Symfony 1.4 FormFilter: how to add "is not empty" checkbox?

I use a FormFilter on a class of my model, and it's very useful to me. But I need a feature that does not seem to exist.

I already use the "with_empty" option to add an "is empty" checkbox next to a field. It filters the objects to display only the ones that have a NULL value in this field. But I need to do the opposite. I want to add an "is not empty" checkbox to display the objects that have a NOT NULL value in this field.

So I've created this widget class to display the additional checkbox:

<?php
/**
 * sfWidgetFormFilterInputExtended represents an HTML input tag used for filtering text.
 * It adds the possibility to insert a "is not empty" checkbox that does the opposite
 * of "is empty" checkbox
 */
class sfWidgetFormFilterInputExtended extends sfWidgetFormFilterInput
{
  protected function configure($options = array(), $attributes = array())
  {
    parent::configure($options, $attributes);
    $this->addOption('with_not_empty', true);
    $this->addOption('not_empty_label', 'is not empty');
    $this->addOption('template', '%input%<br />%empty_checkbox% %empty_label%<br />%not_empty_checkbox% %not_empty_label%');
  }

  /**
   * @param  string $name        The element name
   * @param  string $value       The value displayed in this widget
   * @param  array  $attributes  An array of HTML attributes to be merged with the default HTML attributes
   * @param  array  $errors      An array of errors for the field
   *
   * @return string An HTML tag string
   *
   * @see sfWidgetForm
   */
  public function render($name, $value = null, $attributes = array(), $errors = array())
  {
    $values = array_merge(
      array(
        'text' => '',
        'is_empty' => false,
        'is_not_empty' => false,
      ),
      is_array($value) ? $value : array()
    );

    return strtr($this->getOption('template'), array(
      '%input%'              => $this->renderTag('input', array_merge(array('type' => 'text', 'id' => $this->generateId($name), 'name' => $name.'[text]', 'value' => $values['text']), $attributes)),
      '%empty_checkbox%'     => $this->getOption('with_empty') ? $this->renderTag('input', array('type' => 'checkbox', 'name' => $name.'[is_empty]', 'checked' => $values['is_empty'] ? 'checked' : '')) : '',
      '%empty_label%'        => $this->getOption('with_empty') ? $this->renderContentTag('label', $this->translate($this->getOption('empty_label')), array('for' => $this->generateId($name.'[is_empty]'))) : '',
      '%not_empty_checkbox%' => $this->getOption('with_not_empty') ? $this->renderTag('input', array('type' => 'checkbox', 'name' => $name.'[is_not_empty]', 'checked' => $values['is_not_empty'] ? 'checked' : '')) : '',
      '%not_empty_label%'    => $this->getOption('with_not_empty') ? $this->renderContentTag('label', $this->translate($this->getOption('not_empty_label')), array('for' => $this->generateId($name.'[is_not_empty]'))) : '',
    ));
  }
}

But now, my problem is that I have to handle the "is_not_empty" value in my forms manually...

How would you implement that in a better way?

Thanks!

PS: I use Doctrine

Please see sfFormFilterDoctrine::doBuildQuery method.

In brief you need to implement add%sColumnQuery.