drawTick () {
    if (this.tickData === undefined || this.tickData.value.length < 1) return
    const maxlines = Math.floor(this.rectTick.height / this.layout.digit.height) - 1 // 屏幕最大能显示多少条记录
    const recs = this.tickData.value.length
    const beginIndex = recs > maxlines ? recs - maxlines : 0