function onTap ( event ) {

	            event.preventDefault();
	            event.stopPropagation();

	            tapSkipped = false;

	            if ( !isFullscreen ) {

	                if ( container.requestFullscreen ) { container.requestFullscreen(); }
	                if ( container.msRequestFullscreen ) { container.msRequestFullscreen(); }
	                if ( container.mozRequestFullScreen ) { container.mozRequestFullScreen(); }
	                if ( container.webkitRequestFullscreen ) { container.webkitRequestFullscreen( Element.ALLOW_KEYBOARD_INPUT ); }
	              
	                isFullscreen = true;

	            } else {

	                if ( document.exitFullscreen ) { document.exitFullscreen(); }
	                if ( document.msExitFullscreen ) { document.msExitFullscreen(); }
	                if ( document.mozCancelFullScreen ) { document.mozCancelFullScreen(); }
	                if ( document.webkitExitFullscreen ) { document.webkitExitFullscreen( ); }

	                isFullscreen = false;

	            }

	            this.style.backgroundImage = ( isFullscreen ) 
	                ? 'url("' + DataImage.FullscreenLeave + '")' 
	                : 'url("' + DataImage.FullscreenEnter + '")';

	        }
Create Fullscreen button
@return {HTMLSpanElement} - The dom element icon for fullscreen
@memberOf Widget
@instance
@fires Widget#panolens-viewer-handler