Port Chromium OS touch noise filtering to Chromium

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

Index: ui/events/ozone/evdev/touch_noise/horizontally_aligned_touch_noise_filter.cc
diff --git a/ui/events/ozone/evdev/touch_noise/horizontally_aligned_touch_noise_filter.cc b/ui/events/ozone/evdev/touch_noise/horizontally_aligned_touch_noise_filter.cc
new file mode 100644
index 0000000000000000000000000000000000000000..0c0e7bad7065610e72043c406440f4585da2a9ed
--- /dev/null
+++ b/ui/events/ozone/evdev/touch_noise/horizontally_aligned_touch_noise_filter.cc
@@ -0,0 +1,49 @@
+// 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/horizontally_aligned_touch_noise_filter.h"
+
+#include <cmath>
+
+#include "base/logging.h"
+#include "base/strings/stringprintf.h"
+#include "ui/gfx/geometry/point_f.h"
+
+namespace ui {
+
+namespace {
+
+// The maximum horizontal distance between touches considered aligned.
+int kMaxDistance = 3;
+
+}  // namespace
+
+void HorizontallyAlignedTouchNoiseFilter::FilterFrame(Frame* previous,
+                                                      Frame* current) {
+  for (size_t slot = 0; slot < kNumSlots; ++slot) {
+    Finger* cur = &current->fingers[slot];
+    Finger* prev = &previous->fingers[slot];
+
+    bool arrived = prev->tracking_id == -1 && cur->tracking_id >= 0;
+    if (!arrived)
+      continue;
+
+    // Check if within kMaxDistance of an existing touch.
+    for (size_t i = 0; i < kNumSlots; ++i) {
+      if (i == slot || current->fingers[i].tracking_id == -1)
+        continue;
+      if (std::abs(current->fingers[i].location.x() - cur->location.x()) <=
+          kMaxDistance) {
+        VLOG(2) << base::StringPrintf(
+            "Cancel tracking id %d, down at %ld at %s near touch %d at %s",
+            cur->tracking_id, current->timestamp.ToInternalValue(),
+            cur->location.ToString().c_str(), current->fingers[i].tracking_id,
+            current->fingers[i].location.ToString().c_str());
+        cur->canceled = true;
+      }
+    }
+  }
+}
+
+}  // namespace ui