code: func (l *ListBox) PartialFindItem(text string, caseSensitive bool) int {
  	if !caseSensitive {
  		text = strings.ToLower(text)
  	}
  
  	for idx, itm := range l.items {
  		if caseSensitive {
  			if strings.HasPrefix(itm, text) {
  				return idx
  			}
  		} else {
  			low := strings.ToLower(itm)
  			if strings.HasPrefix(low, text) {
  				return idx
  			}
  		}
  	}
  
  	return -1
  }
docs: // PartialFindItem looks for an item in list which text starts from
  // the given substring, by default the search is casesensitive.
  // Returns item number in item list or -1 if nothing is found.