1 /*
2  * Copyright 2023 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 #pragma once
18 
19 #include <utils/Timers.h>
20 
21 namespace android {
22 
23 /**
24  * Controls a slop logic. Slop here refers to an approach to try and drop insignificant input
25  * events. This is helpful in cases where unintentional input events may cause unintended outcomes,
26  * like scrolling a screen or keeping the screen awake.
27  *
28  * Current slop logic:
29  *      "If time since last event > Xns, then discard the next N values."
30  */
31 class SlopController final {
32 public:
33     SlopController(float slopThreshold, nsecs_t slopDurationNanos);
34 
35     /**
36      * Consumes an event with a given time and value for slop processing.
37      * Returns an amount <=value that should be consumed.
38      */
39     float consumeEvent(nsecs_t eventTime, float value);
40 
41 private:
42     bool shouldResetSlopTracking(nsecs_t eventTimeNanos, float value) const;
43 
44     /** The amount of event values ignored after an inactivity of the slop duration. */
45     const float mSlopThreshold;
46     /** The duration of inactivity that resets slop controlling. */
47     const nsecs_t mSlopDurationNanos;
48 
49     nsecs_t mLastEventTimeNanos = 0;
50     float mCumulativeValue = 0;
51     bool mHasSlopBeenMet = false;
52 };
53 
54 } // namespace android
55