## Goal [plaintext]
  <option>Root category</option>
  <option>  Sub category 1</option>
  <option>  Sub category 2</option>
  <option>    Sub-sub category</option>
  <option selected="selected">    Selected category</option

## Current code (ugly) [ruby]
<%

def render_category(category)
  code = ""

  category.categories.each do |c|
    code += render_category c
  end

  code += "<option"

  if category.id == @chart.category_id
    code += " selected=\"selected\""
  end

  code += ">"
  code += h(category.title)
  code += "</option>"
end

Category.find(:all, :conditions => ["category_id IS NULL"]).each do |c|
%>
  <%= render_category c %>
<% end %>