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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
*/
/**
* Class: OpenLayers.Strategy.Paging
* Strategy for vector feature paging
*
* Inherits from:
* - <OpenLayers.Strategy>
*/
OpenLayers.Strategy.Paging = OpenLayers.Class(OpenLayers.Strategy, {
/**
* Property: features
* {Array(<OpenLayers.Feature.Vector>)} Cached features.
*/
features: null,
/**
* Property: length
* {Integer} Number of features per page. Default is 10.
*/
length: 10,
/**
* Property: num
* {Integer} The currently displayed page number.
*/
num: null,
/**
* Property: paging
* {Boolean} The strategy is currently changing pages.
*/
paging: false,
/**
* Constructor: OpenLayers.Strategy.Paging
* Create a new paging strategy.
*
* Parameters:
* options - {Object} Optional object whose properties will be set on the
* instance.
*/
/**
* APIMethod: activate
* Activate the strategy. Register any listeners, do appropriate setup.
*
* Returns:
* {Boolean} The strategy was successfully activated.
*/
activate: function() {
var activated = OpenLayers.Strategy.prototype.activate.call(this);
if(activated) {
this.layer.events.on({
"beforefeaturesadded": this.cacheFeatures,
scope: this
});
}
return activated;
},
/**
* APIMethod: deactivate
* Deactivate the strategy. Unregister any listeners, do appropriate
* tear-down.
*
* Returns:
* {Boolean} The strategy was successfully deactivated.
*/
deactivate: function() {
var deactivated = OpenLayers.Strategy.prototype.deactivate.call(this);
if(deactivated) {
this.clearCache();
this.layer.events.un({
"beforefeaturesadded": this.cacheFeatures,
scope: this
});
}
return deactivated;
},
/**
* Method: cacheFeatures
* Cache features before they are added to the layer.
*
* Parameters:
* event - {Object} The event that this was listening for. This will come
* with a batch of features to be paged.
*/
cacheFeatures: function(event) {
if(!this.paging) {
this.clearCache();
this.features = event.features;
this.pageNext(event);
}
},
/**
* Method: clearCache
* Clear out the cached features. This destroys features, assuming
* nothing else has a reference.
*/
clearCache: function() {
if(this.features) {
for(var i=0; i<this.features.length; ++i) {
this.features[i].destroy();
}
}
this.features = null;
this.num = null;
},
/**
* APIMethod: pageCount
* Get the total count of pages given the current cache of features.
*
* Returns:
* {Integer} The page count.
*/
pageCount: function() {
var numFeatures = this.features ? this.features.length : 0;
return Math.ceil(numFeatures / this.length);
},
/**
* APIMethod: pageNum
* Get the zero based page number.
*
* Returns:
* {Integer} The current page number being displayed.
*/
pageNum: function() {
return this.num;
},
/**
* APIMethod: pageLength
* Gets or sets page length.
*
* Parameters:
* newLength - {Integer} Optional length to be set.
*
* Returns:
* {Integer} The length of a page (number of features per page).
*/
pageLength: function(newLength) {
if(newLength && newLength > 0) {
this.length = newLength;
}
return this.length;
},
/**
* APIMethod: pageNext
* Display the next page of features.
*
* Returns:
* {Boolean} A new page was displayed.
*/
pageNext: function(event) {
var changed = false;
if(this.features) {
if(this.num === null) {
this.num = -1;
}
var start = (this.num + 1) * this.length;
changed = this.page(start, event);
}
return changed;
},
/**
* APIMethod: pagePrevious
* Display the previous page of features.
*
* Returns:
* {Boolean} A new page was displayed.
*/
pagePrevious: function() {
var changed = false;
if(this.features) {
if(this.num === null) {
this.num = this.pageCount();
}
var start = (this.num - 1) * this.length;
changed = this.page(start);
}
return changed;
},
/**
* Method: page
* Display the page starting at the given index from the cache.
*
* Returns:
* {Boolean} A new page was displayed.
*/
page: function(start, event) {
var changed = false;
if(this.features) {
if(start >= 0 && start < this.features.length) {
var num = Math.floor(start / this.length);
if(num != this.num) {
this.paging = true;
var features = this.features.slice(start, start + this.length);
this.layer.removeFeatures(this.layer.features);
this.num = num;
// modify the event if any
if(event && event.features) {
// this.was called by an event listener
event.features = features;
} else {
// this was called directly on the strategy
this.layer.addFeatures(features);
}
this.paging = false;
changed = true;
}
}
}
return changed;
},
CLASS_NAME: "OpenLayers.Strategy.Paging"
});
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