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/Spatial.js |
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9 | */ |
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10 | |
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11 | /** |
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12 | * Class: OpenLayers.Strategy.BBOX |
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13 | * A simple strategy that reads new features when the viewport invalidates |
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14 | * some bounds. |
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15 | * |
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16 | * Inherits from: |
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17 | * - <OpenLayers.Strategy> |
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18 | */ |
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19 | OpenLayers.Strategy.BBOX = OpenLayers.Class(OpenLayers.Strategy, { |
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20 | |
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21 | /** |
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22 | * Property: bounds |
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23 | * {<OpenLayers.Bounds>} The current data bounds (in the same projection |
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24 | * as the layer - not always the same projection as the map). |
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25 | */ |
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26 | bounds: null, |
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27 | |
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28 | /** |
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29 | * Property: resolution |
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30 | * {Float} The current data resolution. |
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31 | */ |
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32 | resolution: null, |
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33 | |
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34 | /** |
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35 | * APIProperty: ratio |
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36 | * {Float} The ratio of the data bounds to the viewport bounds (in each |
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37 | * dimension). Default is 2. |
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38 | */ |
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39 | ratio: 2, |
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40 | |
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41 | /** |
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42 | * Property: resFactor |
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43 | * {Float} Optional factor used to determine when previously requested |
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44 | * features are invalid. If set, the resFactor will be compared to the |
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45 | * resolution of the previous request to the current map resolution. |
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46 | * If resFactor > (old / new) and 1/resFactor < (old / new). If you |
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47 | * set a resFactor of 1, data will be requested every time the |
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48 | * resolution changes. If you set a resFactor of 3, data will be |
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49 | * requested if the old resolution is 3 times the new, or if the new is |
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50 | * 3 times the old. If the old bounds do not contain the new bounds |
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51 | * new data will always be requested (with or without considering |
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52 | * resFactor). |
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53 | */ |
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54 | resFactor: null, |
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55 | |
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56 | /** |
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57 | * Property: response |
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58 | * {<OpenLayers.Protocol.Response>} The protocol response object returned |
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59 | * by the layer protocol. |
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60 | */ |
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61 | response: null, |
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62 | |
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63 | /** |
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64 | * Constructor: OpenLayers.Strategy.BBOX |
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65 | * Create a new BBOX strategy. |
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66 | * |
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67 | * Parameters: |
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68 | * options - {Object} Optional object whose properties will be set on the |
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69 | * instance. |
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70 | */ |
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71 | initialize: function(options) { |
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72 | OpenLayers.Strategy.prototype.initialize.apply(this, [options]); |
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73 | }, |
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74 | |
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75 | /** |
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76 | * Method: activate |
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77 | * Set up strategy with regard to reading new batches of remote data. |
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78 | * |
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79 | * Returns: |
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80 | * {Boolean} The strategy was successfully activated. |
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81 | */ |
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82 | activate: function() { |
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83 | var activated = OpenLayers.Strategy.prototype.activate.call(this); |
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84 | if(activated) { |
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85 | this.layer.events.on({ |
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86 | "moveend": this.update, |
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87 | scope: this |
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88 | }); |
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89 | this.layer.events.on({ |
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90 | "refresh": this.update, |
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91 | scope: this |
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92 | }); |
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93 | } |
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94 | return activated; |
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95 | }, |
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96 | |
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97 | /** |
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98 | * Method: deactivate |
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99 | * Tear down strategy with regard to reading new batches of remote data. |
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100 | * |
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101 | * Returns: |
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102 | * {Boolean} The strategy was successfully deactivated. |
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103 | */ |
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104 | deactivate: function() { |
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105 | var deactivated = OpenLayers.Strategy.prototype.deactivate.call(this); |
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106 | if(deactivated) { |
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107 | this.layer.events.un({ |
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108 | "moveend": this.update, |
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109 | scope: this |
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110 | }); |
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111 | this.layer.events.un({ |
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112 | "refresh": this.update, |
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113 | scope: this |
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114 | }); |
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115 | } |
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116 | return deactivated; |
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117 | }, |
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118 | |
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119 | /** |
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120 | * Method: update |
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121 | * Callback function called on "moveend" or "refresh" layer events. |
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122 | * |
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123 | * Parameters: |
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124 | * options - {Object} An object with a property named "force", this |
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125 | * property references a boolean value indicating if new data |
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126 | * must be incondtionally read. |
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127 | */ |
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128 | update: function(options) { |
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129 | var mapBounds = this.getMapBounds(); |
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130 | if ((options && options.force) || this.invalidBounds(mapBounds)) { |
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131 | this.calculateBounds(mapBounds); |
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132 | this.resolution = this.layer.map.getResolution(); |
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133 | this.triggerRead(); |
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134 | } |
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135 | }, |
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136 | |
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137 | /** |
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138 | * Method: getMapBounds |
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139 | * Get the map bounds expressed in the same projection as this layer. |
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140 | * |
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141 | * Returns: |
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142 | * {<OpenLayers.Bounds>} Map bounds in the projection of the layer. |
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143 | */ |
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144 | getMapBounds: function() { |
