Add id properties to PointerEvent

ui/events/event.h

 // Copyright (c) 2012 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_EVENT_H_
 #define UI_EVENTS_EVENT_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 390 matching lines @@
 
   // |location_| multiplied by an optional transformation matrix for
   // rotations, animations and skews.
   gfx::PointF root_location_;
 };
 
 // Structure for handling common fields between touch and mouse to support
 // PointerEvents API.
 struct EVENTS_EXPORT PointerDetails {
  public:
-  PointerDetails() {}
-  explicit PointerDetails(EventPointerType pointer_type)
-      : pointer_type(pointer_type),
-        force(std::numeric_limits<float>::quiet_NaN()) {}
+  PointerDetails();
+  explicit PointerDetails(EventPointerType pointer_type);
   PointerDetails(EventPointerType pointer_type,
                  float radius_x,
                  float radius_y,
                  float force,
                  float tilt_x,
                  float tilt_y,
                  float tangential_pressure = 0.0f,
-                 int twist = 0)
-      : pointer_type(pointer_type),
-        // If we aren't provided with a radius on one axis, use the
-        // information from the other axis.
-        radius_x(radius_x > 0 ? radius_x : radius_y),
-        radius_y(radius_y > 0 ? radius_y : radius_x),
-        force(force),
-        tilt_x(tilt_x),
-        tilt_y(tilt_y),
-        tangential_pressure(tangential_pressure),
-        twist(twist) {}
-  PointerDetails(EventPointerType pointer_type, const gfx::Vector2d& offset)
-      : pointer_type(pointer_type),
-        force(std::numeric_limits<float>::quiet_NaN()),
-        offset(offset) {}
+                 int twist = 0,
+                 uint32_t id = 0);
+  PointerDetails(EventPointerType pointer_type, const gfx::Vector2d& offset);
+  PointerDetails(const PointerDetails& other);
 
   bool operator==(const PointerDetails& other) const {
     return pointer_type == other.pointer_type && radius_x == other.radius_x &&
            radius_y == other.radius_y &&
            (force == other.force ||
             (std::isnan(force) && std::isnan(other.force))) &&
            tilt_x == other.tilt_x && tilt_y == other.tilt_y &&
            tangential_pressure == other.tangential_pressure &&
-           twist == other.twist && offset == other.offset;
+           twist == other.twist && id == other.id && offset == other.offset;
   }
 
   // The type of pointer device.
   EventPointerType pointer_type = EventPointerType::POINTER_TYPE_UNKNOWN;
 
   // Radius of the X (major) axis of the touch ellipse. 0.0 if unknown.
   float radius_x = 0.0;
 
   // Radius of the Y (minor) axis of the touch ellipse. 0.0 if unknown.
   float radius_y = 0.0;
@@ skipping 11 matching lines @@
   // The normalized tangential pressure (or barrel pressure), typically set by
   // an additional control of the stylus, which has a range of [-1,1], where 0
   // is the neutral position of the control. Always 0 if the device does not
   // support it.
   float tangential_pressure = 0.0;
 
   // The clockwise rotation of a pen stylus around its own major axis, in
   // degrees in the range [0,359]. Always 0 if the device does not support it.
   int twist = 0;
 
+  // An identifier that uniquely identifies a pointer during its lifetime.
+  uint32_t id = 0;

[mustaq, 2017/01/31 00:24:13]

Where do we set the id from lower level events? Do you think we need to fix
events_win.cc::GetMousePointerDetailsFromNative()? We seem to have a TODO there.

+

[sadrul, 2017/01/31 17:05:13]

ui::TouchEvent has a touch_id(), and a unique_event_id(). It also has a
PointerDetails, which now also has a id(). How are they related? Can we remove
one of the ids from TouchEvent?

ditto for ui::PointerEvent.

[lanwei, 2017/02/01 02:58:12]

This id in PointerDetails makes more senses for stylus type, because we will get
an ID from lower level events from the OS. For touch event, this id will be just
0, and eventually in Blink, the pointer id will be set by the touch_id() from
ui::TouchEvent. I guess we can use get rid of touch_id(), if we will use this
id. Dave, Mustaq, what do you think?

[sadrul, 2017/02/01 20:59:39]

Replacing TouchEvent::touch_id() (and I guess PointerEvent::pointer_id() too)
with this new *Event::PointerDetails::id() sounds reasonable to me.

   // Only used by mouse wheel events. The amount to scroll. This is in multiples
   // of kWheelDelta.
   // Note: offset_.x() > 0/offset_.y() > 0 means scroll left/up.
   gfx::Vector2d offset;
 };
 
 class EVENTS_EXPORT MouseEvent : public LocatedEvent {
  public:
   explicit MouseEvent(const base::NativeEvent& native_event);
 
@@ skipping 566 matching lines @@
   // dispatched. This field gets a non-zero value only for gestures that are
   // released through TouchDispositionGestureFilter::SendGesture. The gesture
   // events that aren't fired directly in response to processing a touch-event
   // (e.g. timer fired ones), this id is zero. See crbug.com/618738.
   uint32_t unique_touch_event_id_;
 };
 
 }  // namespace ui
 
 #endif  // UI_EVENTS_EVENT_H_