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/*
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License: LGPL as per: http://www.gnu.org/copyleft/lesser.html
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$Id$
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*/
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/**
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* Base Listener class that is instanciated by all objects which provide
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* event listeners.
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* @constructor
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* @author Cameron Shorter
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*/
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function Listener() {
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/** An array [params] of (listener, target). */
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this.listeners=new Array();
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/**
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* An array [params] of values. These values might not be used if the set/get
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* functions are overwritten.
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*/
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this.values=new Array();
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/**
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* Add a listener function which will be called when param is updated; The
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* listener function should usually be: paint(target).
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* @param listener The function to call when the parameter changes.
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* @param target The object which owns the listener function.
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* @param param Parameter name; if this parameter changes then an event is
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* sent to all interested listeners.
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*/
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this.addListener=function(param, listener, target) {
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if (window.logger) logger.logEvent("addListener: "+param,this.id,target.id);
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if(!this.listeners[param]){
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this.listeners[param]=new Array();
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}
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this.removeListener(param,listener,target);
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//for(var i=0;i<this.listeners[param].length;i++){
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// if(this.listeners[param][i][0]==listener && this.listeners[param][i][1]==target){
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// return;
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// alert("Listener.addListener again: target="+target.id);
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// }
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//}
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this.listeners[param].push(new Array(listener,target));
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}
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/**
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* Add a listener function at the start of the list.
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* @param listener The function to call when the parameter changes.
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* @param target The object which owns the listener function.
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* @param param Parameter name; if this parameter changes then an event is
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* sent to all interested listeners.
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*/
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this.addFirstListener=function(param, listener, target) {
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if (window.logger) logger.logEvent("addFirstListener: "+param,this.id,target.id);
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if(!this.listeners[param]){
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this.listeners[param]=new Array();
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}
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this.removeListener(param,listener,target);
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this.listeners[param].unshift(new Array(listener,target));
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}
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/**
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* Remove a listener so that it is not called anymore when a param changes.
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* @param listener The function to call when the parameter changes.
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* @param target The object which owns the listener function.
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* @param param Parameter name; if this parameter changes then an event is
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* sent to all interested listeners.
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*/
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this.removeListener=function(param,listener,target){
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if(this.listeners[param]){
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for(var i=0;i<this.listeners[param].length;i++){
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if(this.listeners[param][i][0]==listener && this.listeners[param][i][1]==target){
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for(var j=i;j<this.listeners[param].length-1;j++){
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this.listeners[param][j]=this.listeners[param][j+1];
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}
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this.listeners[param].pop();
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return;
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}
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}
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}
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}
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/**
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* Call all the listeners that have registered interest in this parameter
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* using addListener.
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* @param param The parameter that has changed.
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* @param value The new parameter value.
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*/
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this.callListeners=function(param,value) {
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if (this.listeners[param]){
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var count = this.listeners[param].length;
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for(var i=0;i<count;i++){
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if (window.logger) logger.logEvent(param,this.id,this.listeners[param][i][1].id,value);
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//this is listenerFunction(target,value)
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if (this.listeners[param][i][0]) {
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this.listeners[param][i][0](this.listeners[param][i][1],value);
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} else {
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alert("Listener error: param="+param+", target="+this.listeners[param][i][1].id+", callBackFunction="+this.listeners[param][i][0]);
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}
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}
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}
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}
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/**
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* Update parameter and call all interested listeners. This function may
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* be overloaded to store the parameter in a elsewhere (eg in an XML
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* document).
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* @param param The parameter to change.
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* @parma value The new value of the param.
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*/
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this.setParam=function(param,value) {
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this.values[param] = value;
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// Call all the interested listeners
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this.callListeners(param,value);
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}
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/**
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* Return the param value, or return null if it does not exist. This
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* function may be overloaded to store the param elsewhere (eg in
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* an XML document).
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* @param param The parameter to get.
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* @return The value of the param.
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*/
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this.getParam=function(param) {
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return this.values[param];
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}
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}
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