EDIT

// see also https://github.com/geetarista/jquery-plugin-template/blob/master/jquery.plugin-template.js

/**

 * Expected DOM structure:

 *

 * <div id="cdm_taxontree_parent">

 *      <div class="cdm_taxontree_scroller_xy">

 *              <ul class="cdm_taxontree">

 *                  <li class="leaf filter_included">

 *                      <a href="/d7/test/cdm_dataportal/taxon/996dc2b4-e73d-4d40-99f9-fac18b503d1c"></a>

 *                  </li>

 *                  ...

 *              </ul>

 *      </div>

 * </div>

 */

;(function($, document, window, undefined) {

    $.fn.cdm_taxontree = function(options) {

    var opts = $.extend({}, $.fn.cdm_taxontree.defaults, options);

    var vertical_scroller_selector = 'cdm_taxontree_scroller_xy';

    var cdm_taxontree_parent = $(this);

    var cdm_taxontree_list = cdm_taxontree_parent.find('ul.cdm_taxontree');

      /* ----------- magicbox ---------- */

      if (opts.magicbox) {

        cdm_taxontree_parent.cdm_taxontree_magicbox();

        vertical_sroller_selector =  'cdm_taxontree_scroller_x';

      }

      /* ----------- tree browser ---------- */

      cdm_taxontree_list.delegate("li:not(.invisible)", "click", function(event) {

              handle_taxon_node_click(event);

          }

      );

      // Stop event propagation for links (unclear why this is nessecary,

      // was this needed for the filter buttons?)

      cdm_taxontree_list.delegate("li a", "click", function(event) {

              event.stopPropagation();

          }

      );

      /* ----------- widget ------------------- */

      if (opts.widget) {

        var widget = cdm_taxontree_parent.find('.cdm_taxontree_widget');

        var optionList = widget.find('select');

        // Keep all options unselected.

        optionList.change(function() {

            cdm_taxontree_list.children("[@selected]").remove();

            cdm_taxontree_list.children().removeAttr('selected');

        });

        optionList.children("[@selected]").click(function() {

            cdm_taxontree_list.remove();

        });

        // Select all options onsubmit.

        optionList.parents('form').submit(function() {

          optionList.children().attr('selected', 'selected');

        });

        bind_select_click(optionList, cdm_taxontree_list, opts.multiselect);

      };

      // finally scroll to the focused element

      scrollToFocused();

    /**

     * handler function for clicks on the li elelements which

     * represent CDM TaxonNodes. The click will load the

     * nodes children via an AHAH call to the CdmdataPortal

     * and expands the clicked node.

     *

     * @param event

     *   The javascript event object of the click event

     */

    function handle_taxon_node_click(event){

        event.stopPropagation();

        var li = $(event.target);

        if (li.hasClass('collapsed')) {

          var bindChildren = (li.find('ul').length == 0);

          if (bindChildren) {

            var url = li.attr('data-cdm-ahah-url');

            if (url != undefined) {

              li.removeAttr('data-cdm-ahah-url');

              var parent_li = li;

              li.set_background_image('loading_subtree.gif');

              // Load DOM subtree via AHAH and append it.

              $.get(url, function(html) {

                parent_li.set_background_image('minus.png');

                if (opts.magicbox) {

                  // Preserve scroll positions.

                  var tmp_scroller_y_left = parent_li.parents('div.cdm_taxontree_container').children().scrollTop();

                  parent_li.append(html);

                  // Resize parent container.

                  cdm_taxontree_container_resize(tree_container);

                  // Restore scroll positions.

                  tree_container.children().scrollTop(tmp_scroller_y_left);

                } else {

                  parent_li.append(html);

                }

              });

            }

          } else {

            li.set_background_image('minus.png');

          }

          li.removeClass('collapsed').addClass('expanded').children(

              'ul').css('display', 'block');

        } else if (li.hasClass('expanded')) {

          li.removeClass('expanded').addClass('collapsed').children(

              'ul').css('display', 'none');

          li.set_background_image('plus.png');

        }

    };

    /**

     *

     */

    function bind_select_click(optionList, treelist, isMultiselect) {

      treelist.find('li .widget_select').click(

          function(event) {

            event.stopPropagation();

            var li_widget_select = $(event.target);

            var value = li_widget_select.attr('alt');

            if (optionList.children('[value=' + value + ']').length > 0) {

              // Remove from select.

              optionList.children('[value=' + value + ']').remove();

            } else {

              // Add to select.

              if (!isMultiselect) {

                // Remove all from select

                optionList.children().remove();

              }

              optionList.append('<option value="' + value + '">'

                  + li_widget_select.attr('title') + '</option>');

              // Fix bug in IE.

              if (jQuery.browser['msie']) {

                if (jQuery.browser['version'].charAt(0) <= '6') {

                  return;

                }

              }

              // optionList.children().removeAttr('selected'); // Yields a bug

              // in IE6, @see

              // http://gimp4you.eu.org/sandbox/js/test/removeAttr.html

              optionList.children("[@selected]").attr('selected', '');

            }

          });

    } // END bind_select_click()

    /**

     *

     */

    function scrollToFocused() {

        var focusedElement = cdm_taxontree_parent.find('.focused');

        if(focusedElement.length > 0){

            var lineHeight = focusedElement.css('line-height');

            lineHeight = lineHeight.replace('px', '');

            lineHeight = lineHeight.length == 0 ? 18 : lineHeight;

            cdm_taxontree_parent.find('div.' + vertical_scroller_selector).scrollTo(focusedElement, {duration: 400, axis:'y', offset:-2 * lineHeight});

