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/* Copyright (c) 2006-2013 by OpenLayers Contributors (see authors.txt for
* full list of contributors). Published under the 2-clause BSD license.
* See license.txt in the OpenLayers distribution or repository for the
* full text of the license. */
/**
* @requires OpenLayers/Strategy.js
* @requires OpenLayers/Filter/Spatial.js
*/
/**
* Class: OpenLayers.Strategy.BBOX
* A simple strategy that reads new features when the viewport invalidates
* some bounds.
*
* Inherits from:
* - <OpenLayers.Strategy>
*/
OpenLayers.Strategy.BBOX = OpenLayers.Class(OpenLayers.Strategy, {
/**
* Property: bounds
* {<OpenLayers.Bounds>} The current data bounds (in the same projection
* as the layer - not always the same projection as the map).
*/
bounds: null,
/**
* Property: resolution
* {Float} The current data resolution.
*/
resolution: null,
/**
* APIProperty: ratio
* {Float} The ratio of the data bounds to the viewport bounds (in each
* dimension). Default is 2.
*/
ratio: 2,
/**
* Property: resFactor
* {Float} Optional factor used to determine when previously requested
* features are invalid. If set, the resFactor will be compared to the
* resolution of the previous request to the current map resolution.
* If resFactor > (old / new) and 1/resFactor < (old / new). If you
* set a resFactor of 1, data will be requested every time the
* resolution changes. If you set a resFactor of 3, data will be
* requested if the old resolution is 3 times the new, or if the new is
* 3 times the old. If the old bounds do not contain the new bounds
* new data will always be requested (with or without considering
* resFactor).
*/
resFactor: null,
/**
* Property: response
* {<OpenLayers.Protocol.Response>} The protocol response object returned
* by the layer protocol.
*/
response: null,
/**
* Constructor: OpenLayers.Strategy.BBOX
* Create a new BBOX strategy.
*
* Parameters:
* options - {Object} Optional object whose properties will be set on the
* instance.
*/
/**
* Method: activate
* Set up strategy with regard to reading new batches of remote data.
*
* Returns:
* {Boolean} The strategy was successfully activated.
*/
activate: function() {
var activated = OpenLayers.Strategy.prototype.activate.call(this);
if(activated) {
this.layer.events.on({
"moveend": this.update,
"refresh": this.update,
"visibilitychanged": this.update,
scope: this
});
this.update();
}
return activated;
},
/**
* Method: deactivate
* Tear down strategy with regard to reading new batches of remote data.
*
* Returns:
* {Boolean} The strategy was successfully deactivated.
*/
deactivate: function() {
var deactivated = OpenLayers.Strategy.prototype.deactivate.call(this);
if(deactivated) {
this.layer.events.un({
"moveend": this.update,
"refresh": this.update,
"visibilitychanged": this.update,
scope: this
});
}
return deactivated;
},
/**
* Method: update
* Callback function called on "moveend" or "refresh" layer events.
*
* Parameters:
* options - {Object} Optional object whose properties will determine
* the behaviour of this Strategy
*
* Valid options include:
* force - {Boolean} if true, new data must be unconditionally read.
* noAbort - {Boolean} if true, do not abort previous requests.
*/
update: function(options) {
var mapBounds = this.getMapBounds();
if (mapBounds !== null && ((options && options.force) ||
(this.layer.visibility && this.layer.calculateInRange() && this.invalidBounds(mapBounds)))) {
this.calculateBounds(mapBounds);
this.resolution = this.layer.map.getResolution();
this.triggerRead(options);
}
},
/**
* Method: getMapBounds
* Get the map bounds expressed in the same projection as this layer.
*
* Returns:
* {<OpenLayers.Bounds>} Map bounds in the projection of the layer.
