is it Possible to apply ColorAnimationUsingKeyFrames to a DropShadowPanel?

Question

I'm using UWP and I'm trying to apply Color animation using Keyframes to a DropShadowPanel from the UWP Community Toolkit.

but I haven't been able to succeed so far I've been able to apply DoubleAnimation to BlurRadius Property and Opacity Property but everytime I try to apply Color animation my program breaks.

I also applied Color Animation to a Polygon Shape at my Canvas and it worked great, I'm using almost the same code, can somebody give me a hint please:

This is the code from my polygon it WORKS:

<ColorAnimationUsingKeyFrames Storyboard.TargetName="ChristmasStarUpperPosition"
                                                      Storyboard.TargetProperty="(Polygon.Fill).(SolidColorBrush.Color)"
                                                      RepeatBehavior="Forever"
                                                      AutoReverse="True">
                            <LinearColorKeyFrame Value="Silver" KeyTime="0:0:5"/>
                            <LinearColorKeyFrame Value="LightGray" KeyTime="0:0:2"/>
                            <SplineColorKeyFrame Value="Gray" KeyTime="0:0:2.5" KeySpline="0.6,0.0 0.9,0.00"/>
                            <DiscreteColorKeyFrame Value="Blue" KeyTime="0:0:3"/>
                            <LinearColorKeyFrame Value="Blue" KeyTime="0:0:5"/>
                            <LinearColorKeyFrame Value="LightBlue" KeyTime="0:0:2"/>
                            <SplineColorKeyFrame Value="DeepSkyBlue" KeyTime="0:0:2.5" KeySpline="0.6,0.0 0.9,0.00"/>
                            <DiscreteColorKeyFrame Value="Goldenrod" KeyTime="0:0:3"/>
                            <LinearColorKeyFrame Value="Goldenrod" KeyTime="0:0:5"/>
                        </ColorAnimationUsingKeyFrames>

and this is the code I'm trying to apply to my DropShadowPanel this code makes mas program fail at xaml level.

<ColorAnimationUsingKeyFrames Storyboard.TargetName="ChristmasBonusStarUpperDropShadowPolygonColor"
                                                      Storyboard.TargetProperty="(DropShadowPanel.Color).(SolidColorBrush.Color)"
                                                      RepeatBehavior="Forever"
                                                      AutoReverse="True">
                            <LinearColorKeyFrame Value="Silver" KeyTime="0:0:5"/>
                            <LinearColorKeyFrame Value="LightGray" KeyTime="0:0:2"/>
                            <SplineColorKeyFrame Value="Gray" KeyTime="0:0:2.5" KeySpline="0.6,0.0 0.9,0.00"/>
                            <DiscreteColorKeyFrame Value="Blue" KeyTime="0:0:3"/>
                            <LinearColorKeyFrame Value="Blue" KeyTime="0:0:5"/>
                            <LinearColorKeyFrame Value="LightBlue" KeyTime="0:0:2"/>
                            <SplineColorKeyFrame Value="DeepSkyBlue" KeyTime="0:0:2.5" KeySpline="0.6,0.0 0.9,0.00"/>
                            <DiscreteColorKeyFrame Value="Goldenrod" KeyTime="0:0:3"/>
                            <LinearColorKeyFrame Value="Goldenrod" KeyTime="0:0:5"/>
                        </ColorAnimationUsingKeyFrames>

hopefully someone can help me out!!!

Thanks!!!

Answer 1

Although the Color property is a dependency property, it merely acts like a proxy that updates the Color of an inner DropShadow (see code below) that comes from Windows.UI.Composition. A traditional XAML storyboard simply won't work.

private void OnColorChanged(Color newValue)
{
    if (_dropShadow != null)
    {
        _dropShadow.Color = newValue;
    }
}

But what you want can be easily achieved by using the new color animation API (i.e. CreateColorKeyFrameAnimation) from Composition. Here's an example for your particular case:

var compositor = Window.Current.Compositor;
var easeIn = compositor.CreateCubicBezierEasingFunction(new Vector2(0.6f, 0.0f), new Vector2(0.9f, 0.0f));
var linear = compositor.CreateLinearEasingFunction();

var colorAnimation = compositor.CreateColorKeyFrameAnimation();
// 0.0f means at 0% of the total duration of 5s, 0.2f means 20%, etc.
colorAnimation.InsertKeyFrame(0.0f, Colors.Red, linear);
colorAnimation.InsertKeyFrame(0.2f, Colors.DarkOrange, easeIn);
colorAnimation.InsertKeyFrame(0.4f, Colors.Green, linear);
colorAnimation.InsertKeyFrame(0.6f, Colors.Purple, easeIn);
colorAnimation.InsertKeyFrame(0.8f, Colors.DarkSlateGray, linear);
colorAnimation.InsertKeyFrame(1.0f, Colors.Black, linear);
colorAnimation.Duration = TimeSpan.FromSeconds(5);
colorAnimation.IterationBehavior = AnimationIterationBehavior.Forever;

// Note the control exposes the inner DropShadow property, and this is the property we want to animate
ChristmasBonusStarUpperDropShadowPolygon.DropShadow.StartAnimation("Color", colorAnimation);