323 lines
11 KiB
C++
323 lines
11 KiB
C++
/*
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* Copyright (C) 2012 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#pragma once
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#include <input/Input.h>
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#include <utils/BitSet.h>
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#include <utils/Timers.h>
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#include <map>
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#include <set>
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namespace android {
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class VelocityTrackerStrategy;
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/*
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* Calculates the velocity of pointer movements over time.
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*/
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class VelocityTracker {
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public:
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enum class Strategy : int32_t {
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DEFAULT = -1,
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MIN = 0,
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IMPULSE = 0,
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LSQ1 = 1,
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LSQ2 = 2,
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LSQ3 = 3,
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WLSQ2_DELTA = 4,
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WLSQ2_CENTRAL = 5,
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WLSQ2_RECENT = 6,
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INT1 = 7,
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INT2 = 8,
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LEGACY = 9,
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MAX = LEGACY,
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};
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struct Estimator {
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static const size_t MAX_DEGREE = 4;
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// Estimator time base.
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nsecs_t time = 0;
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// Polynomial coefficients describing motion.
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std::array<float, MAX_DEGREE + 1> coeff{};
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// Polynomial degree (number of coefficients), or zero if no information is
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// available.
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uint32_t degree = 0;
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// Confidence (coefficient of determination), between 0 (no fit) and 1 (perfect fit).
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float confidence = 0;
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};
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/*
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* Contains all available velocity data from a VelocityTracker.
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*/
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struct ComputedVelocity {
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inline std::optional<float> getVelocity(int32_t axis, int32_t id) const {
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const auto& axisVelocities = mVelocities.find(axis);
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if (axisVelocities == mVelocities.end()) {
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return {};
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}
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const auto& axisIdVelocity = axisVelocities->second.find(id);
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if (axisIdVelocity == axisVelocities->second.end()) {
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return {};
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}
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return axisIdVelocity->second;
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}
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inline void addVelocity(int32_t axis, int32_t id, float velocity) {
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mVelocities[axis][id] = velocity;
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}
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private:
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std::map<int32_t /*axis*/, std::map<int32_t /*pointerId*/, float /*velocity*/>> mVelocities;
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};
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// Creates a velocity tracker using the specified strategy for each supported axis.
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// If strategy is not provided, uses the default strategy for the platform.
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// TODO(b/32830165): support axis-specific strategies.
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VelocityTracker(const Strategy strategy = Strategy::DEFAULT);
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~VelocityTracker();
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/** Return true if the axis is supported for velocity tracking, false otherwise. */
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static bool isAxisSupported(int32_t axis);
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// Resets the velocity tracker state.
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void clear();
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// Resets the velocity tracker state for a specific pointer.
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// Call this method when some pointers have changed and may be reusing
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// an id that was assigned to a different pointer earlier.
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void clearPointer(int32_t pointerId);
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// Adds movement information for a pointer for a specific axis
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void addMovement(nsecs_t eventTime, int32_t pointerId, int32_t axis, float position);
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// Adds movement information for all pointers in a MotionEvent, including historical samples.
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void addMovement(const MotionEvent* event);
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// Returns the velocity of the specified pointer id and axis in position units per second.
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// Returns empty optional if there is insufficient movement information for the pointer, or if
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// the given axis is not supported for velocity tracking.
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std::optional<float> getVelocity(int32_t axis, int32_t pointerId) const;
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// Returns a ComputedVelocity instance with all available velocity data, using the given units
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// (reference: units == 1 means "per millisecond"), and clamping each velocity between
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// [-maxVelocity, maxVelocity], inclusive.
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ComputedVelocity getComputedVelocity(int32_t units, float maxVelocity);
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// Gets an estimator for the recent movements of the specified pointer id for the given axis.
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// Returns false and clears the estimator if there is no information available
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// about the pointer.
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std::optional<Estimator> getEstimator(int32_t axis, int32_t pointerId) const;
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// Gets the active pointer id, or -1 if none.
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inline int32_t getActivePointerId() const { return mActivePointerId.value_or(-1); }
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private:
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nsecs_t mLastEventTime;
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BitSet32 mCurrentPointerIdBits;
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std::optional<int32_t> mActivePointerId;
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// An override strategy passed in the constructor to be used for all axes.
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// This strategy will apply to all axes, unless the default strategy is specified here.
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// When default strategy is specified, then each axis will use a potentially different strategy
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// based on a hardcoded mapping.
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const Strategy mOverrideStrategy;
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// Maps axes to their respective VelocityTrackerStrategy instances.
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// Note that, only axes that have had MotionEvents (and not all supported axes) will be here.
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std::map<int32_t /*axis*/, std::unique_ptr<VelocityTrackerStrategy>> mConfiguredStrategies;
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void configureStrategy(int32_t axis);
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// Generates a VelocityTrackerStrategy instance for the given Strategy type.
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// The `deltaValues` parameter indicates whether or not the created strategy should treat motion
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// values as deltas (and not as absolute values). This the parameter is applicable only for
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// strategies that support differential axes.
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static std::unique_ptr<VelocityTrackerStrategy> createStrategy(const Strategy strategy,
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bool deltaValues);
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};
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/*
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* Implements a particular velocity tracker algorithm.
