--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/program/js/treelist.js	Thu Jan 04 15:52:31 2018 -0500
@@ -0,0 +1,1205 @@
+/**
+ * Roundcube Treelist Widget
+ *
+ * This file is part of the Roundcube Webmail client
+ *
+ * @licstart  The following is the entire license notice for the
+ * JavaScript code in this file.
+ *
+ * Copyright (c) 2013-2014, The Roundcube Dev Team
+ *
+ * The JavaScript code in this page is free software: you can
+ * redistribute it and/or modify it under the terms of the GNU
+ * General Public License (GNU GPL) as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option)
+ * any later version.  The code is distributed WITHOUT ANY WARRANTY;
+ * without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU GPL for more details.
+ *
+ * As additional permission under GNU GPL version 3 section 7, you
+ * may distribute non-source (e.g., minimized or compacted) forms of
+ * that code without the copy of the GNU GPL normally required by
+ * section 4, provided you include this license notice and a URL
+ * through which recipients can access the Corresponding Source.
+ *
+ * @licend  The above is the entire license notice
+ * for the JavaScript code in this file.
+ *
+ * @author Thomas Bruederli <roundcube@gmail.com>
+ * @requires jquery.js, common.js
+ */
+
+
+/**
+ * Roundcube Treelist widget class
+ * @constructor
+ */
+function rcube_treelist_widget(node, p)
+{
+  // apply some defaults to p
+  p = $.extend({
+    id_prefix: '',
+    autoexpand: 1000,
+    selectable: false,
+    scroll_delay: 500,
+    scroll_step: 5,
+    scroll_speed: 20,
+    save_state: false,
+    keyboard: true,
+    tabexit: true,
+    parent_focus: false,
+    check_droptarget: function(node) { return !node.virtual; }
+  }, p || {});
+
+  var container = $(node),
+    data = p.data || [],
+    indexbyid = {},
+    selection = null,
+    drag_active = false,
+    search_active = false,
+    last_search = '',
+    has_focus = false,
+    box_coords = {},
+    item_coords = [],
+    autoexpand_timer,
+    autoexpand_item,
+    body_scroll_top = 0,
+    list_scroll_top = 0,
+    scroll_timer,
+    searchfield,
+    tree_state,
+    ui_droppable,
+    ui_draggable,
+    draggable_opts,
+    droppable_opts,
+    list_id = (container.attr('id') || p.id_prefix || '0'),
+    me = this;
+
+
+  /////// export public members and methods
+
+  this.container = container;
+  this.expand = expand;
+  this.collapse = collapse;
+  this.select = select;
+  this.render = render;
+  this.reset = reset;
+  this.drag_start = drag_start;
+  this.drag_end = drag_end;
+  this.intersects = intersects;
+  this.droppable = droppable;
+  this.draggable = draggable;
+  this.update = update_node;
+  this.insert = insert;
+  this.remove = remove;
+  this.get_item = get_item;
+  this.get_node = get_node;
+  this.get_selection = get_selection;
+  this.is_search = is_search;
+  this.reset_search = reset_search;
+
+  /////// startup code (constructor)
+
+  // abort if node not found
+  if (!container.length)
+    return;
+
+  if (p.data)
+    index_data({ children:data });
+  // load data from DOM
+  else
+    update_data();
+
+  // scroll to the selected item
+  if (selection) {
+    scroll_to_node(id2dom(selection, true));
+  }
+
+  container.attr('role', 'tree')
+    .on('focusin', function(e) {
+      // TODO: only accept focus on virtual nodes from keyboard events
+      has_focus = true;
+    })
+    .on('focusout', function(e) {
+      has_focus = false;
+    })
+    // register click handlers on list
+    .on('click', 'div.treetoggle', function(e) {
+      toggle(dom2id($(this).parent()));
+      e.stopPropagation();
+    })
+    .on('click', 'li', function(e) {
+      // do not select record on checkbox/input click
+      if ($(e.target).is('input'))
+        return true;
+
+      var node = p.selectable ? indexbyid[dom2id($(this))] : null;
+      if (node && !node.virtual) {
+        select(node.id);
+        e.stopPropagation();
+      }
+    })
+    // mute clicks on virtual folder links (they need tabindex="0" in order to be selectable by keyboard)
