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Paul Ramirezbe9c5442024-07-10 00:12:41 +00001/**
2 * Copyright 2024 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 <chrono>
20#include <optional>
Paul Ramirezcf1b06e2024-08-01 17:11:58 +000021#include <vector>
Paul Ramirezbe9c5442024-07-10 00:12:41 +000022
23#include <input/Input.h>
24#include <input/InputTransport.h>
25#include <input/RingBuffer.h>
26#include <utils/Timers.h>
27
28namespace android {
29
30/**
31 * Resampler is an interface for resampling MotionEvents. Every resampling implementation
32 * must use this interface to enable resampling inside InputConsumer's logic.
33 */
34struct Resampler {
35 virtual ~Resampler() = default;
36
37 /**
38 * Tries to resample motionEvent at resampleTime. The provided resampleTime must be greater than
39 * the latest sample time of motionEvent. It is not guaranteed that resampling occurs at
40 * resampleTime. Interpolation may occur is futureSample is available. Otherwise, motionEvent
41 * may be resampled by another method, or not resampled at all. Furthermore, it is the
42 * implementer's responsibility to guarantee the following:
43 * - If resampling occurs, a single additional sample should be added to motionEvent. That is,
44 * if motionEvent had N samples before being passed to Resampler, then it will have N + 1
45 * samples by the end of the resampling. No other field of motionEvent should be modified.
46 * - If resampling does not occur, then motionEvent must not be modified in any way.
47 */
Paul Ramirez486ca6d2024-08-12 14:37:02 +000048 virtual void resampleMotionEvent(std::chrono::nanoseconds resampleTime,
Paul Ramirezbe9c5442024-07-10 00:12:41 +000049 MotionEvent& motionEvent,
50 const InputMessage* futureSample) = 0;
51};
52
53class LegacyResampler final : public Resampler {
54public:
55 /**
56 * Tries to resample `motionEvent` at `resampleTime` by adding a resampled sample at the end of
57 * `motionEvent` with eventTime equal to `resampleTime` and pointer coordinates determined by
58 * linear interpolation or linear extrapolation. An earlier `resampleTime` will be used if
59 * extrapolation takes place and `resampleTime` is too far in the future. If `futureSample` is
60 * not null, interpolation will occur. If `futureSample` is null and there is enough historical
61 * data, LegacyResampler will extrapolate. Otherwise, no resampling takes place and
62 * `motionEvent` is unmodified.
63 */
Paul Ramirez486ca6d2024-08-12 14:37:02 +000064 void resampleMotionEvent(std::chrono::nanoseconds resampleTime, MotionEvent& motionEvent,
Paul Ramirezbe9c5442024-07-10 00:12:41 +000065 const InputMessage* futureSample) override;
66
67private:
68 struct Pointer {
69 PointerProperties properties;
70 PointerCoords coords;
71 };
72
73 struct Sample {
74 std::chrono::nanoseconds eventTime;
Paul Ramirezcf1b06e2024-08-01 17:11:58 +000075 std::vector<Pointer> pointers;
76
77 std::vector<PointerCoords> asPointerCoords() const {
78 std::vector<PointerCoords> pointersCoords;
79 for (const Pointer& pointer : pointers) {
80 pointersCoords.push_back(pointer.coords);
81 }
82 return pointersCoords;
83 }
Paul Ramirezbe9c5442024-07-10 00:12:41 +000084 };
85
86 /**
87 * Keeps track of the previous MotionEvent deviceId to enable comparison between the previous
88 * and the current deviceId.
89 */
90 std::optional<DeviceId> mPreviousDeviceId;
91
92 /**
93 * Up to two latest samples from MotionEvent. Updated every time resampleMotionEvent is called.
94 * Note: We store up to two samples in order to simplify the implementation. Although,
95 * calculations are possible with only one previous sample.
96 */
97 RingBuffer<Sample> mLatestSamples{/*capacity=*/2};
98
99 /**
Paul Ramirezcf1b06e2024-08-01 17:11:58 +0000100 * Adds up to mLatestSamples.capacity() of motionEvent's latest samples to mLatestSamples. If
Paul Ramirezbe9c5442024-07-10 00:12:41 +0000101 * motionEvent has fewer samples than mLatestSamples.capacity(), then the available samples are
Paul Ramirezcf1b06e2024-08-01 17:11:58 +0000102 * added to mLatestSamples.
Paul Ramirezbe9c5442024-07-10 00:12:41 +0000103 */
104 void updateLatestSamples(const MotionEvent& motionEvent);
105
Paul Ramirezcf1b06e2024-08-01 17:11:58 +0000106 static Sample messageToSample(const InputMessage& message);
107
108 /**
109 * Checks if auxiliary sample has the same pointer properties of target sample. That is,
110 * auxiliary pointer IDs must appear in the same order as target pointer IDs, their toolType
111 * must match and be resampleable.
112 */
113 static bool pointerPropertiesResampleable(const Sample& target, const Sample& auxiliary);
114
Paul Ramirezbe9c5442024-07-10 00:12:41 +0000115 /**
Paul Ramirez486ca6d2024-08-12 14:37:02 +0000116 * Checks if there are necessary conditions to interpolate. For example, interpolation cannot
117 * take place if samples are too far apart in time. mLatestSamples must have at least one sample
118 * when canInterpolate is invoked.
Paul Ramirezbe9c5442024-07-10 00:12:41 +0000119 */
Paul Ramirez486ca6d2024-08-12 14:37:02 +0000120 bool canInterpolate(const InputMessage& futureSample) const;
Paul Ramirezbe9c5442024-07-10 00:12:41 +0000121
122 /**
Paul Ramirez486ca6d2024-08-12 14:37:02 +0000123 * Returns a sample interpolated between the latest sample of mLatestSamples and futureSample,
124 * if the conditions from canInterpolate are satisfied. Otherwise, returns nullopt.
125 * mLatestSamples must have at least one sample when attemptInterpolation is called.
Paul Ramirezbe9c5442024-07-10 00:12:41 +0000126 */
Paul Ramirez486ca6d2024-08-12 14:37:02 +0000127 std::optional<Sample> attemptInterpolation(std::chrono::nanoseconds resampleTime,
128 const InputMessage& futureSample) const;
129
130 /**
131 * Checks if there are necessary conditions to extrapolate. That is, there are at least two
132 * samples in mLatestSamples, and delta is bounded within a time interval.
133 */
134 bool canExtrapolate() const;
135
136 /**
137 * Returns a sample extrapolated from the two samples of mLatestSamples, if the conditions from
138 * canExtrapolate are satisfied. The returned sample either has eventTime equal to resampleTime,
139 * or an earlier time if resampleTime is too far in the future. If canExtrapolate returns false,
140 * this function returns nullopt.
141 */
142 std::optional<Sample> attemptExtrapolation(std::chrono::nanoseconds resampleTime) const;
143
144 inline static void addSampleToMotionEvent(const Sample& sample, MotionEvent& motionEvent);
Paul Ramirezbe9c5442024-07-10 00:12:41 +0000145};
Paul Ramirezcf1b06e2024-08-01 17:11:58 +0000146} // namespace android