Add resampling to InputConsumerNoResampling
Moved resampling into its own class and provided test coverage for it.
Bug: 297226446
Flag: EXEMPT refactor
Test: TEST=libinput_tests; m $TEST && $ANDROID_HOST_OUT/nativetest64/$TEST/$TEST --gtest_filter="*ResamplingTest*"
Change-Id: Ic6227b05120395c96643ab05e1cda373dba59e19
diff --git a/include/input/InputConsumerNoResampling.h b/include/input/InputConsumerNoResampling.h
index ae8de5f..65c2914 100644
--- a/include/input/InputConsumerNoResampling.h
+++ b/include/input/InputConsumerNoResampling.h
@@ -17,6 +17,7 @@
#pragma once
#include <input/InputTransport.h>
+#include <input/Resampler.h>
#include <utils/Looper.h>
namespace android {
@@ -47,13 +48,13 @@
/**
* Consumes input events from an input channel.
*
- * This is a re-implementation of InputConsumer that does not have resampling at the current moment.
- * A lot of the higher-level logic has been folded into this class, to make it easier to use.
- * In the legacy class, InputConsumer, the consumption logic was partially handled in the jni layer,
- * as well as various actions like adding the fd to the Choreographer.
+ * This is a re-implementation of InputConsumer. At the moment it only supports resampling for
+ * single pointer events. A lot of the higher-level logic has been folded into this class, to make
+ * it easier to use. In the legacy class, InputConsumer, the consumption logic was partially handled
+ * in the jni layer, as well as various actions like adding the fd to the Choreographer.
*
* TODO(b/297226446): use this instead of "InputConsumer":
- * - Add resampling to this class
+ * - Add resampling for multiple pointer events.
* - Allow various resampling strategies to be specified
* - Delete the old "InputConsumer" and use this class instead, renaming it to "InputConsumer".
* - Add tracing
@@ -64,8 +65,18 @@
*/
class InputConsumerNoResampling final {
public:
+ /**
+ * @param callbacks are used to interact with InputConsumerNoResampling. They're called whenever
+ * the event is ready to consume.
+ * @param looper needs to be sp and not shared_ptr because it inherits from
+ * RefBase
+ * @param resampler the resampling strategy to use. If null, no resampling will be
+ * performed.
+ */
explicit InputConsumerNoResampling(const std::shared_ptr<InputChannel>& channel,
- sp<Looper> looper, InputConsumerCallbacks& callbacks);
+ sp<Looper> looper, InputConsumerCallbacks& callbacks,
+ std::unique_ptr<Resampler> resampler);
+
~InputConsumerNoResampling();
/**
@@ -99,6 +110,7 @@
std::shared_ptr<InputChannel> mChannel;
sp<Looper> mLooper;
InputConsumerCallbacks& mCallbacks;
+ std::unique_ptr<Resampler> mResampler;
// Looper-related infrastructure
/**
diff --git a/include/input/Resampler.h b/include/input/Resampler.h
new file mode 100644
index 0000000..ff9c4b0
--- /dev/null
+++ b/include/input/Resampler.h
@@ -0,0 +1,115 @@
+/**
+ * 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>
+#include <input/InputTransport.h>
+#include <input/RingBuffer.h>
+#include <utils/Timers.h>
+
+namespace android {
+
+/**
+ * Resampler is an interface for resampling MotionEvents. Every resampling implementation
+ * must use this interface to enable resampling inside InputConsumer's logic.
+ */
+struct Resampler {
+ virtual ~Resampler() = default;
+
+ /**
+ * Tries to resample motionEvent at resampleTime. The provided resampleTime must be greater than
+ * the latest sample time of motionEvent. It is not guaranteed that resampling occurs at
+ * resampleTime. Interpolation may occur is futureSample is available. Otherwise, motionEvent
+ * may be resampled by another method, or not resampled at all. Furthermore, it is the
+ * implementer's responsibility to guarantee the following:
+ * - If resampling occurs, a single additional sample should be added to motionEvent. That is,
+ * if motionEvent had N samples before being passed to Resampler, then it will have N + 1
+ * samples by the end of the resampling. No other field of motionEvent should be modified.
+ * - If resampling does not occur, then motionEvent must not be modified in any way.
+ */
+ virtual void resampleMotionEvent(const std::chrono::nanoseconds resampleTime,
+ MotionEvent& motionEvent,
+ const InputMessage* futureSample) = 0;
+};
+
+class LegacyResampler final : public Resampler {
+public:
+ /**
+ * Tries to resample `motionEvent` at `resampleTime` by adding a resampled sample at the end of
+ * `motionEvent` with eventTime equal to `resampleTime` and pointer coordinates determined by
+ * linear interpolation or linear extrapolation. An earlier `resampleTime` will be used if
+ * extrapolation takes place and `resampleTime` is too far in the future. If `futureSample` is
+ * not null, interpolation will occur. If `futureSample` is null and there is enough historical
+ * data, LegacyResampler will extrapolate. Otherwise, no resampling takes place and
+ * `motionEvent` is unmodified.
+ */
+ void resampleMotionEvent(const std::chrono::nanoseconds resampleTime, MotionEvent& motionEvent,
+ const InputMessage* futureSample) override;
+
+private:
+ struct Pointer {
+ PointerProperties properties;
+ PointerCoords coords;
+ };
+
+ struct Sample {
+ std::chrono::nanoseconds eventTime;
+ Pointer pointer;
+
+ Sample(const std::chrono::nanoseconds eventTime, const PointerProperties& properties,
+ const PointerCoords& coords)
+ : eventTime{eventTime}, pointer{properties, coords} {}
+ };
+
+ /**
+ * Keeps track of the previous MotionEvent deviceId to enable comparison between the previous
+ * and the current deviceId.
+ */
+ std::optional<DeviceId> mPreviousDeviceId;
+
+ /**
+ * Up to two latest samples from MotionEvent. Updated every time resampleMotionEvent is called.
+ * Note: We store up to two samples in order to simplify the implementation. Although,
+ * calculations are possible with only one previous sample.
+ */
+ RingBuffer<Sample> mLatestSamples{/*capacity=*/2};
+
+ /**
+ * Adds up to mLatestSamples.capacity() of motionEvent's latest samples to mLatestSamples. (If
+ * motionEvent has fewer samples than mLatestSamples.capacity(), then the available samples are
+ * added to mLatestSamples.)
+ */
+ void updateLatestSamples(const MotionEvent& motionEvent);
+
+ /**
+ * May add a sample at the end of motionEvent with eventTime equal to resampleTime, and
+ * interpolated coordinates between the latest motionEvent sample and futureSample.
+ */
+ void interpolate(const std::chrono::nanoseconds resampleTime, MotionEvent& motionEvent,
+ const InputMessage& futureSample) const;
+
+ /**
+ * May add a sample at the end of motionEvent by extrapolating from the latest two samples. The
+ * added sample either has eventTime equal to resampleTime, or an earlier time if resampleTime
+ * is too far in the future.
+ */
+ void extrapolate(const std::chrono::nanoseconds resampleTime, MotionEvent& motionEvent) const;
+};
+} // namespace android
\ No newline at end of file