+    .on('mousedown', 'a', function(e) {
+      var link = $(e.target), node = indexbyid[dom2id(link.closest('li'))];
+      if (node && node.virtual && !link.attr('href')) {
+        e.preventDefault();
+        e.stopPropagation();
+        return false;
+      }
+    });
+
+  // activate search function
+  if (p.searchbox) {
+    searchfield = $(p.searchbox).off('keyup.treelist').on('keyup.treelist', function(e) {
+      var key = rcube_event.get_keycode(e),
+        mod = rcube_event.get_modifier(e);
+
+      switch (key) {
+        case 9:   // tab
+          break;
+
+        case 13:  // enter
+          search(this.value, true);
+          return rcube_event.cancel(e);
+
+        case 27:  // escape
+          reset_search();
+          break;
+
+        case 38:  // arrow up
+        case 37:  // left
+        case 39:  // right
+        case 40:  // arrow down
+          return;  // ignore arrow keys
+
+        default:
+          search(this.value, false);
+          break;
+      }
+    }).attr('autocomplete', 'off');
+
+    // find the reset button for this search field
+    searchfield.parent().find('a.reset').off('click.treelist').on('click.treelist', function(e) {
+      reset_search();
+      return false;
+    })
+  }
+
+  $(document.body).on('keydown', keypress);
+
+  // catch focus when clicking the list container area
+  if (p.parent_focus) {
+    container.parent(':not(body)').click(function(e) {
+      // click on a checkbox does not catch the focus
+      if ($(e.target).is('input'))
+        return true;
+
+      if (!has_focus && selection) {
+        $(get_item(selection)).find(':focusable').first().focus();
+      }
+      else if (!has_focus) {
+        container.children('li:has(:focusable)').first().find(':focusable').first().focus();
+      }
+    });
+  }
+
+  /////// private methods
+
+  /**
+   * Collaps a the node with the given ID
+   */
+  function collapse(id, recursive, set)
+  {
+    var node;
+
+    if (node = indexbyid[id]) {
+      node.collapsed = typeof set == 'undefined' || set;
+      update_dom(node);
+
+      if (recursive && node.children) {
+        for (var i=0; i < node.children.length; i++) {
+          collapse(node.children[i].id, recursive, set);
+        }
+      }
+
+      me.triggerEvent(node.collapsed ? 'collapse' : 'expand', node);
+      save_state(id, node.collapsed);
+    }
+  }
+
+  /**
+   * Expand a the node with the given ID
+   */
+  function expand(id, recursive)
+  {
+    collapse(id, recursive, false);
+  }
+
+  /**
+   * Toggle collapsed state of a list node
+   */
+  function toggle(id, recursive)
+  {
+    var node;
+    if (node = indexbyid[id]) {
+      collapse(id, recursive, !node.collapsed);
+    }
+  }
+
+  /**
+   * Select a tree node by it's ID
+   */
+  function select(id)
+  {
+    // allow subscribes to prevent selection change
+    if (me.triggerEvent('beforeselect', indexbyid[id]) === false) {
+      return;
+    }
+
+    if (selection) {
+      id2dom(selection, true).removeClass('selected').removeAttr('aria-selected');
+      if (search_active)
+          id2dom(selection).removeClass('selected').removeAttr('aria-selected');
+      selection = null;
+    }
+
+    if (!id)
+      return;
+
+    var li = id2dom(id, true);
+    if (li.length) {
+      li.addClass('selected').attr('aria-selected', 'true');
+      selection = id;
+      // TODO: expand all parent nodes if collapsed
+
+      if (search_active)
+        id2dom(id).addClass('selected').attr('aria-selected', 'true');
+
+      scroll_to_node(li);
+    }
+
+    me.triggerEvent('select', indexbyid[id]);
+  }
+
+  /**
+   * Getter for the currently selected node ID
+   */
+  function get_selection()
+  {
+    return selection;
+  }
+
+  /**
+   * Return the DOM element of the list item with the given ID
+   */
+  function get_node(id)
+  {
+    return indexbyid[id];
+  }
+
+  /**
+   * Return the DOM element of the list item with the given ID
+   */
+  function get_item(id, real)
+  {
+    return id2dom(id, real).get(0);
