Unclear support for some Win2D effects with Composition APIs

Hello, I’m working with the Composition APIs and some Win2D effects and I’ve read the list of the available Win2D effects that are currently supported with the Composition APIs here.

From the list in that page (as well as this page) I can see that the GaussianBlurEffect is marked with the [NoComposition] attribute, so it shouldn’t be supported. Yet I can use this method without any problems (and I’m not sure why):

public static SpriteVisual GetAttachedBlur<T>(
    [NotNull] this T element, float blur, int ms) where T : FrameworkElement
{
    // Get the visual and the compositor
    Visual visual = element.GetVisual();
    Compositor compositor = visual.Compositor;

    // Create the blur effect and the effect factory
    GaussianBlurEffect blurEffect = new GaussianBlurEffect
    {
        Name = "Blur",
        BlurAmount = blur,
        BorderMode = EffectBorderMode.Hard,
        Optimization = EffectOptimization.Balanced,
        Source = new CompositionEffectSourceParameter("source")
    };
    CompositionEffectFactory effectFactory = compositor.CreateEffectFactory(blurEffect);

    // Setup the rest of the effect
    CompositionEffectBrush effectBrush = effectFactory.CreateBrush();
    effectBrush.SetSourceParameter("source", compositor.CreateBackdropBrush());

    // Assign the effect to a brush and display it
    SpriteVisual sprite = compositor.CreateSpriteVisual();
    sprite.Brush = effectBrush;
    sprite.Size = new Vector2((float)element.ActualWidth, (float)element.ActualHeight);
    ElementCompositionPreview.SetElementChildVisual(element, sprite);
    return sprite;
}

I mean, looking at the documentation, I would expect the code to fail, since the GaussianBlurEffect doesn’t seem to be supported. Then, I tried another effect (the DirectionalBlurEffect, which is also marked as not supported by the Composition APIs) and that failed (the CreateEffectFactory threw an exception. So my questions are:

• If both those effects are marked as [NoComposition], why does the GaussianBlurEffect actually work with the Composition APIs, and the DirectionalBlurEffect doesn’t? Is there another way to use those other effects, or is there a plan to support them as well in future Windows 10 releases?

Thanks for your help!

[sohchatt]

Here’s a list of effects that are currently tagged as NoComposition but are supported as of today:

• All BlendEffectModes except Dissolve (Fall Creator’s Update Insider)
• BorderEffect (Creator’s Update)
• ColorMatrixEffect (Creator’s Update)
• DistantDiffuseEffect (Anniversary Update)
• DistatntSpecularEffect (Anniversary Update)
• GaussianBlurEffect (Anniversary Update)
• LuminaceToAlphaEffect (Anniversary Update)
• PointDiffuseEffect (Anniversary Update)
• PointSpecularEffect(Anniversary Update)
• SpotDiffuseEffect (Anniversary Update)
• SpotSpecularEffect (Anniversary Update)

You should see updates to the Win2D documentation over the next few days.

You (and others) have a direct say in which effects we support next: please feel free to submit feedback (and upvote) about the specific Win2D effects you’d like to see in the Composition APIs.

[sohchatt]

This is a documentation bug on the Win2D page: GaussianBlurEffect is supported in Composition.

Thanks for your feedback; we will update the Win2D effect descriptions.