text: /* Copyright (c) 2006-2011 by OpenLayers Contributors (see authors.txt for 
   * full list of contributors). Published under the Clear BSD license.  
   * See http://svn.openlayers.org/trunk/openlayers/license.txt for the
   * full text of the license. */
  
  /**
   * @requires OpenLayers/Control.js
   * @requires OpenLayers/Control/Button.js
   */
  
  /**
   * Class: OpenLayers.Control.NavigationHistory
   * A navigation history control.  This is a meta-control, that creates two
   *     dependent controls: <previous> and <next>.  Call the trigger method
   *     on the <previous> and <next> controls to restore previous and next
   *     history states.  The previous and next controls will become active
   *     when there are available states to restore and will become deactive
   *     when there are no states to restore.
   *
   * Inherits from:
   *  - <OpenLayers.Control>
   */
  SuperMap.Control.NavigationHistory = SuperMap.Class(SuperMap.Control, {
  
      /**
       * Property: type
       * {String} Note that this control is not intended to be added directly
       *     to a control panel.  Instead, add the sub-controls previous and
       *     next.  These sub-controls are button type controls that activate
       *     and deactivate themselves.  If this parent control is added to
       *     a panel, it will act as a toggle.
       */
      type: SuperMap.Control.TYPE_TOGGLE,
  
      /**
       * APIProperty: previous
       * {<OpenLayers.Control>} A button type control whose trigger method restores
       *     the previous state managed by this control.
       */
      previous: null,
      
      /**
       * APIProperty: previousOptions
       * {Object} Set this property on the options argument of the constructor
       *     to set optional properties on the <previous> control.
       */
      previousOptions: null,
      
      /**
       * APIProperty: next
       * {<OpenLayers.Control>} A button type control whose trigger method restores
       *     the next state managed by this control.
       */
      next: null,
  
      /**
       * APIProperty: nextOptions
       * {Object} Set this property on the options argument of the constructor
       *     to set optional properties on the <next> control.
       */
      nextOptions: null,
  
      /**
       * APIProperty: limit
       * {Integer} Optional limit on the number of history items to retain.  If
       *     null, there is no limit.  Default is 50.
       */
      limit: 50,
  
      /**
       * APIProperty: autoActivate
       * {Boolean} Activate the control when it is added to a map.  Default is
       *     true.
       */
      autoActivate: true,
  
      /**
       * Property: clearOnDeactivate
       * {Boolean} Clear the history when the control is deactivated.  Default
       *     is false.
       */
      clearOnDeactivate: false,
  
      /**
       * Property: registry
       * {Object} An object with keys corresponding to event types.  Values
       *     are functions that return an object representing the current state.
       */
      registry: null,
  
      /**
       * Property: nextStack
       * {Array} Array of items in the history.
       */
      nextStack: null,
  
      /**
       * Property: previousStack
       * {Array} List of items in the history.  First item represents the current
       *     state.
       */
      previousStack: null,
      
      /**
       * Property: listeners
       * {Object} An object containing properties corresponding to event types.
       *     This object is used to configure the control and is modified on
       *     construction.
       */
      listeners: null,
      
      /**
       * Property: restoring
       * {Boolean} Currently restoring a history state.  This is set to true
       *     before calling restore and set to false after restore returns.
       */
      restoring: false,
      
      /**
       * Constructor: OpenLayers.Control.NavigationHistory 
       * 
       * Parameters:
       * options - {Object} An optional object whose properties will be used
       *     to extend the control.
       */
      initialize: function(options) {
      	SuperMap.Control.prototype.initialize.apply(this, [options]);
          
          this.registry = SuperMap.Util.extend({
              "moveend": this.getState
          }, this.registry);
          
          var previousOptions = {
              trigger: SuperMap.Function.bind(this.previousTrigger, this),
              displayClass: this.displayClass + " " + this.displayClass + "Previous"
          };
          SuperMap.Util.extend(previousOptions, this.previousOptions);
          this.previous = new SuperMap.Control.Button(previousOptions);
          
          var nextOptions = {
              trigger: SuperMap.Function.bind(this.nextTrigger, this),
              displayClass: this.displayClass + " " + this.displayClass + "Next"
          };
          SuperMap.Util.extend(nextOptions, this.nextOptions);
          this.next = new SuperMap.Control.Button(nextOptions);
  
          this.clear();
      },
      
      /**
       * Method: onPreviousChange
       * Called when the previous history stack changes.
       *
       * Parameters:
       * state - {Object} An object representing the state to be restored
       *     if previous is triggered again or null if no previous states remain.
       * length - {Integer} The number of remaining previous states that can
       *     be restored.
       */
      onPreviousChange: function(state, length) {
          if(state && !this.previous.active) {
              this.previous.activate();
          } else if(!state && this.previous.active) {
              this.previous.deactivate();
          }
      },
      
      /**
       * Method: onNextChange
       * Called when the next history stack changes.
       *
       * Parameters:
       * state - {Object} An object representing the state to be restored
       *     if next is triggered again or null if no next states remain.
       * length - {Integer} The number of remaining next states that can
       *     be restored.
       */
      onNextChange: function(state, length) {
          if(state && !this.next.active) {
              this.next.activate();
          } else if(!state && this.next.active) {
              this.next.deactivate();
          }
      },
      
      /**
       * APIMethod: destroy
       * Destroy the control.
       */
      destroy: function() {
      	SuperMap.Control.prototype.destroy.apply(this);
          this.previous.destroy();
          this.next.destroy();
          this.deactivate();
          for(var prop in this) {
              this[prop] = null;
          }
      },
      
      /** 
       * Method: setMap
       * Set the map property for the control and <previous> and <next> child
       *     controls.
       *
       * Parameters:
       * map - {<OpenLayers.Map>} 
       */
      setMap: function(map) {
          this.map = map;
          this.next.setMap(map);
          this.previous.setMap(map);
      },
  
