Port Chromium OS touch noise filtering to Chromium

ui/events/ozone/evdev/touch_evdev_types.h

+// 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.
+
+#ifndef UI_EVENTS_OZONE_EVDEV_TOUCH_EVDEV_TYPES_H_
+#define UI_EVENTS_OZONE_EVDEV_TOUCH_EVDEV_TYPES_H_
+
+#include "base/basictypes.h"
+#include "ui/events/event_constants.h"
+#include "ui/events/ozone/evdev/events_ozone_evdev_export.h"
+
+namespace ui {
+
+// Number of supported touch slots. ABS_MT_SLOT messages with
+// value >= kNumTouchEvdevSlots are ignored.
+const int kNumTouchEvdevSlots = 20;
+
+// Contains information about an in progress touch.
+struct EVENTS_OZONE_EVDEV_EXPORT InProgressTouchEvdev {
+  InProgressTouchEvdev();
+  ~InProgressTouchEvdev();
+
+  // Whether there is new information for the touch.
+  bool altered;
+
+  // Whether the touch was canceled. Touch events should be ignored till a press
+  // initiates a new touch.
+  bool cancelled;

[flackr, 2015/03/17 03:54:15]

I think this can be equivalent to type == ET_TOUCH_CANCELLED.

+
+  float x;
+  float y;
+  int tracking_id;
+  size_t slot;

[spang, 2015/03/18 19:20:12]

Is it needed to duplicate the offset into the slots vector here as a field?

[pkotwicz1, 2015/03/18 20:00:02]

Yes, it is a duplicate. It makes the interface of
TouchNoiseFinder::HandleTouches() much easier to document

+  EventType type;

[pkotwicz1, 2015/03/18 20:00:02]

It sounds like you are suggesting removing the |type| field from the struct. The
TouchNoiseFilters currently make use of the |type| field (e.g.
HorizontallyAlignedTouchNoiseFilter).

We can remove the |type| field if we add a |previous_tracking_id| field. This
would allow the TouchNoiseFilters to infer whether a touch is press or is a
move.
Alternatively, TouchNoiseFinder can keep track of the tracking ids for the
previous time that TouchNoiseFinder::HandleTouches() was called.

[spang, 2015/03/18 20:52:18]

Yes (or rather, breaking it into its constituent parts).
I proposed a new field "client_pressed" to track that.

Maybe it should be called "was_pressed" if it's also need for filtering, though.

+  float radius_x;
+  float radius_y;
+  float pressure;
+};
+
+}  // namespace ui
+
+#endif  // UI_EVENTS_OZONE_EVDEV_TOUCH_EVDEV_TYPES_H_