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// 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_filter/far_apart_taps_touch_noise_filter.h"
#include <stddef.h>
#include <cmath>
#include "base/logging.h"
#include "base/metrics/histogram_macros.h"
#include "base/stl_util.h"
#include "base/strings/stringprintf.h"
namespace ui {
namespace {
// Minimum squared distance between taps to be considered far apart.
const int kMinDistance2 = 1500 * 1500;
// The minimum squared distance between taps to log to UMA.
const int kUmaMinDistance2 = 1000 * 1000;
// The maximum squared distance between taps to log to UMA.
const int kUmaMaxDistance2 = 3000 * 3000;
// Max time between taps considered.
const int kMaxTapDeltaMs = 30;
// Maximum squared movement of a touch to still be considered a tap.
const int kMaxTapMovement2 = 20 * 20;
// 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
void FarApartTapsTouchNoiseFilter::Filter(
const std::vector<InProgressTouchEvdev>& touches,
base::TimeTicks time,
std::bitset<kNumTouchEvdevSlots>* slots_with_noise) {
// Remove old taps.
base::TimeTicks tap_cutoff =
time - base::TimeDelta::FromMilliseconds(kMaxTapDeltaMs);
for (size_t i = 0; i < base::size(tracked_taps_); ++i) {
if (tracked_taps_[i].start < tap_cutoff)
tracked_taps_[i].Invalidate();
}
for (const InProgressTouchEvdev& touch : touches) {
// Only look at slots with active touches.
if (!touch.touching && !touch.was_touching)
continue;
size_t slot = touch.slot;
if (!touch.was_touching) {
// Track new finger info.
tracked_taps_[slot] = Tap(time, touch.x, touch.y);
} else if (tracked_taps_[slot].is_valid()) {
// Check if this finger has moved too far to be considered a tap.
if (kMaxTapMovement2 < Distance2(touch.x, touch.y, tracked_taps_[slot].x,
tracked_taps_[slot].y)) {
tracked_taps_[slot].Invalidate();
}
}
if (tracked_taps_[slot].is_valid()) {
// Check distance from other tracked taps.
int min_distance2 = -1;
for (size_t i = 0; i < base::size(tracked_taps_); ++i) {
if (i == slot || !tracked_taps_[i].is_valid())
continue;
int dist2 =
Distance2(tracked_taps_[i].x, tracked_taps_[i].y, touch.x, touch.y);
if (min_distance2 < 0 || dist2 < min_distance2)
min_distance2 = dist2;
}
// Log |min_distance2| to a UMA histogram to allow tuning of
// |kMinDistance2|.
if (min_distance2 > kUmaMinDistance2) {
UMA_HISTOGRAM_CUSTOM_COUNTS(
"Ozone.TouchNoiseFilter.FarApartTapDistance", min_distance2,
kUmaMinDistance2, kUmaMaxDistance2, 50);
}
if (min_distance2 > kMinDistance2) {
// The other finger should see this one on its next frame and also
// get canceled.
VLOG(2) << base::StringPrintf(
"Cancel tracking id %d %.0fpx from other current taps.",
touch.tracking_id, sqrt(min_distance2));
slots_with_noise->set(slot);
}
}
if (!touch.touching)
tracked_taps_[slot].Invalidate();
}
}
} // namespace ui