1 /*
2  * Copyright (C) 2018 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License
15  */
16 
17 package com.android.systemui.doze.util
18 
19 import android.util.MathUtils
20 
21 private const val MILLIS_PER_MINUTES = 1000 * 60f
22 private const val BURN_IN_PREVENTION_PERIOD_Y = 521f
23 private const val BURN_IN_PREVENTION_PERIOD_X = 83f
24 private const val BURN_IN_PREVENTION_PERIOD_SCALE = 181f
25 private const val BURN_IN_PREVENTION_PERIOD_PROGRESS = 89f
26 
27 /**
28  * Returns the translation offset that should be used to avoid burn in at
29  * the current time (in pixels.)
30  *
31  * @param amplitude Maximum translation that will be interpolated.
32  * @param xAxis If we're moving on X or Y.
33  */
34 fun getBurnInOffset(amplitude: Int, xAxis: Boolean): Int {
35     return zigzag(System.currentTimeMillis() / MILLIS_PER_MINUTES,
36             amplitude.toFloat(),
37             if (xAxis) BURN_IN_PREVENTION_PERIOD_X else BURN_IN_PREVENTION_PERIOD_Y).toInt()
38 }
39 
40 /**
41  * Returns a progress offset (between 0f and 1.0f) that should be used to avoid burn in at
42  * the current time.
43  */
44 fun getBurnInProgressOffset(): Float {
45     return zigzag(System.currentTimeMillis() / MILLIS_PER_MINUTES,
46         1f, BURN_IN_PREVENTION_PERIOD_PROGRESS)
47 }
48 
49 /**
50  * Returns a value to scale a view in order to avoid burn in.
51  */
52 fun getBurnInScale(): Float {
53     return 0.8f + zigzag(System.currentTimeMillis() / MILLIS_PER_MINUTES,
54             0.2f, BURN_IN_PREVENTION_PERIOD_SCALE)
55 }
56 
57 /**
58  * Implements a continuous, piecewise linear, periodic zig-zag function
59  *
60  * Can be thought of as a linear approximation of abs(sin(x)))
61  *
62  * @param period period of the function, ie. zigzag(x + period) == zigzag(x)
63  * @param amplitude maximum value of the function
64  * @return a value between 0 and amplitude
65  */
66 private fun zigzag(x: Float, amplitude: Float, period: Float): Float {
67     val xprime = x % period / (period / 2)
68     val interpolationAmount = if (xprime <= 1) xprime else 2 - xprime
69     return MathUtils.lerp(0f, amplitude, interpolationAmount)
70 }