private async Task RenderWaveformAsync(bool withDelay)
{
// Note: This function does not set CurrentWaveform to null to allow the old
// one to stay visible until the new calculation is complete (when called by InvalidateWaveform).
renderWaveformCts?.Cancel();
renderWaveformCts?.Dispose();
renderWaveformCts = new CancellationTokenSource();
try
{
IsLoading = true;
if (withDelay)
{
await Task.Delay(300, renderWaveformCts.Token);
}
if (audioFile == null) // no longer available
{
IsLoading = false;
return;
}
double viewLeft = sequencer.CurrentViewLeftPositionTime - MusicTimeOffset;
double viewRight = sequencer.CurrentViewRightPositionTime - MusicTimeOffset;
double padding = (viewRight - viewLeft) / 4; // use the width of one viewport on each side as padding
double waveformLeft = Math.Max(0, viewLeft - padding);
double waveformRight = viewRight + padding;
Waveform result = await WaveformGenerator.CreateWaveformAsync(audioFile.CreateStream(),
sequencer.TimePixelScale,
waveformLeft,
waveformRight,
renderWaveformCts.Token);
Debug.WriteLine($"Time per sample: {result.TimePerSample}, Sample count: {result.Minimums.Length}");
CurrentWaveform = result;
IsLoading = false;
}
catch (OperationCanceledException) { }
}
