sclass JFFMPEGVideoPlayer is Swingable {
  ImageSurface imageSurface = imageSurface();
  JPanel buttons = rightAlignedLine();
  
  ImageStreamFromVideoFile stream;
  long playStartTime;
  
  {
    buttons.add(jbutton("Open video...", rThread openDialog));
    bindToComponent(imageSurface, null, rThread closeStream);
  }
  
  visual
    centerAndSouthWithMargin(
      jscroll_center_borderless(imageSurface),
      buttons
    );
    
  void openDialog swing {
    new JFileChooser fc;
    fc.setDialogTitle("Open video");
    play(execFileChooser(fc));
  }
  
  void play(File videoFile) {
    if (videoFile == null) ret;
    pcall-infobox {
      closeStream();
      stream = new ImageStreamFromVideoFile;
      stream.open(videoFile);
      stream.onHaveImage((image, pos) -> {
        // TODO: sleep
        if (playStartTime == 0)
          playStartTime = sysNow()-pos.toMillis();
        else
          sleepUntil(playStartTime+pos.toMillis());
        imageSurface.setImage(image);
      });
      stream.startDecodeThread();
    }
  }
  
  void closeStream {
    imageSurface.noImage();
    dispose stream;
    playStartTime = 0;
  }
}