sclass JGallery_v2 {
  JPanel panel = jpanel(new VScrollingWrapLayout);
  
  settable new ThumbnailCache thumbnailCache;
  
  event adaptingButton(JThumbnailButton btn);
  event fileClicked(File imageFile);
  
  void add(File imageFile) {
    if (imageFile == null) ret;
    addComponent(panel, makeButton(imageFile));
  }
  
  JThumbnailButton makeButton(File imageFile) {
    var btn = new JThumbnailButton(thumbnailCache, imageFile);
    onClick(btn, rThread { fileClicked(btn.imageFile()) });
    adaptingButton(btn);
    ret btn;
  }
  
  void setImageFiles(Cl<File> imageFiles) {
    removeAllButtons();
    addAll(imageFiles);
  }
  
  void addAll(Iterable<File> imageFiles) {
    fOr (f : imageFiles) add(f);
  }
  
  L<JThumbnailButton> buttons() {
    ret childrenOfType(panel, JThumbnailButton);
  }
  
  void removeAllButtons {
    removeAllComponents(panel);
  }
  
  JThumbnailButton findButton(File imageFile) {
    if (imageFile == null) null;
    ret first(buttons(), btn -> eq(btn.imageFile, imageFile));
  }
  
  cachedVisual
    jscroll_vertical(panel);
    
  void unselectAll() swing {
    for (btn : buttons())
      btn.setSelected(false);
  }
    
  JThumbnailButton selectFile(File imageFile) swing {
    unselectAll();
    var btn = findButton(imageFile);
    if (btn != null) {
      btn.setSelected(true);
      scrollIntoView(btn);
    }
    ret btn;
  }
}