def checkout_button(button_opts = {})
      @xml or to_xml
      burl = button_url(button_opts)
      html = Builder::XmlMarkup.new(:indent => 2)
      html.form({
                  :action => submit_url,
                  :style => 'border: 0;',
                  :id => 'BB_BuyButtonForm',
                  :method => 'post',
                  :name => 'BB_BuyButtonForm'
                }) do
        html.input({
                     :name => 'cart',
                     :type => 'hidden',
                     :value => Base64.encode64(@xml).gsub("\n", '')
                   })
        html.input({
                     :name => 'signature',
                     :type => 'hidden',
                     :value => Base64.encode64(signature).gsub("\n", '')
                   })
        html.input({
                     :alt => 'Google Checkout',
                     :style => "width: auto;",
                     :src => button_url(button_opts),
                     :type => 'image'
                   })
      end
    end
def checkout_button(button_opts = {})
      @xml or to_xml
      burl = button_url(button_opts)
      html = Builder::XmlMarkup.new(:indent => 2)
      html.form({
                  :action => submit_url,
                  :style => 'border: 0;',
                  :id => 'BB_BuyButtonForm',
                  :method => 'post',
                  :name => 'BB_BuyButtonForm'
                }) do
        html.input({
                     :name => 'cart',
                     :type => 'hidden',
                     :value => Base64.encode64(@xml).gsub("\n", '')
                   })
        html.input({
                     :name => 'signature',
                     :type => 'hidden',
                     :value => Base64.encode64(signature).gsub("\n", '')
                   })
        html.input({
                     :alt => 'Google Checkout',
                     :style => "width: auto;",
                     :src => button_url(button_opts),
                     :type => 'image'
                   })
      end
    end
Returns HTML for a checkout form for buying all the items in the
 cart.