code: private void updateContext(Container c ,int maxCtx, int ctxSteps, boolean keepCustomValues)
    {
  
      if(!keepCustomValues)
      {
        c.removeAllItems();
      }
      
      for (Integer i : PREDEFINED_CONTEXTS)
      {
        if (i < maxCtx)
        {
          c.addItem(i);
        }
      }
  
      for (int step = ctxSteps; step < maxCtx; step += ctxSteps)
      {
        c.addItem(step);
      }
  
      c.addItem(maxCtx);
  
    }
docs: Updates context combo boxes.
  
  @param c the container, which is updated.
  @param maxCtx the larges context values until context steps are calculated.
  @param ctxSteps the step range.
  @param keepCustomValues If this is true all custom values are kept.