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145 | var bounds = this.layer.map.getExtent(); |
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146 | if(!this.layer.projection.equals(this.layer.map.getProjectionObject())) { |
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147 | bounds = bounds.clone().transform( |
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148 | this.layer.map.getProjectionObject(), this.layer.projection |
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149 | ); |
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150 | } |
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151 | return bounds; |
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152 | }, |
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153 | |
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154 | /** |
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155 | * Method: invalidBounds |
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156 | * Determine whether the previously requested set of features is invalid. |
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157 | * This occurs when the new map bounds do not contain the previously |
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158 | * requested bounds. In addition, if <resFactor> is set, it will be |
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159 | * considered. |
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160 | * |
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161 | * Parameters: |
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162 | * mapBounds - {<OpenLayers.Bounds>} the current map extent, will be |
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163 | * retrieved from the map object if not provided |
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164 | * |
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165 | * Returns: |
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166 | * {Boolean} |
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167 | */ |
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168 | invalidBounds: function(mapBounds) { |
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169 | if(!mapBounds) { |
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170 | mapBounds = this.getMapBounds(); |
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171 | } |
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172 | var invalid = !this.bounds || !this.bounds.containsBounds(mapBounds); |
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173 | if(!invalid && this.resFactor) { |
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174 | var ratio = this.resolution / this.layer.map.getResolution(); |
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175 | invalid = (ratio >= this.resFactor || ratio <= (1 / this.resFactor)); |
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176 | } |
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177 | return invalid; |
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178 | }, |
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179 | |
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180 | /** |
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181 | * Method: calculateBounds |
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182 | * |
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183 | * Parameters: |
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184 | * mapBounds - {<OpenLayers.Bounds>} the current map extent, will be |
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185 | * retrieved from the map object if not provided |
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186 | */ |
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187 | calculateBounds: function(mapBounds) { |
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188 | if(!mapBounds) { |
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189 | mapBounds = this.getMapBounds(); |
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190 | } |
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191 | var center = mapBounds.getCenterLonLat(); |
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192 | var dataWidth = mapBounds.getWidth() * this.ratio; |
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193 | var dataHeight = mapBounds.getHeight() * this.ratio; |
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194 | this.bounds = new OpenLayers.Bounds( |
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195 | center.lon - (dataWidth / 2), |
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196 | center.lat - (dataHeight / 2), |
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197 | center.lon + (dataWidth / 2), |
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198 | center.lat + (dataHeight / 2) |
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199 | ); |
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200 | }, |
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201 | |
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202 | /** |
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203 | * Method: triggerRead |
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204 | * |
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205 | * Returns: |
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206 | * {<OpenLayers.Protocol.Response>} The protocol response object |
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207 | * returned by the layer protocol. |
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208 | */ |
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209 | triggerRead: function() { |
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210 | if (this.response) { |
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211 | this.layer.protocol.abort(this.response); |
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212 | this.layer.events.triggerEvent("loadend"); |
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213 | } |
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214 | this.layer.events.triggerEvent("loadstart"); |
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215 | this.response = this.layer.protocol.read({ |
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216 | filter: this.createFilter(), |
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217 | callback: this.merge, |
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218 | scope: this |
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219 | }); |
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220 | }, |
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221 | |
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222 | /** |
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223 | * Method: createFilter |
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224 | * Creates a spatial BBOX filter. If the layer that this strategy belongs |
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225 | * to has a filter property, this filter will be combined with the BBOX |
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226 | * filter. |
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227 | * |
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228 | * Returns |
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229 | * {<OpenLayers.Filter>} The filter object. |
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230 | */ |
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231 | createFilter: function() { |
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232 | var filter = new OpenLayers.Filter.Spatial({ |
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233 | type: OpenLayers.Filter.Spatial.BBOX, |
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234 | value: this.bounds, |
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235 | projection: this.layer.projection |
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236 | }); |
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237 | if (this.layer.filter) { |
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238 | filter = new OpenLayers.Filter.Logical({ |
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239 | type: OpenLayers.Filter.Logical.AND, |
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240 | filters: [this.layer.filter, filter] |
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241 | }); |
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242 | } |
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243 | return filter; |
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244 | }, |
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245 | |
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246 | /** |
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247 | * Method: merge |
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248 | * Given a list of features, determine which ones to add to the layer. |
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249 | * If the layer projection differs from the map projection, features |
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250 | * will be transformed from the layer projection to the map projection. |
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251 | * |
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252 | * Parameters: |
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253 | * resp - {<OpenLayers.Protocol.Response>} The response object passed |
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254 | * by the protocol. |
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255 | */ |
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256 | merge: function(resp) { |
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257 | this.layer.destroyFeatures(); |
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258 | var features = resp.features; |
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259 | if(features && features.length > 0) { |
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260 | var remote = this.layer.projection; |
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261 | var local = this.layer.map.getProjectionObject(); |
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262 | if(!local.equals(remote)) { |
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263 | var geom; |
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264 | for(var i=0, len=features.length; i<len; ++i) { |
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265 | geom = features[i].geometry; |
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266 | if(geom) { |
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267 | geom.transform(remote, local); |
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268 | } |
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269 | } |
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270 | } |
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271 | this.layer.addFeatures(features); |
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272 | } |
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273 | this.response = null; |
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274 | this.layer.events.triggerEvent("loadend"); |
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275 | }, |
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276 | |
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277 | CLASS_NAME: "OpenLayers.Strategy.BBOX" |
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278 | }); |
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