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*/
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class VelocityTrackerStrategy {
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protected:
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VelocityTrackerStrategy() { }
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public:
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virtual ~VelocityTrackerStrategy() { }
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virtual void clearPointer(int32_t pointerId) = 0;
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virtual void addMovement(nsecs_t eventTime, int32_t pointerId, float position) = 0;
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virtual std::optional<VelocityTracker::Estimator> getEstimator(int32_t pointerId) const = 0;
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};
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/*
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* Velocity tracker algorithm based on least-squares linear regression.
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*/
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class LeastSquaresVelocityTrackerStrategy : public VelocityTrackerStrategy {
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public:
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enum class Weighting {
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// No weights applied. All data points are equally reliable.
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NONE,
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// Weight by time delta. Data points clustered together are weighted less.
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DELTA,
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// Weight such that points within a certain horizon are weighed more than those
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// outside of that horizon.
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CENTRAL,
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// Weight such that points older than a certain amount are weighed less.
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RECENT,
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};
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// Degree must be no greater than Estimator::MAX_DEGREE.
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LeastSquaresVelocityTrackerStrategy(uint32_t degree, Weighting weighting = Weighting::NONE);
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~LeastSquaresVelocityTrackerStrategy() override;
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void clearPointer(int32_t pointerId) override;
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void addMovement(nsecs_t eventTime, int32_t pointerId, float position) override;
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std::optional<VelocityTracker::Estimator> getEstimator(int32_t pointerId) const override;
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private:
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// Sample horizon.
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// We don't use too much history by default since we want to react to quick
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// changes in direction.
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static const nsecs_t HORIZON = 100 * 1000000; // 100 ms
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// Number of samples to keep.
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static const uint32_t HISTORY_SIZE = 20;
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struct Movement {
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nsecs_t eventTime;
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float position;
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};
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float chooseWeight(int32_t pointerId, uint32_t index) const;
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const uint32_t mDegree;
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const Weighting mWeighting;
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std::map<int32_t /*pointerId*/, size_t /*positionInArray*/> mIndex;
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std::map<int32_t /*pointerId*/, std::array<Movement, HISTORY_SIZE>> mMovements;
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};
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/*
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* Velocity tracker algorithm that uses an IIR filter.
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*/
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class IntegratingVelocityTrackerStrategy : public VelocityTrackerStrategy {
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public:
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// Degree must be 1 or 2.
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IntegratingVelocityTrackerStrategy(uint32_t degree);
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~IntegratingVelocityTrackerStrategy() override;
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void clearPointer(int32_t pointerId) override;
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void addMovement(nsecs_t eventTime, int32_t pointerId, float positions) override;
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std::optional<VelocityTracker::Estimator> getEstimator(int32_t pointerId) const override;
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private:
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// Current state estimate for a particular pointer.
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struct State {
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nsecs_t updateTime;
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uint32_t degree;
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float pos, vel, accel;
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};
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const uint32_t mDegree;
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BitSet32 mPointerIdBits;
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State mPointerState[MAX_POINTER_ID + 1];
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void initState(State& state, nsecs_t eventTime, float pos) const;
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void updateState(State& state, nsecs_t eventTime, float pos) const;
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void populateEstimator(const State& state, VelocityTracker::Estimator* outEstimator) const;
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};
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/*
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* Velocity tracker strategy used prior to ICS.
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*/
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class LegacyVelocityTrackerStrategy : public VelocityTrackerStrategy {
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public:
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LegacyVelocityTrackerStrategy();
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~LegacyVelocityTrackerStrategy() override;
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void clearPointer(int32_t pointerId) override;
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void addMovement(nsecs_t eventTime, int32_t pointerId, float position) override;
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std::optional<VelocityTracker::Estimator> getEstimator(int32_t pointerId) const override;
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private:
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// Oldest sample to consider when calculating the velocity.
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static const nsecs_t HORIZON = 200 * 1000000; // 100 ms
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// Number of samples to keep.
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static const uint32_t HISTORY_SIZE = 20;
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// The minimum duration between samples when estimating velocity.
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static const nsecs_t MIN_DURATION = 10 * 1000000; // 10 ms
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struct Movement {
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nsecs_t eventTime;
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float position;
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};
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std::map<int32_t /*pointerId*/, size_t /*positionInArray*/> mIndex;
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std::map<int32_t /*pointerId*/, std::array<Movement, HISTORY_SIZE>> mMovements;
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};
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class ImpulseVelocityTrackerStrategy : public VelocityTrackerStrategy {
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public:
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ImpulseVelocityTrackerStrategy(bool deltaValues);
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~ImpulseVelocityTrackerStrategy() override;
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void clearPointer(int32_t pointerId) override;
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void addMovement(nsecs_t eventTime, int32_t pointerId, float position) override;
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std::optional<VelocityTracker::Estimator> getEstimator(int32_t pointerId) const override;
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private:
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// Sample horizon.
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// We don't use too much history by default since we want to react to quick
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// changes in direction.
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static constexpr nsecs_t HORIZON = 100 * 1000000; // 100 ms
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// Number of samples to keep.
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static constexpr size_t HISTORY_SIZE = 20;
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struct Movement {
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nsecs_t eventTime;
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float position;
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};
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// Whether or not the input movement values for the strategy come in the form of delta values.
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// If the input values are not deltas, the strategy needs to calculate deltas as part of its
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// velocity calculation.
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const bool mDeltaValues;
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std::map<int32_t /*pointerId*/, size_t /*positionInArray*/> mIndex;
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std::map<int32_t /*pointerId*/, std::array<Movement, HISTORY_SIZE>> mMovements;
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};
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} // namespace android
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