+  }
+
+  /**
+   * Insert the given node
+   */
+  function insert(node, parent_id, sort)
+  {
+    var li, parent_li,
+      parent_node = parent_id ? indexbyid[parent_id] : null
+      search_ = search_active;
+
+    // ignore, already exists
+    if (indexbyid[node.id]) {
+      return;
+    }
+
+    // apply saved state
+    state = get_state(node.id, node.collapsed);
+    if (state !== undefined) {
+      node.collapsed = state;
+    }
+
+    // insert as child of an existing node
+    if (parent_node) {
+      node.level = parent_node.level + 1;
+      if (!parent_node.children)
+        parent_node.children = [];
+
+      search_active = false;
+      parent_node.children.push(node);
+      parent_li = id2dom(parent_id);
+
+      // re-render the entire subtree
+      if (parent_node.children.length == 1) {
+        render_node(parent_node, null, parent_li);
+        li = id2dom(node.id);
+      }
+      else {
+        // append new node to parent's child list
+        li = render_node(node, parent_li.children('ul').first());
+      }
+
+      // list is in search mode
+      if (search_) {
+        search_active = search_;
+
+        // add clone to current search results (top level)
+        if (!li.is(':visible')) {
+          $('<li>')
+            .attr('id', li.attr('id') + '--xsR')
+            .attr('class', li.attr('class'))
+            .addClass('searchresult__')
+            .append(li.children().first().clone(true, true))
+            .appendTo(container);
+        }
+      }
+    }
+    // insert at top level
+    else {
+      node.level = 0;
+      data.push(node);
+      li = render_node(node, container);
+    }
+
+    indexbyid[node.id] = node;
+
+    // set new reference to node.html after insert
+    // will otherwise vanish in Firefox 3.6
+    if (typeof node.html == 'object') {
+        indexbyid[node.id].html = id2dom(node.id, true).children();
+    }
+
+    if (sort) {
+      resort_node(li, typeof sort == 'string' ? '[class~="' + sort + '"]' : '');
+    }
+  }
+
+  /**
+   * Update properties of an existing node
+   */
+  function update_node(id, updates, sort)
+  {
+    var li, parent_ul, parent_node, old_parent,
+      node = indexbyid[id];
+
+    if (node) {
+      li = id2dom(id);
+      parent_ul = li.parent();
+
+      if (updates.id || updates.html || updates.children || updates.classes || updates.parent) {
+        if (updates.parent && (parent_node = indexbyid[updates.parent])) {
+          // remove reference from old parent's child list
+          if (parent_ul.closest('li').length && (old_parent = indexbyid[dom2id(parent_ul.closest('li'))])) {
+            old_parent.children = $.grep(old_parent.children, function(elem, i){ return elem.id != node.id; });
+          }
+
+          // append to new parent node
+          parent_ul = id2dom(updates.parent).children('ul').first();
+          if (!parent_node.children)
+            parent_node.children = [];
+          parent_node.children.push(node);
+        }
+        else if (updates.parent !== undefined) {
+          parent_ul = container;
+        }
+
+        $.extend(node, updates);
+        li = render_node(node, parent_ul, li);
+      }
+
+      if (node.id != id) {
+        delete indexbyid[id];
+        indexbyid[node.id] = node;
+      }
+
+      if (sort) {
+        resort_node(li, typeof sort == 'string' ? '[class~="' + sort + '"]' : '');
+      }
+    }
+  }
+
+  /**
+   * Helper method to sort the list of the given item
+   */
+  function resort_node(li, filter)
+  {
+    var first, sibling,
+      myid = li.get(0).id,
+      sortname = li.children().first().text().toUpperCase();
+
+    li.parent().children('li' + filter).each(function(i, elem) {
+      if (i == 0)
+        first = elem;
+      if (elem.id == myid) {
+        // skip
+      }
+      else if (elem.id != myid && sortname >= $(elem).children().first().text().toUpperCase()) {
+        sibling = elem;
+      }
+      else {
+        return false;
+      }
+    });
+
+    if (sibling) {
+      li.insertAfter(sibling);