        }

    }

  }; // END cdm_taxontree()

})(jQuery, document, window);

/**

 * helper function to set the background image as jQuery extension

 */

jQuery.fn.set_background_image = function(imageFile) {

  var bg_image_tmp = jQuery(this).css('background-image');

  var bg_image_new = bg_image_tmp.replace(/^(.*)(\/.*)(\))$/, '$1/' + imageFile + '$3');

  if (jQuery.browser.mozilla) {

    // Special bug handling for mozilla: strip of last closing bracket.

    bg_image_new = bg_image_new.substr(0, bg_image_new.length - 1);

  }

  jQuery(this).css('background-image', bg_image_new);

};

jQuery.fn.cdm_taxontree.defaults = { // Set up default options.

        widget : false, // True = enable widget mode.

        magicbox : false, // True = enable quirky magicbox.

        element_name : 'widgetval',

        multiselect : false // True = enable selection of multiple.

};

// ====================================================================================== //

/**

 * jQuery function which implements the Magicbox behavior for the taxontree.

 * A Magicbox the container of the taxon tree will extend on mouse over

 * events in order to show the entrys without truncation through cropping.

 */

jQuery.fn.cdm_taxontree_magicbox = function() {

  // Exclude IE6 and lower versions.

  if (!(jQuery.browser['msie'] && jQuery.browser['version'].charAt(0) < '7')) {

    var container = $(this).parent().parent('div.cdm_taxontree_container');

    if (container[0] != undefined) {

        container.hover(

            function(event) {

                handle_mouseOver(event);

            },

            function(event) {

                handle_mouseOut(event);

            }

        );

    }

  } // END exclude IE6

  /**

   * expands the box on mouse over events the

   */

  function handle_mouseOver(event){

      var taxontree_container = $(event.target);

      var scroller_x = taxontree_container.parent();

      var scroller_y = taxontree_container.children('.cdm_taxontree_scroller_y');

      var container = scroller_x.parent();

      var h = parseFloat(scroller_x.height());

      var scroll_top = scroller_x.scrollTop();

      var border_color = scroller_x.css('border-top-color');

      // Store scroll_left of scroller_x so that it can be restored on mouseOut.

      scroller_x.append('<div class="_scrollLeft" style="display: none;" title="'

              + scroller_x.scrollLeft() + '"></div>');

      var newWidth = cdm_taxontree_container_resize(taxontree_container);

      var shift_left = '0';

      if (scroller_x.hasClass('expand-left')) {

        shift_left = container.outerWidth({margin : true}) - newWidth;

      }

      scroller_y.css('overflow-y', 'auto')

          .css('border-color', border_color)

          .scrollTop(scroll_top);

      scroller_x.css('overflow-y', 'visible')

          .css('overflow-x', 'visible')

          .css('margin-left', shift_left)

          .css('border-color', 'transparent')

          .height(h);

  };

  /**

   * Restores the original appearance on mouse out events

   */

  function handle_mouseOut(event){

      var taxontree_container = $(event.target);

      var scroller_x = taxontree_container.parent('.cdm_taxontree_scroller_x');

      var scroller_y = taxontree_container.children('.cdm_taxontree_scroller_y');

      var border_color = scroller_y.css('border-top-color');

      var scroll_top = scroller_y.scrollTop();

      scroller_y.css('overflow-y', 'visible')

          .css('border-color', 'transparent');

      scroller_x.css('overflow-y', 'auto').css('margin-left', '0').css(

          'border-color', border_color).width('auto').scrollTop(scroll_top);

      // Restore scroll_left of scroller_x.

      var scrollLeft = scroller_x.children('._scrollLeft').attr('title');

      scroller_x.scrollLeft(scrollLeft);

      scroller_x.children('._scrollLeft').remove();

  };

  /**

   * Resizes the taxontree_container and returns the new outerWidth

   */

  function taxontree_container_resize(taxontree_container) {

    var current_w = taxontree_container.parent().width();

    // Determine max horizontal extent of any children.

    var tree_list = taxontree_container.find('.cdm_taxontree_scroller_y > ul');

    var w = tree_list.css('position', 'absolute').outerWidth({

      margin : true

    });

    tree_list.css('position', 'static');

    // Other Browsers than Firefox.

    if (jQuery.browser['msie']) {

      if (jQuery.browser['version'].charAt(0) == '7') {

        w = w + 17;

      }

      if (jQuery.browser['version'].charAt(0) <= '6') {

        return;

      }

    }

    if (current_w < w) {

        taxontree_container.parent().width(w);

        taxontree_container.children().width(w);

    }

    return taxontree_container.children().outerWidth();

  };

  /**

   * Debug function, currently unused

   */

  function cdm_taxontree_container_debug_size(taxontree_container, msg) {

      var out = msg + '<br />    scoll_x: ' + taxontree_container.parent().width()

          + '<br />    container: ' + taxontree_container.width() + '<br />    scoll_y: '

          + taxontree_container.children().width() + '<br />    ul: '

          + taxontree_container.find('.cdm_taxontree_scroller_y > ul').width() + '<br />';

      jQuery('#DEBUG_JS').append(out);

  };

};

//====================================================================================== //