Add Neural Stylus Palm Detection Filter, with unittest.

This is a major change that adds an implementation of
NeuralStylusPalmDetectionFilter, along with a unittest for it.

The changes outside of that new file are to support the new
class added.

Note that no actual implementation of a model is included, and this
class is not instantiated or used in this change.

Bug: 1009290
Change-Id: Icac32a1a113b0ff83e307bccb3a3d0fc948bcc48
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1880414Reviewed-by: Michael Spang <spang@chromium.org>
Commit-Queue: Rob Schonberger <robsc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#710609}

ui/events/BUILD.gn

@@ -625,6 +625,7 @@ if (!is_ios) {
         "ozone/evdev/touch_event_converter_evdev_unittest.cc",
         "ozone/evdev/touch_filter/false_touch_finder_unittest.cc",
         "ozone/evdev/touch_filter/heuristic_stylus_palm_detection_filter_unittest.cc",
+        "ozone/evdev/touch_filter/neural_stylus_palm_detection_filter_unittest.cc",
         "ozone/evdev/touch_filter/neural_stylus_palm_detection_filter_util_unittest.cc",
         "ozone/evdev/touch_filter/open_palm_detection_filter_unittest.cc",
         "ozone/evdev/touch_filter/palm_detection_filter_factory_unittest.cc",

ui/events/ozone/BUILD.gn

@@ -122,6 +122,8 @@ if (use_ozone) {
         "evdev/touch_filter/horizontally_aligned_touch_noise_filter.h",
         "evdev/touch_filter/low_pressure_filter.cc",
         "evdev/touch_filter/low_pressure_filter.h",
+        "evdev/touch_filter/neural_stylus_palm_detection_filter.cc",
+        "evdev/touch_filter/neural_stylus_palm_detection_filter.h",
         "evdev/touch_filter/neural_stylus_palm_detection_filter_model.cc",
         "evdev/touch_filter/neural_stylus_palm_detection_filter_model.h",
         "evdev/touch_filter/neural_stylus_palm_detection_filter_util.cc",

ui/events/ozone/evdev/touch_filter/neural_stylus_palm_detection_filter.h

+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef UI_EVENTS_OZONE_EVDEV_TOUCH_FILTER_NEURAL_STYLUS_PALM_DETECTION_FILTER_H_
+#define UI_EVENTS_OZONE_EVDEV_TOUCH_FILTER_NEURAL_STYLUS_PALM_DETECTION_FILTER_H_
+
+#include <bitset>
+#include <cstdint>
+#include <deque>
+#include <vector>
+
+#include "base/time/time.h"
+#include "ui/events/ozone/evdev/event_device_info.h"
+#include "ui/events/ozone/evdev/touch_evdev_types.h"
+#include "ui/events/ozone/evdev/touch_filter/neural_stylus_palm_detection_filter_model.h"
+#include "ui/events/ozone/evdev/touch_filter/neural_stylus_palm_detection_filter_util.h"
+#include "ui/events/ozone/evdev/touch_filter/palm_detection_filter.h"
+#include "ui/events/ozone/evdev/touch_filter/shared_palm_detection_filter_state.h"
+#include "ui/gfx/geometry/point_f.h"
+
+namespace ui {
+
+// An implementation of PalmDetectionFilter that relies on a DNN implementation
+// to decide on palm detection. Requires a configured model as an argument.
+// Heuristics are added for handling short strokes
+class EVENTS_OZONE_EVDEV_EXPORT NeuralStylusPalmDetectionFilter
+    : public PalmDetectionFilter {
+ public:
+  // Takes ownership of the model.
+  NeuralStylusPalmDetectionFilter(
+      const EventDeviceInfo& devinfo,
+      std::unique_ptr<NeuralStylusPalmDetectionFilterModel> palm_model,
+      SharedPalmDetectionFilterState* shared_palm_state);
+  ~NeuralStylusPalmDetectionFilter() override;
+  void Filter(const std::vector<InProgressTouchEvdev>& touches,
+              base::TimeTicks time,
+              std::bitset<kNumTouchEvdevSlots>* slots_to_hold,
+              std::bitset<kNumTouchEvdevSlots>* slots_to_suppress) override;
+
+  static bool CompatibleWithNeuralStylusPalmDetectionFilter(
+      const EventDeviceInfo& devinfo);
+
+  const static int kFeaturesPerSample;
+  const static int kExtraFeaturesForNeighbor;
+
+ private:
+  std::string FilterNameForTesting() const override;
+
+  void FindNearestNeighborsWithin(
+      int neighbor_count,
+      float max_distance,
+      const PalmFilterStroke& stroke,
+      std::vector<std::pair<float, int>>* nearest_strokes) const;
+  void FindBiggestNeighborsWithin(
+      int neighbor_count,
+      float max_distance,
+      const PalmFilterStroke& stroke,
+      std::vector<std::pair<float, int>>* biggest_strokes) const;
+
+  bool DetectSpuriousStroke(const std::vector<float>& features,
+                            int tracking_id,
+                            float threshold) const;
+  // Extracts the feature vector for the specified stroke.
+  std::vector<float> ExtractFeatures(int tracking_id) const;
+  void AppendFeatures(const PalmFilterStroke& stroke,
+                      std::vector<float>* features) const;
+  void AppendFeaturesAsNeighbor(const PalmFilterStroke& stroke,
+                                float distance,
+                                std::vector<float>* features) const;
+
+  bool ShouldDecideStroke(const PalmFilterStroke& stroke) const;
+  bool IsHeuristicPalmStroke(const PalmFilterStroke& stroke) const;
+  void EraseOldStrokes(base::TimeTicks time);
+
+  std::bitset<kNumTouchEvdevSlots> is_palm_;
+  std::bitset<kNumTouchEvdevSlots> is_delay_;
+  std::map<int, PalmFilterStroke> strokes_;
+  int tracking_ids_[kNumTouchEvdevSlots];
+  const PalmFilterDeviceInfo palm_filter_dev_info_;
+  std::unique_ptr<NeuralStylusPalmDetectionFilterModel> model_;
+
+  const static char kFilterName[];
+  static const std::vector<int> kRequiredAbsMtCodes;
+
+  DISALLOW_COPY_AND_ASSIGN(NeuralStylusPalmDetectionFilter);
+};
+
+}  // namespace ui
+
+#endif  // UI_EVENTS_OZONE_EVDEV_TOUCH_FILTER_NEURAL_STYLUS_PALM_DETECTION_FILTER_H_

ui/events/ozone/evdev/touch_filter/neural_stylus_palm_detection_filter_model.h

@@ -28,8 +28,7 @@ struct EVENTS_OZONE_EVDEV_EXPORT NeuralStylusPalmDetectionFilterModelConfig {
   // Maximum distance of neighbor centroid, in millimeters.
   float max_neighbor_distance_in_mm = 0.0f;
 
-  base::TimeDelta max_dead_neighbor_time =
-      base::TimeDelta::FromMilliseconds(0.0);
+  base::TimeDelta max_dead_neighbor_time;
 
   // Minimum count of samples in a stroke for neural comparison.
   uint32_t min_sample_count = 0;
@@ -62,7 +61,7 @@ class EVENTS_OZONE_EVDEV_EXPORT NeuralStylusPalmDetectionFilterModel {
   // result.
   virtual float Inference(const std::vector<float>& features) const = 0;
 
-  virtual NeuralStylusPalmDetectionFilterModelConfig& config() const = 0;
+  virtual const NeuralStylusPalmDetectionFilterModelConfig& config() const = 0;
 };
 
 }  // namespace ui