The QuerySource object stores a set of listeners and a set of queries.
It keeps the listeners aware of those queries that the source currently
contains, and it is then up to the listeners to decide what to do with
those queries in terms of displays.
Not used 2010-08 -- TimBL
@class QuerySource
@author jambo
function QuerySource () {
  /**
   * stores all of the queries currently held by this source,
   * indexed by ID number.
   */
  this.queries = []
  /**
   * stores the listeners for a query object.
   * @see TabbedContainer
   */
  this.listeners = []

  /**
   * add a Query object to the query source--It will be given an ID number
   * and a name, if it doesn't already have one. This subsequently adds the
   * query to all of the listeners the QuerySource knows about.
   */
  this.addQuery = function (q) {
    var i
    if (q.name === null || q.name === '') {
      q.name = 'Query #' + (this.queries.length + 1)
    }
    q.id = this.queries.length
    this.queries.push(q)
    for (i = 0; i < this.listeners.length; i++) {
      if (this.listeners[i] !== null) {
        this.listeners[i].addQuery(q)
      }
    }
  }

  /**
   * Remove a Query object from the source.  Tells all listeners to also
   * remove the query.
   */
  this.removeQuery = function (q) {
    var i
    for (i = 0; i < this.listeners.length; i++) {
      if (this.listeners[i] !== null) {
        this.listeners[i].removeQuery(q)
      }
    }
    if (this.queries[q.id] !== null) {
      delete this.queries[q.id]
    }
  }

  /**
   * adds a "Listener" to this QuerySource - that is, an object
   * which is capable of both adding and removing queries.
   * Currently, only the TabbedContainer class is added.
   * also puts all current queries into the listener to be used.
   */
  this.addListener = function (listener) {
    var i
    this.listeners.push(listener)
    for (i = 0; i < this.queries.length; i++) {
      if (this.queries[i] !== null) {
        listener.addQuery(this.queries[i])
      }
    }
  }
  /**
   * removes listener from the array of listeners, if it exists! Also takes
   * all of the queries from this source out of the listener.
   */
  this.removeListener = function (listener) {
    var i
    for (i = 0; i < this.queries.length; i++) {
      if (this.queries[i] !== null) {
        listener.removeQuery(this.queries[i])
      }
    }

    for (i = 0; i < this.listeners.length; i++) {
      if (this.listeners[i] === listener) {
        delete this.listeners[i]
      }
    }
  }
}