+    }
+    else if (first && first.id != myid) {
+      li.insertBefore(first);
+    }
+
+    // reload data from dom
+    update_data();
+  }
+
+  /**
+   * Remove the item with the given ID
+   */
+  function remove(id)
+  {
+    var node, li, parent;
+
+    if (node = indexbyid[id]) {
+      li = id2dom(id, true);
+      parent = li.parent();
+      li.remove();
+
+      node.deleted = true;
+      delete indexbyid[id];
+
+      if (search_active) {
+        id2dom(id, false).remove();
+      }
+
+      // remove tree-toggle button and children list
+      if (!parent.children().length) {
+        parent.parent().find('div.treetoggle').remove();
+        parent.remove();
+      }
+
+      return true;
+    }
+
+    return false;
+  }
+
+  /**
+   * (Re-)read tree data from DOM
+   */
+  function update_data()
+  {
+    data = walk_list(container, 0);
+  }
+
+  /**
+   * Apply the 'collapsed' status of the data node to the corresponding DOM element(s)
+   */
+  function update_dom(node)
+  {
+    var li = id2dom(node.id, true);
+    li.attr('aria-expanded', node.collapsed ? 'false' : 'true');
+    li.children('ul').first()[(node.collapsed ? 'hide' : 'show')]();
+    li.children('div.treetoggle').removeClass('collapsed expanded').addClass(node.collapsed ? 'collapsed' : 'expanded');
+    me.triggerEvent('toggle', node);
+  }
+
+  /**
+   *
+   */
+  function reset(keep_content)
+  {
+    select('');
+
+    data = [];
+    indexbyid = {};
+    drag_active = false;
+
+    if (keep_content) {
+      if (draggable_opts) {
+        if (ui_draggable)
+          draggable('destroy');
+        draggable(draggable_opts);
+      }
+
+      if (droppable_opts) {
+        if (ui_droppable)
+          droppable('destroy');
+        droppable(droppable_opts);
+      }
+
+      update_data();
+    }
+    else {
+      container.html('');
+    }
+
+    reset_search();
+  }
+
+  /**
+   * 
+   */
+  function search(q, enter)
+  {
+    q = String(q).toLowerCase();
+
+    if (!q.length)
+      return reset_search();
+    else if (q == last_search && !enter)
+      return 0;
+
+    var hits = [];
+    var search_tree = function(items) {
+      $.each(items, function(i, node) {
+        var li, sli;
+        if (!node.virtual && !node.deleted && String(node.text).toLowerCase().indexOf(q) >= 0 && hits.indexOf(node.id) < 0) {
+          li = id2dom(node.id);
+
+          // skip already filtered nodes
+          if (li.data('filtered'))
+            return;
+
+          sli = $('<li>')
+            .attr('id', li.attr('id') + '--xsR')
+            .attr('class', li.attr('class'))
+            .addClass('searchresult__')
+            // append all elements like links and inputs, but not sub-trees
+            .append(li.children(':not(div.treetoggle,ul)').clone(true, true))
+            .appendTo(container);
+            hits.push(node.id);
+        }
+
+        if (node.children && node.children.length) {
+          search_tree(node.children);
+        }
+      });
+    };
+
+    // reset old search results
+    if (search_active) {
+      $(container).children('li.searchresult__').remove();
+      search_active = false;
+    }
+
+    // hide all list items
+    $(container).children('li').hide().removeClass('selected');
+
+    // search recursively in tree (to keep sorting order)
+    search_tree(data);
+    search_active = true;
+
+    me.triggerEvent('search', { query: q, last: last_search, count: hits.length, ids: hits, execute: enter||false });
+
+    last_search = q;
+
+    return hits.count;
+  }
+
+  /**
+   * 
+   */
+  function reset_search()
+  {
+    if (searchfield)
+      searchfield.val('');
+
+    $(container).children('li.searchresult__').remove();
+    $(container).children('li').filter(function() { return !$(this).data('filtered'); }).show();
+
+    search_active = false;
+
+    me.triggerEvent('search', { query: false, last: last_search });
+    last_search = '';
+
+    if (selection)
+      select(selection);
+  }
+
+  /**
+   *
+   */
+  function is_search()
+  {
+    return search_active;
