/// <summary/>
protected override Rect GetCurrentValueCore(Rect baseFromValue, Rect baseToValue, AnimationClock animationClock) {
var progress = animationClock.CurrentProgress;
if (!progress.HasValue || Interpolator == null) {
return base.GetCurrentValueCore(baseFromValue, baseToValue, animationClock);
}
var fromValue = new Rect();
var toValue = new Rect();
var offset = new Rect();
var isValid = true;
if (From.HasValue) {
fromValue = From.Value;
if (To.HasValue) {
// from ... to
toValue = To.Value;
if (IsAdditive) {
offset = baseFromValue;
isValid = offset.IsValid();
}
} else if (By.HasValue) {
// from ... from+by
toValue = _add(fromValue, By.Value);
if (IsAdditive) {
offset = baseFromValue;
isValid = offset.IsValid();
}
} else {
// from ... base
toValue = baseToValue;
isValid = toValue.IsValid();
}
} else if (To.HasValue) {
// base ... to
fromValue = baseFromValue;
toValue = To.Value;
isValid = fromValue.IsValid();
} else if (By.HasValue) {
// base ... base+by
toValue = By.Value;
offset = baseFromValue;
isValid = offset.IsValid();
} else {
// base ... base
fromValue = baseFromValue;
toValue = baseToValue;
isValid = fromValue.IsValid() && toValue.IsValid();
}
if (!isValid) {
throw new InvalidOperationException("GetCurrentValueCore");
}
if (IsCumulative) {
var iteration = animationClock.CurrentIteration;
if (iteration.HasValue && iteration.Value > 1) {
offset = _add(_multiply(_subtract(toValue, fromValue), iteration.Value - 1), offset);
}
}
var interpolator = Interpolator ?? Interpolators.Linear;
var result = _add(_add(fromValue, _multiply(_subtract(toValue, fromValue), interpolator(progress.Value, 0.0, 1.0))), offset);
return result;
}