1/*
2 * Copyright (C) 2014 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
5 * in compliance with the License. You may obtain a copy of the License at
6 *
7 * http://www.apache.org/licenses/LICENSE-2.0
8 *
9 * Unless required by applicable law or agreed to in writing, software distributed under the License
10 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
11 * or implied. See the License for the specific language governing permissions and limitations under
12 * the License.
13 */
14package android.support.v17.leanback.animation;
15
16import static android.support.annotation.RestrictTo.Scope.LIBRARY_GROUP;
17
18import android.animation.TimeInterpolator;
19import android.support.annotation.RestrictTo;
20
21/**
22 * @hide
23 */
24@RestrictTo(LIBRARY_GROUP)
25public class LogDecelerateInterpolator implements TimeInterpolator {
26
27    int mBase;
28    int mDrift;
29    final float mLogScale;
30
31    public LogDecelerateInterpolator(int base, int drift) {
32        mBase = base;
33        mDrift = drift;
34
35        mLogScale = 1f / computeLog(1, mBase, mDrift);
36    }
37
38    static float computeLog(float t, int base, int drift) {
39        return (float) -Math.pow(base, -t) + 1 + (drift * t);
40    }
41
42    @Override
43    public float getInterpolation(float t) {
44        return computeLog(t, mBase, mDrift) * mLogScale;
45    }
46}
47