Apache Solr Panels Integration

First, please see Better Integration with Apache Solr Autocomplete.

As summarized in that issue, I would like to control what fields are queried via the Solr QF parameter in the Solr Panels pane settings form.

If interested in the following approach, I would be happy to submit a patch.

The basic idea of my approach was to utilize the unused jquey-autocomplete configuration point 'extraParams'. And so that this wasn't just limited to Apache Solr Panels, I was thinking something like this:

Drupal.behaviors.apachesolr_autocomplete = function(context) {
  $(".apachesolr-autocomplete.unprocessed", context).autocomplete(Drupal.settings.apachesolr_autocomplete.path,
  {
    // Classnames for the widget.
    inputClass: "",
   
  ......

    extraParams: {
       apachesolr_autocomplete_overrides: function() { return $("#apachesolr-autocomplete-overrides").val(); },
    },

And, the value of #apachesolr-autocomplete-overrides would be a json-encoded PHP object/array of values that would could be documented and used by any module and added as part of a hook_form_alter(), like so:

/**
 * Implementation of hook_form_FORM_ID_alter().
 */
function apachesolr_panels_form_apachesolr_panels_search_form_alter(&$form, &$form_state) {

  ...

    $apachesolr_autocomplete_overrides_value = array();
    $apachesolr_autocomplete_overrides_value['fq'] = explode(' ', $form_state['apachesolr_autocomplete_fq']);
    $apachesolr_autocomplete_overrides_value['facet_field'] = explode(' ', $form_state['apachesolr_autocomplete_facet_field']);
    $apachesolr_autocomplete_overrides_value['qf'] = explode(' ', $form_state['apachesolr_autocomplete_qf']);
    $form['basic']['apachesolr_panels_search']['apachesolr_autocomplete_overrides'] = array(
      '#type' => 'hidden',
      '#id' => 'apachesolr-autocomplete-overrides',
      // We use JSON encoding instead of PHP serialize, since otherwise we be
      // at risk of user input being injected into the hidden string and
      // unserialized.
      '#default_value' => json_encode($apachesolr_autocomplete_overrides_value),
    );
  }
}

Then, apachesolr_autocomplete.module would be modified to utilize those additional Solr overrides. Another example:

function apachesolr_autocomplete_suggest_word_completion($keys, $suggestions_to_return = 5) {
  $apachesolr_autocomplete_overrides = json_decode($_GET['apachesolr_autocomplete_overrides']);

  ...

  // Ask Solr to return facets that begin with $last_part; these will be the suggestions.
  $facet_field = array('spell');
  if (!empty($apachesolr_autocomplete_overrides->facet_field)) {
    $facet_field = $apachesolr_autocomplete_overrides->facet_field;
  }
  $params = array(
    'facet' => 'true',
    'facet.field' => $facet_field,
    'facet.prefix' => $last_part,
    'facet.limit' => $suggestions_to_return * 5,
    'facet.mincount' => 1,
    'start' => 0,
    'rows' => 0,
  );
  if (!empty($apachesolr_autocomplete_overrides->fq)) {
    $add_filters_array = $apachesolr_autocomplete_overrides->fq;
  }
  if (!empty($apachesolr_autocomplete_overrides->qf)) {
    $params['qf'] = $apachesolr_autocomplete_overrides->qf;
  }

  ...

}

Finally:

function apachesolr_autocomplete_suggest($keys, $params, $theme_callback, $orig_keys, $suggestions_to_return = 5, $add_filters_array = NULL) {
  
  ...

  // Query Solr for $keys so that suggestions will always return results.
  $query = apachesolr_drupal_query($keys);
  //add additional filters if any and have both key and value
  if ($add_filters_array) {
    foreach ($add_filters_array as $add_filter) {
      $filter_array = explode(':', $add_filter);
      if (!empty($filter_array[0]) && !empty($filter_array[1])) {
        $query->add_filter($filter_array[0], $filter_array[1]);
      }
    }
  }

  ...

}

And this give you the basic idea.