protected override ExpressionVariant EvaluateCore(TimeSpan now, ExpressionVariant currentValue)
{
var starting = ExpressionVariant.Create(_startingValue);
var ctx = new ExpressionEvaluationContext
{
Parameters = Parameters,
Target = TargetObject,
CurrentValue = currentValue,
FinalValue = _finalValue ?? starting,
StartingValue = starting,
ForeignFunctionInterface = BuiltInExpressionFfi.Instance
};
var elapsed = now - _startedAt;
var res = EvaluateImpl(elapsed, currentValue, ref ctx);
if (_iterationBehavior == AnimationIterationBehavior.Count &&
!_finished &&
elapsed > _totalDuration)
{
// Active check?
TargetObject.Compositor.RemoveFromClock(this);
_finished = true;
}
return(res);
}
private ExpressionVariant EvaluateImpl(TimeSpan elapsed, ExpressionVariant currentValue, ref ExpressionEvaluationContext ctx)
{
if (elapsed < _delayTime)
{
if (_delayBehavior == AnimationDelayBehavior.SetInitialValueBeforeDelay)
{
return(ExpressionVariant.Create(GetKeyFrame(ref ctx, _keyFrames[0])));
}
return(currentValue);
}
elapsed -= _delayTime;
var iterationNumber = elapsed.Ticks / _duration.Ticks;
if (_iterationBehavior == AnimationIterationBehavior.Count &&
iterationNumber >= _iterationCount)
{
return(ExpressionVariant.Create(GetKeyFrame(ref ctx, _keyFrames[_keyFrames.Length - 1])));
}
var evenIterationNumber = iterationNumber % 2 == 0;
elapsed = TimeSpan.FromTicks(elapsed.Ticks % _duration.Ticks);
var reverse =
_direction == PlaybackDirection.Alternate
? !evenIterationNumber
: _direction == PlaybackDirection.AlternateReverse
? evenIterationNumber
: _direction == PlaybackDirection.Reverse;
var iterationProgress = elapsed.TotalSeconds / _duration.TotalSeconds;
if (reverse)
{
iterationProgress = 1 - iterationProgress;
}
var left = new ServerKeyFrame <T>
{
Value = _startingValue
};
var right = _keyFrames[_keyFrames.Length - 1];
for (var c = 0; c < _keyFrames.Length; c++)
{
var kf = _keyFrames[c];
if (kf.Key < iterationProgress)
{
// this is the last frame
if (c == _keyFrames.Length - 1)
{
return(ExpressionVariant.Create(GetKeyFrame(ref ctx, kf)));
}
left = kf;
right = _keyFrames[c + 1];
break;
}
}
var keyProgress = Math.Max(0, Math.Min(1, (iterationProgress - left.Key) / (right.Key - left.Key)));
var easedKeyProgress = (float)right.EasingFunction.Ease(keyProgress);
if (float.IsNaN(easedKeyProgress) || float.IsInfinity(easedKeyProgress))
{
return(currentValue);
}
return(ExpressionVariant.Create(_interpolator.Interpolate(
GetKeyFrame(ref ctx, left),
GetKeyFrame(ref ctx, right),
easedKeyProgress
)));
}