Source: widgets/SpwPrintTask.js

/**
 * @class spw.widgets.SpwPrintTask
 */
define(["dojo/_base/declare", "spw/api/SpwBaseWidget", "dojo/_base/lang", 
        "dojo/i18n!./nls/SpwCanvasPrinter",
        "spw/api/MessageManager", "esri/config", "spw/api/Printer"], 
		function(declare, SpwBaseWidget, lang, labels, 
				MessageManager, esriConfig, Printer){

	return declare("spw.widgets.SpwPrintTask", [SpwBaseWidget], /** @lends spw.widgets.SpwPrintTask.prototype */{
		
		printServerUrl: "http://sampleserver6.arcgisonline.com:80/arcgis/rest/services/Utilities/PrintingTools/GPServer/Export Web Map Task",
		labels: labels,

		generating: false,
		
		widgetTitle: labels.printLabel,
		iconClass: "spwMapPrinterIcon",
		
		_widgetTitle: "",
		_iconClass: "",

		onActivate: function(){
			if(this.generating){
				MessageManager.getInstance().notifyInfo(this.labels["alreadyPrinting"]);
			} else {
				this.generating = true;

				this._widgetTitle = this.get('widgetTitle');
				this.set('widgetTitle', this.labels.generating);
		    	
				this._iconClass = this.get('iconClass');
				this.set('iconClass', "generatingIcon");
				
				this.inherited(arguments);
				
				new Printer().getImagePrintTask(this.printServerUrl, 750, 625, lang.hitch(this, this.printResult), lang.hitch(this, this.printError));
			}
		},
		
		printResult: function(data){
			this.generating = false;

			this.set('widgetTitle', this._widgetTitle);
			this.set('iconClass', this._iconClass);

			window.open(data.url);
		},
		
		printError: function(error){
			this.generating = false;

			this.set('widgetTitle', this._widgetTitle);
			this.set('iconClass', this._iconClass);

			console.log(error);
		}
	});
});