1 | /* Copyright (c) 2006-2010 by OpenLayers Contributors (see authors.txt for |
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2 | * full list of contributors). Published under the Clear BSD license. |
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3 | * See http://svn.openlayers.org/trunk/openlayers/license.txt for the |
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4 | * full text of the license. */ |
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5 | |
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6 | /** |
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7 | * @requires OpenLayers/Strategy.js |
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8 | * @requires OpenLayers/Filter.js |
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9 | */ |
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10 | |
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11 | /** |
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12 | * Class: OpenLayers.Strategy.Filter |
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13 | * Strategy for limiting features that get added to a layer by |
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14 | * evaluating a filter. The strategy maintains a cache of |
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15 | * all features until removeFeatures is called on the layer. |
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16 | * |
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17 | * Inherits from: |
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18 | * - <OpenLayers.Strategy> |
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19 | */ |
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20 | OpenLayers.Strategy.Filter = OpenLayers.Class(OpenLayers.Strategy, { |
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21 | |
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22 | /** |
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23 | * APIProperty: filter |
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24 | * {<OpenLayers.Filter>} Filter for limiting features sent to the layer. |
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25 | * Use the <setFilter> method to update this filter after construction. |
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26 | */ |
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27 | filter: null, |
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28 | |
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29 | /** |
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30 | * Property: cache |
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31 | * {Array(<OpenLayers.Feature.Vector>)} List of currently cached |
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32 | * features. |
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33 | */ |
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34 | cache: null, |
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35 | |
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36 | /** |
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37 | * Property: caching |
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38 | * {Boolean} The filter is currently caching features. |
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39 | */ |
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40 | caching: false, |
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41 | |
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42 | /** |
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43 | * Constructor: OpenLayers.Strategy.Filter |
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44 | * Create a new filter strategy. |
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45 | * |
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46 | * Parameters: |
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47 | * options - {Object} Optional object whose properties will be set on the |
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48 | * instance. Strategy must be constructed with at least a <filter> |
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49 | * property. |
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50 | */ |
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51 | initialize: function(options) { |
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52 | OpenLayers.Strategy.prototype.initialize.apply(this, [options]); |
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53 | if (!this.filter || !(this.filter instanceof OpenLayers.Filter)) { |
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54 | throw new Error("Filter strategy must be constructed with a filter"); |
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55 | } |
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56 | }, |
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57 | |
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58 | /** |
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59 | * APIMethod: activate |
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60 | * Activate the strategy. Register any listeners, do appropriate setup. |
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61 | * By default, this strategy automatically activates itself when a layer |
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62 | * is added to a map. |
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63 | * |
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64 | * Returns: |
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65 | * {Boolean} True if the strategy was successfully activated or false if |
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66 | * the strategy was already active. |
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67 | */ |
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68 | activate: function() { |
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69 | var activated = OpenLayers.Strategy.prototype.activate.apply(this, arguments); |
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70 | if (activated) { |
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71 | this.cache = []; |
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72 | this.layer.events.on({ |
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73 | "beforefeaturesadded": this.handleAdd, |
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74 | "beforefeaturesremoved": this.handleRemove, |
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75 | scope: this |
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76 | }); |
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77 | } |
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78 | return activated; |
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79 | }, |
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80 | |
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81 | /** |
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82 | * APIMethod: deactivate |
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83 | * Deactivate the strategy. Clear the feature cache. |
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84 | * |
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85 | * Returns: |
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86 | * {Boolean} True if the strategy was successfully deactivated or false if |
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87 | * the strategy was already inactive. |
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88 | */ |
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89 | deactivate: function() { |
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90 | this.cache = null; |
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91 | if (this.layer && this.layer.events) { |
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92 | this.layer.events.un({ |
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93 | "beforefeaturesadded": this.handleAdd, |
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94 | "beforefeaturesremoved": this.handleRemove, |
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95 | scope: this |
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96 | }); |
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97 | } |
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98 | return OpenLayers.Strategy.prototype.deactivate.apply(this, arguments); |
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99 | }, |
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100 | |
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101 | /** |
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102 | * Method: handleAdd |
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103 | */ |
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104 | handleAdd: function(event) { |
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105 | if (!this.caching) { |
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106 | var features = event.features; |
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107 | event.features = []; |
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108 | var feature; |
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109 | for (var i=0, ii=features.length; i<ii; ++i) { |
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110 | feature = features[i]; |
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111 | if (this.filter.evaluate(feature)) { |
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112 | event.features.push(feature); |
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113 | } else { |
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114 | this.cache.push(feature); |
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115 | } |
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116 | } |
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117 | } |
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118 | }, |
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119 | |
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120 | /** |
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121 | * Method: handleRemove |
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122 | */ |
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123 | handleRemove: function(event) { |
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124 | if (!this.caching) { |
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125 | this.cache = []; |
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126 | } |
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127 | }, |
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128 | |
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129 | /** |
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130 | * APIMethod: setFilter |
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131 | * Update the filter for this strategy. This will re-evaluate |
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132 | * any features on the layer and in the cache. Only features |
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133 | * for which filter.evalute(feature) returns true will be |
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134 | * added to the layer. Others will be cached by the strategy. |
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135 | * |
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136 | * Parameters: |
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137 | * filter - <OpenLayers.Filter> A filter for evaluating features. |
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138 | */ |
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139 | setFilter: function(filter) { |
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140 | this.filter = filter; |
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141 | var previousCache = this.cache; |
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142 | this.cache = []; |
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143 | // look through layer for features to remove from layer |
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144 | this.handleAdd({features: this.layer.features}); |
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145 | // cache now contains features to remove from layer |
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146 | if (this.cache.length > 0) { |
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147 | this.caching = true; |
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148 | this.layer.removeFeatures(this.cache.slice(), {silent: true}); |
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149 | this.caching = false; |
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150 | } |
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151 | // now look through previous cache for features to add to layer |
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152 | if (previousCache.length > 0) { |
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153 | var event = {features: previousCache}; |
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154 | this.handleAdd(event); |
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155 | // event has features to add to layer |
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156 | this.caching = true; |
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157 | this.layer.addFeatures(event.features, {silent: true}); |
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158 | this.caching = false; |
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159 | } |
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160 | }, |
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161 | |
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162 | CLASS_NAME: "OpenLayers.Strategy.Filter" |
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163 | |
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164 | }); |
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