Please add LineRenderer color Tween

[tpnet]

Hope~

[KyryloKuzyk]

Can you please provide a code example? Either as an imaginary API or how you would animate it with Tween.Custom().

[tpnet]

Now I transition a LineRenderer to transparent, the code is as follows:

        var lineRenderer = mSetLineRenderer;
        var colorGradient = lineRenderer.colorGradient;
        Tween.Custom(1f, 0f, 1f, (v) =>
        {
            var alphaKeys = colorGradient.alphaKeys;
            for (var i = 0; i < alphaKeys.Length; i++)
            {
                var alphaKey = alphaKeys[i];
                alphaKey.alpha = v;
                alphaKeys[i] = alphaKey;
            }
            colorGradient.SetKeys(colorGradient.colorKeys, alphaKeys);
            lineRenderer.colorGradient = colorGradient;
        });

Now I transition a LineRenderer to other colors. The code is as follows:

        var correctGradient = mCorrectLineRenderer.colorGradient;
        var colorKeys = correctGradient.colorKeys;
        for (var i = 0; i < colorKeys.Length; i++)
        {
            var color = colorKeys[i].color;
            var index = i; 
            Tween.Custom(color, RightColor.colorKeys[0].color, 1f,
                (c) =>
                {
                    var updatedColorKeys = correctGradient.colorKeys;
                    updatedColorKeys[index].color = c;
                    correctGradient.SetKeys(updatedColorKeys, correctGradient.alphaKeys);
                    mCorrectLineRenderer.colorGradient = correctGradient;
                });
        }

It would be nice if the steps could be simplified. I see that DOTween provides an API that you can refer to:
DOColor(Color2 startValue, Color2 endValue, float duration)
Changes the target's color to the given one. Note that this method requires to also insert the start colors for the tween, since LineRenderers have no way to get them.
Color2 is a special DOTween struct which allows to store two colors in a single variable.

myLineRenderer.DOColor(new Color2(Color.white, Color.white), new Color2(Color.green, Color.black), 1);

[KyryloKuzyk]

DOTween's DOColor() method animates LineRenderer.startColor/endColor properties instead of colorGradient. Writing an equivalent animation in PrimeTween would require two separate animations:

var sequence = Sequence.Create()
    .Group(TweenExt.LineRendererStartColor(line, new(Color.white, Color.white, 1f)))
    .Group(TweenExt.LineRendererStartColor(line, new(Color.green, Color.black, 1f)));

It's also possible to extract the example you provided into a reusable LineRendererGradient() method, like this:

public static class TweenExt {
    public static Tween LineRendererStartColor(LineRenderer line, TweenSettings<Color> settings)
        => Tween.Custom(line, settings, (target, color) => target.startColor = color);

    public static Tween LineRendererEndColor(LineRenderer line, TweenSettings<Color> settings)
        => Tween.Custom(line, settings, (target, color) => target.endColor = color);

    public static Tween LineRendererGradient(LineRenderer line, TweenSettings<Color> settings) {
        return Tween.Custom(line, settings, (target, color) => {
            var gradient = target.colorGradient;
            var colorKeys = gradient.colorKeys;
            for (int i = 0; i < colorKeys.Length; i++) {
                colorKeys[i].color = color;
            }
            var alphaKeys = gradient.alphaKeys;
            for (int i = 0; i < alphaKeys.Length; i++) {
                alphaKeys[i].alpha = color.a;
            }
            gradient.SetKeys(colorKeys, alphaKeys);
            target.colorGradient = gradient;
        });
    }
}

I think it's reasonable to make startColor/endColor animations standard in PrimeTween, however I'm not sure about the gradient animation yet. Huge thanks for this proposal!