private void Validate() { Debug.Assert(!_isValid); if (IsOffsetCumulative || IsAngleCumulative) { Point startPoint; Point startTangent; Point endPoint; Point endTangent; PathGeometry pathGeometry = PathGeometry; // Get values at the beginning of the path. pathGeometry.GetPointAtFractionLength(0.0, out startPoint, out startTangent); // Get values at the end of the path. pathGeometry.GetPointAtFractionLength(1.0, out endPoint, out endTangent); // Calculate difference. _accumulatingAngle = DoubleAnimationUsingPath.CalculateAngleFromTangentVector(endTangent.X, endTangent.Y) - DoubleAnimationUsingPath.CalculateAngleFromTangentVector(startTangent.X, startTangent.Y); _accumulatingOffset.X = endPoint.X - startPoint.X; _accumulatingOffset.Y = endPoint.Y - startPoint.Y; } _isValid = true; }
/// <summary> /// Calculates the value this animation believes should be the current value for the property. /// </summary> /// <param name="defaultOriginValue"> /// This value is the suggested origin value provided to the animation /// to be used if the animation does not have its own concept of a /// start value. If this animation is the first in a composition chain /// this value will be the snapshot value if one is available or the /// base property value if it is not; otherise this value will be the /// value returned by the previous animation in the chain with an /// animationClock that is not Stopped. /// </param> /// <param name="defaultDestinationValue"> /// This value is the suggested destination value provided to the animation /// to be used if the animation does not have its own concept of an /// end value. This value will be the base value if the animation is /// in the first composition layer of animations on a property; /// otherwise this value will be the output value from the previous /// composition layer of animations for the property. /// </param> /// <param name="animationClock"> /// This is the animationClock which can generate the CurrentTime or /// CurrentProgress value to be used by the animation to generate its /// output value. /// </param> /// <returns> /// The value this animation believes should be the current value for the property. /// </returns> protected override Matrix GetCurrentValueCore(Matrix defaultOriginValue, Matrix defaultDestinationValue, AnimationClock animationClock) { Debug.Assert(animationClock.CurrentState != ClockState.Stopped); PathGeometry pathGeometry = PathGeometry; if (pathGeometry == null) { return(defaultDestinationValue); } if (!_isValid) { Validate(); } Point pathPoint; Point pathTangent; pathGeometry.GetPointAtFractionLength(animationClock.CurrentProgress.Value, out pathPoint, out pathTangent); double angle = 0.0; if (DoesRotateWithTangent) { angle = DoubleAnimationUsingPath.CalculateAngleFromTangentVector(pathTangent.X, pathTangent.Y); } Matrix matrix = new Matrix(); double currentRepeat = (double)(animationClock.CurrentIteration - 1); if (currentRepeat > 0) { if (IsOffsetCumulative) { pathPoint = pathPoint + (_accumulatingOffset * currentRepeat); } if (DoesRotateWithTangent && IsAngleCumulative) { angle = angle + (_accumulatingAngle * currentRepeat); } } matrix.Rotate(angle); matrix.Translate(pathPoint.X, pathPoint.Y); if (IsAdditive) { return(Matrix.Multiply(matrix, defaultOriginValue)); } else { return(matrix); } }