packages/SystemUI/src/com/android/systemui/recents/BakedBezierInterpolator.java

package com.android.systemui.recents;

import android.animation.TimeInterpolator;

/**
 * A pre-baked bezier-curved interpolator for quantum-paper transitions.
 */
public class BakedBezierInterpolator implements TimeInterpolator {
    public static final BakedBezierInterpolator INSTANCE = new BakedBezierInterpolator();

    /**
     * Use the INSTANCE variable instead of instantiating.
     */
    private BakedBezierInterpolator() {
        super();
    }

    /**
     * Lookup table values.
     * Generated using a Bezier curve from (0,0) to (1,1) with control points:
     * P0 (0,0)
     * P1 (0.4, 0)
     * P2 (0.2, 1.0)
     * P3 (1.0, 1.0)
     *
     * Values sampled with x at regular intervals between 0 and 1.
     *
     * These values were generated using:
     *   ./scripts/bezier_interpolator_values_gen.py 0.4 0.2
     */
    private static final float[] VALUES = new float[] {
        0.0f, 0.0002f, 0.0009f, 0.0019f, 0.0036f, 0.0059f, 0.0086f, 0.0119f, 0.0157f, 0.0209f,
        0.0257f, 0.0321f, 0.0392f, 0.0469f, 0.0566f, 0.0656f, 0.0768f, 0.0887f, 0.1033f, 0.1186f,
        0.1349f, 0.1519f, 0.1696f, 0.1928f, 0.2121f, 0.237f, 0.2627f, 0.2892f, 0.3109f, 0.3386f,
        0.3667f, 0.3952f, 0.4241f, 0.4474f, 0.4766f, 0.5f, 0.5234f, 0.5468f, 0.5701f, 0.5933f,
        0.6134f, 0.6333f, 0.6531f, 0.6698f, 0.6891f, 0.7054f, 0.7214f, 0.7346f, 0.7502f, 0.763f,
        0.7756f, 0.7879f, 0.8f, 0.8107f, 0.8212f, 0.8326f, 0.8415f, 0.8503f, 0.8588f, 0.8672f,
        0.8754f, 0.8833f, 0.8911f, 0.8977f, 0.9041f, 0.9113f, 0.9165f, 0.9232f, 0.9281f, 0.9328f,
        0.9382f, 0.9434f, 0.9476f, 0.9518f, 0.9557f, 0.9596f, 0.9632f, 0.9662f, 0.9695f, 0.9722f,
        0.9753f, 0.9777f, 0.9805f, 0.9826f, 0.9847f, 0.9866f, 0.9884f, 0.9901f, 0.9917f, 0.9931f,
        0.9944f, 0.9955f, 0.9964f, 0.9973f, 0.9981f, 0.9986f, 0.9992f, 0.9995f, 0.9998f, 1.0f, 1.0f
    };

    private static final float STEP_SIZE = 1.0f / (VALUES.length - 1);

    @Override
    public float getInterpolation(float input) {
        if (input >= 1.0f) {
            return 1.0f;
        }

        if (input <= 0f) {
            return 0f;
        }

        int position = Math.min(
                (int)(input * (VALUES.length - 1)),
                VALUES.length - 2);

        float quantized = position * STEP_SIZE;
        float difference = input - quantized;
        float weight = difference / STEP_SIZE;

        return VALUES[position] + weight * (VALUES[position + 1] - VALUES[position]);
    }

}