*/
getMapBounds: function() {
if (this.layer.map === null) {
return null;
}
var bounds = this.layer.map.getExtent();
if(bounds && !this.layer.projection.equals(
this.layer.map.getProjectionObject())) {
bounds = bounds.clone().transform(
this.layer.map.getProjectionObject(), this.layer.projection
);
}
return bounds;
},
/**
* Method: invalidBounds
* Determine whether the previously requested set of features is invalid.
* This occurs when the new map bounds do not contain the previously
* requested bounds. In addition, if <resFactor> is set, it will be
* considered.
*
* Parameters:
* mapBounds - {<OpenLayers.Bounds>} the current map extent, will be
* retrieved from the map object if not provided
*
* Returns:
* {Boolean}
*/
invalidBounds: function(mapBounds) {
if(!mapBounds) {
mapBounds = this.getMapBounds();
}
var invalid = !this.bounds || !this.bounds.containsBounds(mapBounds);
if(!invalid && this.resFactor) {
var ratio = this.resolution / this.layer.map.getResolution();
invalid = (ratio >= this.resFactor || ratio <= (1 / this.resFactor));
}
return invalid;
},
/**
* Method: calculateBounds
*
* Parameters:
* mapBounds - {<OpenLayers.Bounds>} the current map extent, will be
* retrieved from the map object if not provided
*/
calculateBounds: function(mapBounds) {
if(!mapBounds) {
mapBounds = this.getMapBounds();
}
var center = mapBounds.getCenterLonLat();
var dataWidth = mapBounds.getWidth() * this.ratio;
var dataHeight = mapBounds.getHeight() * this.ratio;
this.bounds = new OpenLayers.Bounds(
center.lon - (dataWidth / 2),
center.lat - (dataHeight / 2),
center.lon + (dataWidth / 2),
center.lat + (dataHeight / 2)
);
},
/**
* Method: triggerRead
*
* Parameters:
* options - {Object} Additional options for the protocol's read method
* (optional)
*
* Returns:
* {<OpenLayers.Protocol.Response>} The protocol response object
* returned by the layer protocol.
*/
triggerRead: function(options) {
if (this.response && !(options && options.noAbort === true)) {
this.layer.protocol.abort(this.response);
this.layer.events.triggerEvent("loadend");
}
var evt = {filter: this.createFilter()};
this.layer.events.triggerEvent("loadstart", evt);
this.response = this.layer.protocol.read(
OpenLayers.Util.applyDefaults({
filter: evt.filter,
callback: this.merge,
scope: this
}, options));
},
/**
* Method: createFilter
* Creates a spatial BBOX filter. If the layer that this strategy belongs
* to has a filter property, this filter will be combined with the BBOX
* filter.
*
* Returns
* {<OpenLayers.Filter>} The filter object.
*/
createFilter: function() {
var filter = new OpenLayers.Filter.Spatial({
type: OpenLayers.Filter.Spatial.BBOX,
value: this.bounds,
projection: this.layer.projection
});
if (this.layer.filter) {
filter = new OpenLayers.Filter.Logical({
type: OpenLayers.Filter.Logical.AND,
filters: [this.layer.filter, filter]
});
}
return filter;
},
/**
* Method: merge
* Given a list of features, determine which ones to add to the layer.
* If the layer projection differs from the map projection, features
* will be transformed from the layer projection to the map projection.
*
* Parameters:
* resp - {<OpenLayers.Protocol.Response>} The response object passed
* by the protocol.
*/
merge: function(resp) {
this.layer.destroyFeatures();
if (resp.success()) {
var features = resp.features;
if(features && features.length > 0) {
var remote = this.layer.projection;
var local = this.layer.map.getProjectionObject();
if(!local.equals(remote)) {
var geom;
for(var i=0, len=features.length; i<len; ++i) {
geom = features[i].geometry;
if(geom) {
geom.transform(remote, local);
}
}
}
this.layer.addFeatures(features);
}
} else {
this.bounds = null;
}
this.response = null;
this.layer.events.triggerEvent("loadend", {response: resp});
},
CLASS_NAME: "OpenLayers.Strategy.BBOX"
});
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