How to embed mercury in new action without losing ability to use select fields or any other form fields. This form is the part of a gem 'HowTo', so edit this page as per your requirements

gistfile1.txt

<!-- This section is important as it redirect to editor mode and handle form submition-->
<script type="text/javascript">
    <% if rich_text_enabled && params[:rich_text_enabled].nil? %>
    location.href = "<%= "/editor" + request.path + "?rich_text_enabled=1"%>"
    <% end %>

    jQuery(window).on('mercury:ready', function () {

        $('#how_to_content_submit').on('click', function () {
            $.each($('[contenteditable=true]'), function () {
                if ($(this).attr('target_id')) {
                    $('#' + $(this).attr('target_id')).val($(this).html())
                }
            });
            Mercury.changes = false;
        });

        Mercury.PageEditor.prototype.save = function () {
            Mercury.changes = false;
            $('#how_to_content_submit').trigger('click');
        }

    });

</script>

<%= form_for @content, :html => {:class => 'form-horizontal'} do |f| %>
    <fieldset>
      <legend><%= controller.action_name.capitalize %> Content</legend>

      <div class="control-group">
        <%= f.label :section, :class => 'control-label' %>
        <div class="controls">
          <%= f.select :section_id, OPTIONS, {:prompt => 'select'}, :'chosen-enabled' => true %>
        </div>
      </div>

          <div class="control-group">
            <%= f.label :title, "Title for #{locale}", :class => 'control-label' %>
            <div class="controls">
                  <div target_id="<%= "MERCURY_ENABLED_FIELD_ID" %>" contenteditable="true" data-mercury="full">
                    <%= raw f.object.send("i18n_#{locale.to_s}_title".to_sym) %>
                  </div>
                  <%= f.hidden_field "MERCURY_ENABLED_FIELD", :class => 'text_field' %>
             
            </div>
          </div>
    
        <div class="control-group">
            <%= f.label :title, "Title for #{locale}", :class => 'control-label' %>
            <div class="controls">
<!-- relace the form field with these following 4 lines to enable mercury-->
                  <div target_id="<%= "MERCURY_ENABLED_FIELD_ID" %>" contenteditable="true" data-mercury="full">
                    <%= raw f.object.send(MERCURY_ENABLED_FIELD.to_sym) %>
                  </div>
                  <%= f.hidden_field "MERCURY_ENABLED_FIELD", :class => 'text_area' %>
             
            </div>
          </div>
    
            
      

      <div class="control-group">
        <%= f.label :order, :class => 'control-label' %>
        <div class="controls">
          <%= f.text_field :order, :class => 'text_field' %>
        </div>
      </div>
      <div class="form-actions">
        <%= f.submit nil, :class => 'btn btn-primary', id: 'how_to_content_submit' %>
        <%= link_to 'Cancel', contents_path, :class => 'btn' %>
      </div>
    </fieldset>
<% end %>