Merge "Reimplement Chromium's OneEuroFilter to InputConsumer" into main (b8591fb3) · Commits · e / os / android_frameworks_native

include/input/CoordinateFilter.h

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		/**
		* Copyright 2024 The Android Open Source Project
		*
		* Licensed under the Apache License, Version 2.0 (the "License");
		* you may not use this file except in compliance with the License.
		* You may obtain a copy of the License at
		*
		* http://www.apache.org/licenses/LICENSE-2.0
		*
		* Unless required by applicable law or agreed to in writing, software
		* distributed under the License is distributed on an "AS IS" BASIS,
		* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
		* See the License for the specific language governing permissions and
		* limitations under the License.
		*/

		#pragma once

		#include <chrono>

		#include <input/Input.h>
		#include <input/OneEuroFilter.h>

		namespace android {

		/**
		* Pair of OneEuroFilters that independently filter X and Y coordinates. Both filters share the same
		* constructor's parameters. The minimum cutoff frequency is the base cutoff frequency, that is, the
		* resulting cutoff frequency in the absence of signal's speed. Likewise, beta is a scaling factor
		* of the signal's speed that sets how much the signal's speed contributes to the resulting cutoff
		* frequency. The adaptive cutoff frequency criterion is f_c = f_c_min + β\|̇x_filtered\|
		*/
		class CoordinateFilter {
		public:
		explicit CoordinateFilter(float minCutoffFreq, float beta);

		/**
		* Filters in place only the AXIS_X and AXIS_Y fields from coords. Each call to filter must
		* provide a timestamp strictly greater than the timestamp of the previous call. The first time
		* this method is invoked no filtering takes place. Subsequent calls do overwrite `coords` with
		* filtered data.
		*
		* @param timestamp The timestamps at which to filter. It must be greater than the one passed in
		* the previous call.
		* @param coords Coordinates to be overwritten by the corresponding filtered coordinates.
		*/
		void filter(std::chrono::duration<float> timestamp, PointerCoords& coords);

		private:
		OneEuroFilter mXFilter;
		OneEuroFilter mYFilter;
		};

		} // namespace android
		No newline at end of file

include/input/OneEuroFilter.h

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		/**
		* Copyright 2024 The Android Open Source Project
		*
		* Licensed under the Apache License, Version 2.0 (the "License");
		* you may not use this file except in compliance with the License.
		* You may obtain a copy of the License at
		*
		* http://www.apache.org/licenses/LICENSE-2.0
		*
		* Unless required by applicable law or agreed to in writing, software
		* distributed under the License is distributed on an "AS IS" BASIS,
		* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
		* See the License for the specific language governing permissions and
		* limitations under the License.
		*/

		#pragma once

		#include <chrono>
		#include <optional>

		#include <input/Input.h>

		namespace android {

		/**
		* Low pass filter with adaptive low pass frequency based on the signal's speed. The signal's cutoff
		* frequency is determined by f_c = f_c_min + β\|̇x_filtered\|. Refer to
		* https://dl.acm.org/doi/10.1145/2207676.2208639 for details on how the filter works and how to
		* tune it.
		*/
		class OneEuroFilter {
		public:
		/**
		* Default cutoff frequency of the filtered signal's speed. 1.0 Hz is the value in the filter's
		* paper.
		*/
		static constexpr float kDefaultSpeedCutoffFreq = 1.0;

		OneEuroFilter() = delete;

		explicit OneEuroFilter(float minCutoffFreq, float beta,
		float speedCutoffFreq = kDefaultSpeedCutoffFreq);

		OneEuroFilter(const OneEuroFilter&) = delete;
		OneEuroFilter& operator=(const OneEuroFilter&) = delete;
		OneEuroFilter(OneEuroFilter&&) = delete;
		OneEuroFilter& operator=(OneEuroFilter&&) = delete;

		/**
		* Returns the filtered value of rawPosition. Each call to filter must provide a timestamp
		* strictly greater than the timestamp of the previous call. The first time the method is
		* called, it returns the value of rawPosition. Any subsequent calls provide a filtered value.
		*
		* @param timestamp The timestamp at which to filter. It must be strictly greater than the one
		* provided in the previous call.
		* @param rawPosition Position to be filtered.
		*/
		float filter(std::chrono::duration<float> timestamp, float rawPosition);

		private:
		/**
		* Minimum cutoff frequency. This is the constant term in the adaptive cutoff frequency
		* criterion. Units are Hertz.
		*/
		const float mMinCutoffFreq;