      /**
       * Method: draw
       * Called when the control is added to the map.
       */
      draw: function() {
      	SuperMap.Control.prototype.draw.apply(this, arguments);
          this.next.draw();
          this.previous.draw();
      },
      
      /**
       * Method: previousTrigger
       * Restore the previous state.  If no items are in the previous history
       *     stack, this has no effect.
       *
       * Returns:
       * {Object} Item representing state that was restored.  Undefined if no
       *     items are in the previous history stack.
       */
      previousTrigger: function() {
          var current = this.previousStack.shift();
          var state = this.previousStack.shift();
          if(state != undefined) {
              this.nextStack.unshift(current);
              this.previousStack.unshift(state);
              this.restoring = true;
              this.restore(state);
              this.restoring = false;
              this.onNextChange(this.nextStack[0], this.nextStack.length);
              this.onPreviousChange(
                  this.previousStack[1], this.previousStack.length - 1
              );
          } else {
              this.previousStack.unshift(current);
          }
          return state;
      },
      
      /**
       * APIMethod: nextTrigger
       * Restore the next state.  If no items are in the next history
       *     stack, this has no effect.  The next history stack is populated
       *     as states are restored from the previous history stack.
       *
       * Returns:
       * {Object} Item representing state that was restored.  Undefined if no
       *     items are in the next history stack.
       */
      nextTrigger: function() {
          var state = this.nextStack.shift();
          if(state != undefined) {
              this.previousStack.unshift(state);
              this.restoring = true;
              this.restore(state);
              this.restoring = false;
              this.onNextChange(this.nextStack[0], this.nextStack.length);
              this.onPreviousChange(
                  this.previousStack[1], this.previousStack.length - 1
              );
          }
          return state;
      },
      
      /**
       * APIMethod: clear
       * Clear history.
       */
      clear: function() {
          this.previousStack = [];
          this.previous.deactivate();
          this.nextStack = [];
          this.next.deactivate();
      },
  
      /**
       * Method: getState
       * Get the current state and return it.
       *
       * Returns:
       * {Object} An object representing the current state.
       */
      getState: function() {
          return {
              center: this.map.getCenter(),
              resolution: this.map.getResolution(),
              projection: this.map.getProjectionObject(),
              units: this.map.getProjectionObject().getUnits() || 
                  this.map.units || this.map.baseLayer.units
          };
      },
  
      /**
       * Method: restore
       * Update the state with the given object.
       *
       * Parameters:
       * state - {Object} An object representing the state to restore.
       */
      restore: function(state) {
          var center, zoom;
          if (this.map.getProjectionObject() == state.projection) { 
              zoom = this.map.getZoomForResolution(state.resolution);
              center = state.center;
          } else {
              center = state.center.clone();
              center.transform(state.projection, this.map.getProjectionObject());
              var sourceUnits = state.units;
              var targetUnits = this.map.getProjectionObject().getUnits() || 
                  this.map.units || this.map.baseLayer.units;
              var resolutionFactor = sourceUnits && targetUnits ? 
                  SuperMap.INCHES_PER_UNIT[sourceUnits] / SuperMap.INCHES_PER_UNIT[targetUnits] : 1;
              zoom = this.map.getZoomForResolution(resolutionFactor*state.resolution); 
          }
          this.map.setCenter(center, zoom);
      },
      
      /**
       * Method: setListeners
       * Sets functions to be registered in the listeners object.
       */
      setListeners: function() {
          this.listeners = {};
          for(var type in this.registry) {
              this.listeners[type] = SuperMap.Function.bind(function() {
                  if(!this.restoring) {
                      var state = this.registry[type].apply(this, arguments);
                      this.previousStack.unshift(state);
                      if(this.previousStack.length > 1) {
                          this.onPreviousChange(
                              this.previousStack[1], this.previousStack.length - 1
                          );
                      }
                      if(this.previousStack.length > (this.limit + 1)) {
                          this.previousStack.pop();
                      }
                      if(this.nextStack.length > 0) {
                          this.nextStack = [];
                          this.onNextChange(null, 0);
                      }
                  }
                  return true;
              }, this);
          }
      },
  
      /**
       * APIMethod: activate
       * Activate the control.  This registers any listeners.
       *
       * Returns:
       * {Boolean} Control successfully activated.
       */
      activate: function() {
          var activated = false;
          if(this.map) {
              if(SuperMap.Control.prototype.activate.apply(this)) {
                  if(this.listeners == null) {
                      this.setListeners();
                  }
                  for(var type in this.listeners) {
                      this.map.events.register(type, this, this.listeners[type]);
                  }
                  activated = true;
                  if(this.previousStack.length == 0) {
                      this.initStack();
                  }
              }
          }
          return activated;
      },
      
      /**
       * Method: initStack
       * Called after the control is activated if the previous history stack is
       *     empty.
       */
      initStack: function() {
          if(this.map.getCenter()) {
              this.listeners.moveend();
          }
      },
      
      /**
       * APIMethod: deactivate
       * Deactivate the control.  This unregisters any listeners.
       *
       * Returns:
       * {Boolean} Control successfully deactivated.
       */
      deactivate: function() {
          var deactivated = false;
          if(this.map) {
              if(SuperMap.Control.prototype.deactivate.apply(this)) {
                  for(var type in this.listeners) {
                      this.map.events.unregister(
                          type, this, this.listeners[type]
                      );
                  }
                  if(this.clearOnDeactivate) {
                      this.clear();
                  }
                  deactivated = true;
              }
          }
          return deactivated;
      },
      
      CLASS_NAME: "SuperMap.Control.NavigationHistory"
  });
  
  