nl_tokens: Calculate mouse position relative to top left of viewer container .
pl_tokens: function mousePosition ( event ) { var bounds = container . getBoundingClientRect ( ) ; var <mask> = { } ; // pageX / pageY needed for iOS pos . x = ( event . clientX || event . pageX ) - bounds . left ; pos . y = ( event . clientY || event . pageY ) - bounds . top ; return pos ; }