!7

cmodule BigInputWithSections {
  S text;
  switchable int fontSize = 20;
  
  transient JPanel stack;
  transient StackLayouter layouter;
  transient new AtomicLong changeCount;
  transient long renderedChangeCount;
  
  void triggerMakeSections {
    incAtomicLong(changeCount); makeSections();
  }
  
  start {
    onChange(r triggerMakeSections);
  }

  visual
    withComputing(r triggerMakeSections, jvsplit(setFontSize(fontSize, dm_textArea('text)),
      jscroll_trackWidth(stack = customLayoutPanel(layouter = new StackLayouter))));
      
  void makeSections() q {
    if (stack == null) ret;
    long c = changeCount!;
    if (renderedChangeCount >= c) ret;
    renderedChangeCount = c;
    
    removeAllComponents(stack);
    addAndValidate(stack, jSection("Character count", jlabel(l_str(text))));
  }
}