+  }
+
+  /**
+   * Render the tree list from the internal data structure
+   */
+  function render()
+  {
+    if (me.triggerEvent('renderBefore', data) === false)
+      return;
+
+    // remove all child nodes
+    container.html('');
+
+    // render child nodes
+    for (var i=0; i < data.length; i++) {
+      data[i].level = 0;
+      render_node(data[i], container);
+    }
+
+    me.triggerEvent('renderAfter', container);
+  }
+
+  /**
+   * Render a specific node into the DOM list
+   */
+  function render_node(node, parent, replace)
+  {
+    if (node.deleted)
+      return;
+
+    var li = $('<li>')
+      .attr('id', p.id_prefix + (p.id_encode ? p.id_encode(node.id) : node.id))
+      .attr('role', 'treeitem')
+      .addClass((node.classes || []).join(' '))
+      .data('id', node.id);
+
+    if (replace) {
+      replace.replaceWith(li);
+      if (parent)
+        li.appendTo(parent);
+    }
+    else
+      li.appendTo(parent);
+
+    if (typeof node.html == 'string')
+      li.html(node.html);
+    else if (typeof node.html == 'object')
+      li.append(node.html);
+
+    if (!node.text)
+      node.text = li.children().first().text();
+
+    if (node.virtual)
+      li.addClass('virtual');
+    if (node.id == selection)
+      li.addClass('selected');
+
+    // add child list and toggle icon
+    if (node.children && node.children.length) {
+      li.attr('aria-expanded', node.collapsed ? 'false' : 'true');
+      $('<div class="treetoggle '+(node.collapsed ? 'collapsed' : 'expanded') + '">&nbsp;</div>').appendTo(li);
+      var ul = $('<ul>').appendTo(li).attr('class', node.childlistclass).attr('role', 'group');
+      if (node.collapsed)
+        ul.hide();
+
+      for (var i=0; i < node.children.length; i++) {
+        node.children[i].level = node.level + 1;
+        render_node(node.children[i], ul);
+      }
+    }
+
+    return li;
+  }
+
+  /**
+   * Recursively walk the DOM tree and build an internal data structure
+   * representing the skeleton of this tree list.
+   */
+  function walk_list(ul, level)
+  {
+    var result = [];
+    ul.children('li').each(function(i,e){
+      var state, li = $(e), sublist = li.children('ul');
+      var node = {
+        id: dom2id(li),
+        classes: String(li.attr('class')).split(' '),
+        virtual: li.hasClass('virtual'),
+        level: level,
+        html: li.children().first().get(0).outerHTML,
+        text: li.children().first().text(),
+        children: walk_list(sublist, level+1)
+      }
+
+      if (sublist.length) {
+        node.childlistclass = sublist.attr('class');
+      }
+      if (node.children.length) {
+        if (node.collapsed === undefined)
+          node.collapsed = sublist.css('display') == 'none';
+
+        // apply saved state
+        state = get_state(node.id, node.collapsed);
+        if (state !== undefined) {
+          node.collapsed = state;
+          sublist[(state?'hide':'show')]();
+        }
+
+        if (!li.children('div.treetoggle').length)
+          $('<div class="treetoggle '+(node.collapsed ? 'collapsed' : 'expanded') + '">&nbsp;</div>').appendTo(li);
+
+        li.attr('aria-expanded', node.collapsed ? 'false' : 'true');
+      }
+      if (li.hasClass('selected')) {
+        li.attr('aria-selected', 'true');
+        selection = node.id;
+      }
+
+      li.data('id', node.id);
+
+      // declare list item as treeitem
+      li.attr('role', 'treeitem').attr('aria-level', node.level+1);
+
+      // allow virtual nodes to receive focus
+      if (node.virtual) {
+        li.children('a:first').attr('tabindex', '0');
+      }
+
+      result.push(node);
+      indexbyid[node.id] = node;
+    });
+
+    ul.attr('role', level == 0 ? 'tree' : 'group');
+
+    return result;
+  }
+
+  /**
+   * Recursively walk the data tree and index nodes by their ID
+   */
+  function index_data(node)
+  {
+    if (node.id) {
+      indexbyid[node.id] = node;
+    }
+    for (var c=0; node.children && c < node.children.length; c++) {
+      index_data(node.children[c]);
