WaveformLayer.updateLines.swift

private func updateLines(samples: [Float], yMidline: CGFloat) {
            
    let maxSampleMagnitude = max(dataProvider.summarySampleMax, -(dataProvider.summarySampleMin), Float.leastNonzeroMagnitude)
    let yScalingFactor = bounds.height / 2 / CGFloat(maxSampleMagnitude)
    var xPos: CGFloat = 0
    let cnt = samples.count
    var idx = 0
    let visibleDur = dataProvider.duration / Double(viewPort.zoom)
    let startTime = (Double(viewPort.startingXUnit) / Double(viewPort.xAxisUnits)) * dataProvider.duration
    
    while idx < cnt && xPos < bounds.maxX && idx < layers.count {
        let time = startTime + Double(xPos) / Double(viewPort.visibleWidth) * visibleDur
        let sample = dataProvider.sample(at: time)
        let layer = layers[idx]
        layer.isHidden = false
        
        let y = CGFloat(sample) * yScalingFactor
        layer.frame = CGRect(x: xPos, y: yMidline - y, width: 1, height: 2 * y)
        
        xPos += 1.0 / viewPort.screenScale
        idx += 1
    }
}