roundProgress method

double roundProgress(double progress, { required FrameRate frameRate, })

Returns a "rounded" progress value according to the frameRate

Implementation

double roundProgress(double progress, {required FrameRate frameRate}) {
  var fps = frameRate.resolveFps(this.frameRate);
  if (fps == null) {
    return progress;
  }

  var noOffsetDurationFrames = durationFrames + 0.01;
  var totalFrameCount = (noOffsetDurationFrames / this.frameRate) * fps;
  // The epsilon absorbs the float error of adding back the 0.01 offset
  // (e.g. 69.99 - 10 + 0.01 == 59.99999999999999).
  var frameIndex = (totalFrameCount * progress + 1e-6).toInt();
  // Back to a composition frame, then to a progress relative to
  // durationFrames (which excludes the 0.01 offset) with the same expression
  // as the keyframes' progress, so that a frame lands exactly on the
  // keyframes placed on it.
  var frame = fps == this.frameRate
      ? frameIndex.toDouble()
      : frameIndex * this.frameRate / fps;
  var roundedProgress = min(frame / durationFrames, 1.0);
  assert(
    roundedProgress >= 0 && roundedProgress <= 1,
    'Progress is $roundedProgress',
  );
  return roundedProgress;
}