+    }
+  }
+
+  /**
+   * Get the (stripped) node ID from the given DOM element
+   */
+  function dom2id(li)
+  {
+    var domid = String(li.attr('id')).replace(new RegExp('^' + (p.id_prefix) || '%'), '').replace(/--xsR$/, '');
+    return p.id_decode ? p.id_decode(domid) : domid;
+  }
+
+  /**
+   * Get the <li> element for the given node ID
+   */
+  function id2dom(id, real)
+  {
+    var domid = p.id_encode ? p.id_encode(id) : id,
+      suffix = search_active && !real ? '--xsR' : '';
+
+    return $('#' + p.id_prefix + domid + suffix, container);
+  }
+
+  /**
+   * Scroll the parent container to make the given list item visible
+   */
+  function scroll_to_node(li)
+  {
+    var scroller = container.parent(),
+      current_offset = scroller.scrollTop(),
+      rel_offset = li.offset().top - scroller.offset().top;
+
+    if (rel_offset < 0 || rel_offset + li.height() > scroller.height())
+      scroller.scrollTop(rel_offset + current_offset);
+  }
+
+  /**
+   * Save node collapse state to localStorage
+   */
+  function save_state(id, collapsed)
+  {
+    if (p.save_state && window.rcmail) {
+      var key = 'treelist-' + list_id;
+      if (!tree_state) {
+        tree_state = rcmail.local_storage_get_item(key, {});
+      }
+
+      if (tree_state[id] != collapsed) {
+        tree_state[id] = collapsed;
+        rcmail.local_storage_set_item(key, tree_state);
+      }
+    }
+  }
+
+  /**
+   * Read node collapse state from localStorage
+   */
+  function get_state(id)
+  {
+    if (p.save_state && window.rcmail) {
+      if (!tree_state) {
+        tree_state = rcmail.local_storage_get_item('treelist-' + list_id, {});
+      }
+      return tree_state[id];
+    }
+
+    return undefined;
+  }
+
+  /**
+   * Handler for keyboard events on treelist
+   */
+  function keypress(e)
+  {
+    var target = e.target || {},
+      keyCode = rcube_event.get_keycode(e);
+
+    if (!has_focus || target.nodeName == 'INPUT' && keyCode != 38 && keyCode != 40 || target.nodeName == 'TEXTAREA' || target.nodeName == 'SELECT')
+      return true;
+
+    switch (keyCode) {
+      case 38:
+      case 40:
+      case 63232: // 'up', in safari keypress
+      case 63233: // 'down', in safari keypress
+        var li = p.keyboard ? container.find(':focus').closest('li') : [];
+        if (li.length) {
+          focus_next(li, (mod = keyCode == 38 || keyCode == 63232 ? -1 : 1));
+        }
+        return rcube_event.cancel(e);
+
+      case 37: // Left arrow key
+      case 39: // Right arrow key
+        var id, node, li = container.find(':focus').closest('li');
+        if (li.length) {
+          id = dom2id(li);
+          node = indexbyid[id];
+          if (node && node.children.length && node.collapsed != (keyCode == 37))
+            toggle(id, rcube_event.get_modifier(e) == SHIFT_KEY);  // toggle subtree
+        }
+        return false;
+
+      case 9:  // Tab
+        if (p.keyboard && p.tabexit) {
+          // jump to last/first item to move focus away from the treelist widget by tab
+          var limit = rcube_event.get_modifier(e) == SHIFT_KEY ? 'first' : 'last';
+          focus_noscroll(container.find('li[role=treeitem]:has(a)')[limit]().find('a:'+limit));
+        }
+        break;
+    }
+
+    return true;
+  }
+
+  function focus_next(li, dir, from_child)
+  {
+    var mod = dir < 0 ? 'prev' : 'next',
+      next = li[mod](), limit, parent;
+
+    if (dir > 0 && !from_child && li.children('ul[role=group]:visible').length) {
+      li.children('ul').children('li:first').find('a:first').focus();
+    }
+    else if (dir < 0 && !from_child && next.children('ul[role=group]:visible').length) {
+      next.children('ul').children('li:last').find('a:first').focus();
+    }
+    else if (next.length && next.find('a:first').focus().length) {
+        // focused
+    }
+    else {
+      parent = li.parent().closest('li[role=treeitem]');
+      if (parent.length)
+        if (dir < 0) {
+          parent.find('a:first').focus();
+        }
+        else {
+          focus_next(parent, dir, true);
