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

1 files changed, 115 insertions, 0 deletions

diff --git a/include/input/Resampler.h b/include/input/Resampler.h
new file mode 100644
index 0000000000..ff9c4b0868
--- /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