Port Chromium OS touch noise filtering to Chromium

ui/events/ozone/evdev/touch_noise/single_position_touch_noise_filter.cc

+// Copyright 2015 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.
+
+#include "ui/events/ozone/evdev/touch_noise/single_position_touch_noise_filter.h"
+
+#include "base/logging.h"
+#include "base/strings/stringprintf.h"
+
+namespace ui {
+
+namespace {
+
+// Max squared distance between fingers for the fingers to be considered in the
+// same position.
+const int kSamePositionMaxDistance2 = 2 * 2;
+
+// Max squared movement of a finger before it's no longer considered noise.
+const int kNoiseMaxMovement2 = 2 * 2;
+
+// Min duration in milliseconds after which touches in the same position are
+// considered noise.
+const int kMinDurationMs = 2000;
+
+// Max duration in milliseconds to check for common positions with previous
+// touches.
+const int kMaxDurationMs = 4000;
+
+// Returns the squared distance between (|x1|, |y1|) and (|x2|, |y2|)
+int Distance2(int x1, int y1, int x2, int y2) {
+  int offset_x = x2 - x1;
+  int offset_y = y2 - y1;
+  return offset_x * offset_x + offset_y * offset_y;
+}
+
+}  // namespace
+
+SinglePositionTouchNoiseFilter::SinglePositionTouchNoiseFilter()
+    : tracked_touches_start_(0), tracked_touches_end_(0) {
+  for (size_t i = 0; i < kNumTouchEvdevSlots; ++i)
+    tracked_slots_[i] = kNumTrackedTouches;
+}
+
+void SinglePositionTouchNoiseFilter::Filter(
+    const std::vector<InProgressTouchEvdev>& touches,
+    base::TimeDelta time,
+    std::bitset<kNumTouchEvdevSlots>* slots_with_noise) {
+  // Forget old touches which will no longer be considered for overlap.
+  base::TimeDelta touch_cutoff =
+      time - base::TimeDelta::FromMilliseconds(kMaxDurationMs);
+  for (size_t i = tracked_touches_start_; i != tracked_touches_end_;
+       i = (i + 1) % kNumTrackedTouches) {
+    if (!tracked_touches_[i].valid)
+      continue;
+    if (tracked_touches_[i].end < touch_cutoff)
+      StopTrackingTouch(i);
+  }
+
+  for (const InProgressTouchEvdev& touch : touches) {
+    size_t slot = touch.slot;
+
+    bool arrived = touch.touching && !touch.was_touching;
+    bool departed = !touch.touching && touch.was_touching;
+    if (departed)
+      tracked_slots_[slot] = kNumTrackedTouches;
+    if (!touch.touching)
+      continue;
+
+    // Track all new touches until they move too far.
+    if (arrived)
+      TrackTouch(touch, time);
+
+    size_t t_ind = tracked_slots_[slot];
+    if (t_ind != kNumTrackedTouches) {
+      tracked_touches_[t_ind].end = time;
+      // Stop tracking if touch moves more than sqrt(kNoiseMaxMovement2).
+      if (Distance2(touch.x, touch.y, tracked_touches_[t_ind].x,
+                    tracked_touches_[t_ind].y) > kNoiseMaxMovement2) {
+        StopTrackingTouch(t_ind);
+      } else {
+        // Determine duration over which touches have been occuring in this
+        // position.
+        base::TimeDelta max_duration;
+        for (size_t i = tracked_touches_start_; i != tracked_touches_end_;
+             i = (i + 1) % kNumTrackedTouches) {
+          TrackedTouch* tracked_touch = &tracked_touches_[i];
+          if (!tracked_touch->valid)
+            continue;
+          if (Distance2(touch.x, touch.y, tracked_touch->x, tracked_touch->y) <=
+              kSamePositionMaxDistance2) {
+            base::TimeDelta duration = time - tracked_touch->begin;
+            if (duration > max_duration)
+              max_duration = duration;
+          }
+        }
+
+        if (max_duration.InMilliseconds() > kMinDurationMs) {
+          VLOG(2) << base::StringPrintf(
+              "Cancel tracking id %d, in position occurring for %ldms",
+              touch.tracking_id, max_duration.InMilliseconds());
+          slots_with_noise->set(slot);
+        }
+      }
+    }
+  }
+}
+
+void SinglePositionTouchNoiseFilter::StopTrackingTouch(size_t index) {
+  size_t slot = tracked_touches_[index].slot;
+  if (tracked_slots_[slot] == index)
+    tracked_slots_[slot] = kNumTrackedTouches;
+  tracked_touches_[index].valid = false;
+
+  // If first touch is canceled, remove all dead touches.
+  if (index == tracked_touches_start_) {
+    while (!tracked_touches_[tracked_touches_start_].valid &&
+           tracked_touches_start_ != tracked_touches_end_) {
+      tracked_touches_start_ =
+          (tracked_touches_start_ + 1) % kNumTrackedTouches;
+    }
+  }
+}
+
+void SinglePositionTouchNoiseFilter::TrackTouch(
+    const InProgressTouchEvdev& touch,
+    base::TimeDelta time) {
+  size_t index = (tracked_touches_end_ + 1) % kNumTrackedTouches;
+  // If we would reach the start touch index, we cannot track any more touches.
+  if (index == tracked_touches_start_)
+    return;
+
+  tracked_touches_end_ = index;
+  tracked_touches_[index].valid = true;
+  tracked_touches_[index].slot = touch.slot;
+  tracked_touches_[index].x = touch.x;
+  tracked_touches_[index].y = touch.y;
+  tracked_touches_[index].begin = time;
+  tracked_touches_[index].end = time;
+  tracked_slots_[touch.slot] = index;
+}
+
+SinglePositionTouchNoiseFilter::SinglePositionTouchNoiseFilter::TrackedTouch::
+    TrackedTouch()
+    : valid(false), slot(0), x(0), y(0) {
+}
+
+SinglePositionTouchNoiseFilter::SinglePositionTouchNoiseFilter::TrackedTouch::
+    ~TrackedTouch() {
+}
+
+}  // namespace ui