+        }
+    }
+  }
+
+  /**
+   * Focus the given element without scrolling the list container
+   */
+  function focus_noscroll(elem)
+  {
+    if (elem.length) {
+      var frame = container.parent().get(0) || { scrollTop:0 },
+        y = frame.scrollTop || frame.scrollY;
+      elem.focus();
+      frame.scrollTop = y;
+    }
+  }
+
+
+  ///// drag & drop support
+
+  /**
+   * When dragging starts, compute absolute bounding boxes of the list and it's items
+   * for faster comparisons while mouse is moving
+   */
+  function drag_start(force)
+  {
+    if (!force && drag_active)
+      return;
+
+    drag_active = true;
+
+    var li, item, height,
+      pos = container.offset();
+
+    body_scroll_top = bw.ie ? 0 : window.pageYOffset;
+    list_scroll_top = container.parent().scrollTop();
+    pos.top += list_scroll_top;
+
+    box_coords = {
+      x1: pos.left,
+      y1: pos.top,
+      x2: pos.left + container.width(),
+      y2: pos.top + container.height()
+    };
+
+    item_coords = [];
+    for (var id in indexbyid) {
+      li = id2dom(id);
+      item = li.children().first().get(0);
+      if (item && (height = item.offsetHeight)) {
+        pos = $(item).offset();
+        pos.top += list_scroll_top;
+        item_coords[id] = {
+          x1: pos.left,
+          y1: pos.top,
+          x2: pos.left + item.offsetWidth,
+          y2: pos.top + height,
+          on: id == autoexpand_item
+        };
+      }
+    }
+
+    // enable auto-scrolling of list container
+    if (container.height() > container.parent().height()) {
+      container.parent()
+        .mousemove(function(e) {
+          var scroll = 0,
+            mouse = rcube_event.get_mouse_pos(e);
+          mouse.y -= container.parent().offset().top;
+
+          if (mouse.y < 25 && list_scroll_top > 0) {
+            scroll = -1; // up
+          }
+          else if (mouse.y > container.parent().height() - 25) {
+            scroll = 1; // down
+          }
+
+          if (drag_active && scroll != 0) {
+            if (!scroll_timer)
+              scroll_timer = window.setTimeout(function(){ drag_scroll(scroll); }, p.scroll_delay);
+          }
+          else if (scroll_timer) {
+            window.clearTimeout(scroll_timer);
+            scroll_timer = null;
+          }
+        })
+        .mouseleave(function() {
+          if (scroll_timer) {
+            window.clearTimeout(scroll_timer);
+            scroll_timer = null;
+          }
+        });
+    }
+  }
+
+  /**
+   * Signal that dragging has stopped
+   */
+  function drag_end()
+  {
+    if (!drag_active)
+      return;
+
+    drag_active = false;
+    scroll_timer = null;
+
+    if (autoexpand_timer) {
+      clearTimeout(autoexpand_timer);
+      autoexpand_timer = null;
+      autoexpand_item = null;
+    }
+
+    $('li.droptarget', container).removeClass('droptarget');
+  }
+
+  /**
+   * Scroll list container in the given direction
+   */
+  function drag_scroll(dir)
+  {
+    if (!drag_active)
+      return;
+
+    var old_top = list_scroll_top;
+    container.parent().get(0).scrollTop += p.scroll_step * dir;
+    list_scroll_top = container.parent().scrollTop();
+    scroll_timer = null;
+
+    if (list_scroll_top != old_top)
+      scroll_timer = window.setTimeout(function(){ drag_scroll(dir); }, p.scroll_speed);
+  }
+
+  /**
+   * Determine if the given mouse coords intersect the list and one of its items
+   */
+  function intersects(mouse, highlight)
+  {
+    // offsets to compensate for scrolling while dragging a message
+    var boffset = bw.ie ? -document.documentElement.scrollTop : body_scroll_top,
+      moffset = container.parent().scrollTop(),
+      result = null;
+
+    mouse.top = mouse.y + moffset - boffset;
+
+    // no intersection with list bounding box
+    if (mouse.x < box_coords.x1 || mouse.x >= box_coords.x2 || mouse.top < box_coords.y1 || mouse.top >= box_coords.y2) {
+      // TODO: optimize performance for this operation
+      if (highlight)
+        $('li.droptarget', container).removeClass('droptarget');
