nl_tokens: given a time return the corresponding x value for paper
pl_tokens: function time_x ( t ) { var self = this ; if ( t === null ) { return null ; } var delta = t - ui . capture_idx . <mask> ; if ( delta < 0 ) { console . log ( 'Negative delta for time ' + t ) ; } var pix = delta * ui . pix_per_sec / 1000 ; var x = margin [ 3 ] + pix ; return x ; }