openlayers/lib/OpenLayers/Strategy/Fixed.js

   1 /* Copyright (c) 2006-2008 MetaCarta, Inc., published under the Clear BSD
   2  * license.  See http://svn.openlayers.org/trunk/openlayers/license.txt for the
   3  * full text of the license. */
   4
   5 /**
   6  * @requires OpenLayers/Strategy.js
   7  */
   8
   9 /**
  10  * Class: OpenLayers.Strategy.Fixed
  11  * A simple strategy that requests features once and never requests new data.
  12  *
  13  * Inherits from:
  14  *  - <OpenLayers.Strategy>
  15  */
  16 OpenLayers.Strategy.Fixed = OpenLayers.Class(OpenLayers.Strategy, {
  17
  18     /**
  19      * APIProperty: preload
  20      * {Boolean} Load data before layer made visible. Enabling this may result
  21      *   in considerable overhead if your application loads many data layers
  22      *   that are not visible by default. Default is true.
  23      */
  24     preload: false,
  25
  26     /**
  27      * Constructor: OpenLayers.Strategy.Fixed
  28      * Create a new Fixed strategy.
  29      *
  30      * Parameters:
  31      * options - {Object} Optional object whose properties will be set on the
  32      *     instance.
  33      */
  34     initialize: function(options) {
  35         OpenLayers.Strategy.prototype.initialize.apply(this, [options]);
  36     },
  37
  38     /**
  39      * APIMethod: destroy
  40      * Clean up the strategy.
  41      */
  42     destroy: function() {
  43         OpenLayers.Strategy.prototype.destroy.apply(this, arguments);
  44     },
  45
  46     /**
  47      * Method: activate
  48      * Activate the strategy: load data or add listener to load when visible
  49      *
  50      * Returns:
  51      * {Boolean} True if the strategy was successfully activated or false if
  52      *      the strategy was already active.
  53      */
  54     activate: function() {
  55         if(OpenLayers.Strategy.prototype.activate.apply(this, arguments)) {
  56             this.layer.events.on({
  57                 "refresh": this.load,
  58                 scope: this
  59             });
  60             if(this.layer.visibility == true || this.preload) {
  61                 this.load();
  62             } else {
  63                 this.layer.events.on({
  64                     "visibilitychanged": this.load,
  65                     scope: this
  66                 });
  67             }
  68             return true;
  69         }
  70         return false;
  71     },
  72
  73     /**
  74      * Method: deactivate
  75      * Deactivate the strategy.  Undo what is done in <activate>.
  76      *
  77      * Returns:
  78      * {Boolean} The strategy was successfully deactivated.
  79      */
  80     deactivate: function() {
  81         var deactivated = OpenLayers.Strategy.prototype.deactivate.call(this);
  82         if(deactivated) {
  83             this.layer.events.un({
  84                 "refresh": this.load,
  85                 "visibilitychanged": this.load,
  86                 scope: this
  87             });
  88         }
  89         return deactivated;
  90     },
  91
  92     /**
  93      * Method: load
  94      * Tells protocol to load data and unhooks the visibilitychanged event
  95      *
  96      * Parameters:
  97      * options - {Object} options to pass to protocol read.
  98      */
  99     load: function(options) {
 100         this.layer.events.triggerEvent("loadstart");
 101         this.layer.protocol.read(OpenLayers.Util.applyDefaults({
 102             callback: this.merge,
 103             scope: this
 104         }, options));
 105         this.layer.events.un({
 106             "visibilitychanged": this.load,
 107             scope: this
 108         });
 109     },
 110
 111     /**
 112      * Method: merge
 113      * Add all features to the layer.
 114      */
 115     merge: function(resp) {
 116         this.layer.destroyFeatures();
 117         var features = resp.features;
 118         if (features && features.length > 0) {
 119             var remote = this.layer.projection;
 120             var local = this.layer.map.getProjectionObject();
 121             if(!local.equals(remote)) {
 122                 var geom;
 123                 for(var i=0, len=features.length; i<len; ++i) {
 124                     geom = features[i].geometry;
 125                     if(geom) {
 126                         geom.transform(remote, local);
 127                     }
 128                 }
 129             }
 130             this.layer.addFeatures(features);
 131         }
 132         this.layer.events.triggerEvent("loadend");
 133     },
 134
 135     CLASS_NAME: "OpenLayers.Strategy.Fixed"
 136 });