+      return result;
+    }
+
+    // check intersection with visible list items
+    var id, pos, node;
+    for (id in item_coords) {
+      pos = item_coords[id];
+      if (mouse.x >= pos.x1 && mouse.x < pos.x2 && mouse.top >= pos.y1 && mouse.top < pos.y2) {
+        node = indexbyid[id];
+
+        // if the folder is collapsed, expand it after the configured time
+        if (node.children && node.children.length && node.collapsed && p.autoexpand && autoexpand_item != id) {
+          if (autoexpand_timer)
+            clearTimeout(autoexpand_timer);
+
+          autoexpand_item = id;
+          autoexpand_timer = setTimeout(function() {
+            expand(autoexpand_item);
+            drag_start(true);  // re-calculate item coords
+            autoexpand_item = null;
+            if (ui_droppable)
+              $.ui.ddmanager.prepareOffsets($.ui.ddmanager.current, null);
+          }, p.autoexpand);
+        }
+        else if (autoexpand_timer && autoexpand_item != id) {
+          clearTimeout(autoexpand_timer);
+          autoexpand_item = null;
+          autoexpand_timer = null;
+        }
+
+        // check if this item is accepted as drop target
+        if (p.check_droptarget(node)) {
+          if (highlight) {
+            id2dom(id).addClass('droptarget');
+            pos.on = true;
+          }
+          result = id;
+        }
+        else {
+          result = null;
+        }
+      }
+      else if (pos.on) {
+        id2dom(id).removeClass('droptarget');
+        pos.on = false;
+      }
+    }
+
+    return result;
+  }
+
+  /**
+   * Wrapper for jQuery.UI.droppable() activation on this widget
+   *
+   * @param object Options as passed to regular .droppable() function
+   */
+  function droppable(opts)
+  {
+    if (!opts) opts = {};
+
+    if ($.type(opts) == 'string') {
+      if (opts == 'destroy') {
+        ui_droppable = null;
+      }
+      $('li:not(.virtual)', container).droppable(opts);
+      return this;
+    }
+
+    droppable_opts = opts;
+
+    var my_opts = $.extend({
+        greedy: true,
+        tolerance: 'pointer',
+        hoverClass: 'droptarget',
+        addClasses: false
+      }, opts);
+
+    my_opts.activate = function(e, ui) {
+      drag_start();
+      ui_droppable = ui;
+      if (opts.activate)
+        opts.activate(e, ui);
+    };
+
+    my_opts.deactivate = function(e, ui) {
+      drag_end();
+      ui_droppable = null;
+      if (opts.deactivate)
+        opts.deactivate(e, ui);
+    };
+
+    my_opts.over = function(e, ui) {
+      intersects(rcube_event.get_mouse_pos(e), false);
+      if (opts.over)
+        opts.over(e, ui);
+    };
+
+    $('li:not(.virtual)', container).droppable(my_opts);
+
+    return this;
+  }
+
+  /**
+   * Wrapper for jQuery.UI.draggable() activation on this widget
+   *
+   * @param object Options as passed to regular .draggable() function
+   */
+  function draggable(opts)
+  {
+    if (!opts) opts = {};
+
+    if ($.type(opts) == 'string') {
+      if (opts == 'destroy') {
+        ui_draggable = null;
+      }
+      $('li:not(.virtual)', container).draggable(opts);
+      return this;
+    }
+
+    draggable_opts = opts;
+
+    var my_opts = $.extend({
+        appendTo: 'body',
+        revert: 'invalid',
+        iframeFix: true,
+        addClasses: false,
+        cursorAt: {left: -20, top: 5},
+        create: function(e, ui) { ui_draggable = ui; },
+        helper: function(e) {
+          return $('<div>').attr('id', 'rcmdraglayer')
+            .text($.trim($(e.target).first().text()));
+        }
+      }, opts);
+
+    $('li:not(.virtual)', container).draggable(my_opts);
+
+    return this;
+  }
+}
+
+// use event processing functions from Roundcube's rcube_event_engine
+rcube_treelist_widget.prototype.addEventListener = rcube_event_engine.prototype.addEventListener;
+rcube_treelist_widget.prototype.removeEventListener = rcube_event_engine.prototype.removeEventListener;
+rcube_treelist_widget.prototype.triggerEvent = rcube_event_engine.prototype.triggerEvent;