Custom Transformers

warning

Due to the lack of sufficient experience and practical verification in this section, the API here may change at any time.

In practice, we find that not all properties are atomic. Some properties may be composed of smaller ones, for example:

1. Color: Intuitively, the RGB space contains the R, G, B axes; the YUV space contains the Y, U, V axes. Different spaces require different handling methods.
2. Coordinates: In 2D, composed of X and Y.

Additionally, some properties change in highly nonlinear ways or depend on specific contexts or data structures (such as path animations), making it difficult to achieve with simple linear interpolation.
We may also find it cumbersome to insert many identical handleFunctions repeatedly for a particular type of animation in .Milease(). Therefore,
we need custom transformers to define how properties interpolate or map between states, achieving more precise, natural, and convenient animation effects.

Usage

Writing a Transformer

public class MyTransformation : ITransformation
{
    public bool CanTranslate<E>()
    {
        var type = typeof(E);
        if (type == typeof(int))
        {
            // Assume I only handle int types here
            return true;
        }

        return false;
    }

    public MileaseHandleFunction<T, E> MakeTransformation<T, E>(BlendingMode blendingMode)
    {
        // Assume I actually do nothing here
        return e =>
        {
            var progress = e.Progress;
            
            var ani = e.Animation;
            var startValue = (ani.StartValue as int?)!;
            var toValue = (ani.ToValue as int?)!;

            var result = startValue + (toValue - startValue) * progress;
            e.Animation.ValueSetter.Invoke(e.Target,  (E)(object)result);
        };
    }
}

Registering a Transformer

TransformationManagerHolder.TransformationManager.Register(new MyTransformation());

After this, during Milease's animation building process, whenever no handleFunction is specified, it will try to use your registered ITransformation here.

Built-in State Transformers

For convenience, Milease comes with a set of built-in transformers.

Color Transformer: Milease includes a color interpolation scheme in the OKLCH space to provide visually smoother color transition animations.