		/**
		* Slope of the cutoff frequency criterion. This is the term scaling the absolute value of the
		* filtered signal's speed. The data member is dimensionless, that is, it does not have units.
		*/
		const float mBeta;

		/**
		* Cutoff frequency of the signal's speed. This is the cutoff frequency applied to the filtering
		* of the signal's speed. Units are Hertz.
		*/
		const float mSpeedCutoffFreq;

		/**
		* The timestamp from the previous call. Units are seconds.
		*/
		std::optional<std::chrono::duration<float>> mPrevTimestamp;

		/**
		* The raw position from the previous call.
		*/
		std::optional<float> mPrevRawPosition;

		/**
		* The filtered velocity from the previous call. Units are position per second.
		*/
		std::optional<float> mPrevFilteredVelocity;

		/**
		* The filtered position from the previous call.
		*/
		std::optional<float> mPrevFilteredPosition;
		};

		} // namespace android

include/input/Resampler.h

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		@@ -19,11 +19,13 @@
		#include <array>
		#include <chrono>
		#include <iterator>
		#include <map>
		#include <optional>
		#include <vector>

		#include <android-base/logging.h>
		#include <ftl/mixins.h>
		#include <input/CoordinateFilter.h>
		#include <input/Input.h>
		#include <input/InputTransport.h>
		#include <input/RingBuffer.h>
		@@ -293,4 +295,43 @@ private:
		inline static void addSampleToMotionEvent(const Sample& sample, MotionEvent& motionEvent);
		};

		/**
		* Resampler that first applies the LegacyResampler resampling algorithm, then independently filters
		* the X and Y coordinates with a pair of One Euro filters.
		*/
		class FilteredLegacyResampler final : public Resampler {
		public:
		/**
		* Creates a resampler, using the given minCutoffFreq and beta to instantiate its One Euro
		* filters.
		*/
		explicit FilteredLegacyResampler(float minCutoffFreq, float beta);

		void resampleMotionEvent(std::chrono::nanoseconds requestedFrameTime, MotionEvent& motionEvent,
		const InputMessage* futureMessage) override;

		std::chrono::nanoseconds getResampleLatency() const override;

		private:
		LegacyResampler mResampler;

		/**
		* Minimum cutoff frequency of the value's low pass filter. Refer to OneEuroFilter class for a
		* more detailed explanation.
		*/
		const float mMinCutoffFreq;

		/**
		* Scaling factor of the adaptive cutoff frequency criterion. Refer to OneEuroFilter class for a
		* more detailed explanation.
		*/
		const float mBeta;

		/*
		* Note: an associative array with constant insertion and lookup times would be more efficient.
		* When this was implemented, there was no container with these properties.
		*/
		std::map<int32_t /pointerId/, CoordinateFilter> mFilteredPointers;
		};

		} // namespace android

libs/input/Android.bp

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		@@ -217,6 +217,7 @@ cc_library {
		],
		srcs: [
		"AccelerationCurve.cpp",
		"CoordinateFilter.cpp",
		"Input.cpp",
		"InputConsumer.cpp",
		"InputConsumerNoResampling.cpp",
		@@ -230,6 +231,7 @@ cc_library {
		"KeyLayoutMap.cpp",
		"MotionPredictor.cpp",
		"MotionPredictorMetricsManager.cpp",
		"OneEuroFilter.cpp",
		"PrintTools.cpp",
		"PropertyMap.cpp",
		"Resampler.cpp",

libs/input/CoordinateFilter.cpp

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		/**
		* Copyright 2024 The Android Open Source Project
		*
		* Licensed under the Apache License, Version 2.0 (the "License");
		* you may not use this file except in compliance with the License.
		* You may obtain a copy of the License at
		*
		* http://www.apache.org/licenses/LICENSE-2.0
		*
		* Unless required by applicable law or agreed to in writing, software
		* distributed under the License is distributed on an "AS IS" BASIS,
		* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
		* See the License for the specific language governing permissions and
		* limitations under the License.
		*/

		#define LOG_TAG "CoordinateFilter"

		#include <input/CoordinateFilter.h>

		namespace android {

		CoordinateFilter::CoordinateFilter(float minCutoffFreq, float beta)
		: mXFilter{minCutoffFreq, beta}, mYFilter{minCutoffFreq, beta} {}

		void CoordinateFilter::filter(std::chrono::duration<float> timestamp, PointerCoords& coords) {
		coords.setAxisValue(AMOTION_EVENT_AXIS_X, mXFilter.filter(timestamp, coords.getX()));
		coords.setAxisValue(AMOTION_EVENT_AXIS_Y, mYFilter.filter(timestamp, coords.getY()));
		}

		} // namespace android