AnimationHelper.cs

#region License

// From the CodeProject article by Ashley Davis: 
// http://www.codeproject.com/Articles/85603/A-WPF-custom-control-for-zooming-and-panning
// Licensed under the Code Project Open License (CPOL): 
// http://www.codeproject.com/info/cpol10.aspx

#endregion

using System;
using System.Windows;
using System.Windows.Media.Animation;

namespace GeminiGraphEditor
{
    /// <summary>
    ///     A helper class to simplify animation.
    /// </summary>
    internal static class AnimationHelper
    {
        /// <summary>
        ///     Starts an animation to a particular value on the specified dependency property.
        /// </summary>
        public static void StartAnimation(UIElement animatableElement,
            DependencyProperty dependencyProperty,
            double toValue,
            double animationDurationSeconds)
        {
            StartAnimation(animatableElement, dependencyProperty, toValue, animationDurationSeconds, null);
        }

        /// <summary>
        ///     Starts an animation to a particular value on the specified dependency property.
        ///     You can pass in an event handler to call when the animation has completed.
        /// </summary>
        public static void StartAnimation(UIElement animatableElement,
            DependencyProperty dependencyProperty,
            double toValue,
            double animationDurationSeconds,
            EventHandler completedEvent)
        {
            var fromValue = (double) animatableElement.GetValue(dependencyProperty);

            DoubleAnimation animation = new();
            animation.From = fromValue;
            animation.To = toValue;
            animation.Duration = TimeSpan.FromSeconds(animationDurationSeconds);

            animation.Completed += delegate(object sender, EventArgs e)
            {
                //
                // When the animation has completed bake final value of the animation
                // into the property.
                //
                animatableElement.SetValue(dependencyProperty, animatableElement.GetValue(dependencyProperty));
                CancelAnimation(animatableElement, dependencyProperty);

                if (completedEvent != null)
                    completedEvent(sender, e);
            };

            animation.Freeze();

            animatableElement.BeginAnimation(dependencyProperty, animation);
        }

        /// <summary>
        ///     Cancel any animations that are running on the specified dependency property.
        /// </summary>
        public static void CancelAnimation(UIElement animatableElement, DependencyProperty dependencyProperty)
        {
            animatableElement.BeginAnimation(dependencyProperty, null);
        }
    }
}