurface, null, rstPersist);
        }
      }

    }
  }
  
  BufferedImage makeNewImage() {
    ret main newImage(defaultImageSize());
  }
  
  WidthAndHeight defaultImageSize() { ret getSelected(cbImageSize); }
  
  public transient simplyCached JComponent visualize() {
    init();
    var filePathLabel = new JFilePathLabel(autoPersistFile).nameOnly();
    varAutoPersistFile().onChange(file -> filePathLabel.setFile(file));
    
    ret withTopMargin(northCenterAndSouthWithMargin(
      buttons = jcenteredline(flattenToList(
        jbutton("New image", rThread newImage),
        withLabel("Size:", cbImageSize),
        map colorSelectButton(colors())
      )),
      jscroll_center_borderless(imageSurface),
      centerAndEast(
        jVarLabel(varStatus()),
        autoPersistFile == null ? jpanel()
          : withLeftMargin(withLabel("File", filePathLabel.visualize()))
      )
    ));
  }
  
  void setImage(BufferedImage image) {
    this.image = image;
    imageSurface.setImage(image);
    revalidate(getParent(imageSurface)); // XXX
  }

  transient swappable ImageSurface makeImageSurface() {  
    var is = pixelatedImageSurface();
    //is.setAutoZoomToDisplay(true);
    //is.specialPurposed = true;
    is.zoomable(false);
    is.removeAllTools();
    scribbler = new ImageSurfaceScribbleTool(is);
    scribbler.onPainted(-> { set dirty; });
    varBrushColor().onChangeAndNow(color -> scribbler.setColor(color));
    
    ret is;
  }
  
  void _persist {
    if (autoPersistFile != null && dirty) {
      dirty = false;
      savePNGVerbose(autoPersistFile, image);
    }
  }
  
  void newImage() ctex {
    close(); // persist
    //if (dirty && !swingConfirm(imageSurface, "Discard image")) ret;
    
    var file = createAutoPersistFile();
    print("Created auto persist file: " + f2s(file));
    autoPersistFile(file);
    setImage(makeNewImage());
    dirty = false;
  }
  
  // swap to make a new file every time user clicks "New image"
  swappable File createAutoPersistFile() { ret autoPersistFile(); }
  
  JToggleButton colorSelectButton(Color color) {
    var btn = jImageToggleButton(main newImage(16, color),
      "Select color to draw with", -> setBrushColor(color),
      eq(brushColor(), color));
    ret addToButtonGroup(colorButtonGroup, btn);
  }
  
  L<Color> colors() {
    ret colorPaletteByBits(1); // 8 primary colors
  }
  
  L<WidthAndHeight> imageSizes() {
    ret mapLL sixteenToNine_p(
      240, 360, 480, 720
    );
  }
  
  void setImageSize(WidthAndHeight size) {
    if (!sameSize(getImage(), size))
      newImage();
  }
  
  close {
    rstPersist.triggerAndWait();
  }
}