// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
 
namespace System.Windows.Media.Animation
{
    /// <summary>
    /// Interface to be implemented by an object that can animate a property value.
    /// </summary>
    public interface IAnimation
    {
        /// <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>
        object GetCurrentValue(object defaultOriginValue, object defaultDestinationValue, AnimationClock animationClock);
    }
}