ui::GestureProvider gives GestureEventData the number of touch points.

ui/events/gesture_detection/gesture_provider.cc

Index: ui/events/gesture_detection/gesture_provider.cc
diff --git a/ui/events/gesture_detection/gesture_provider.cc b/ui/events/gesture_detection/gesture_provider.cc
index 6c581febd91294374a308c53e6675d7bec098932..d675a4752677da84899c1554b21769f4abc7f819 100644
--- a/ui/events/gesture_detection/gesture_provider.cc
+++ b/ui/events/gesture_detection/gesture_provider.cc
@@ -35,16 +35,24 @@ GestureEventData CreateGesture(EventType type,
                                base::TimeTicks time,
                                float x,
                                float y,
+                               size_t touch_point_count,
                                const GestureEventDetails& details) {

[jdduke (slow), 2014/04/08 21:07:41]

Might as well pass this by value, then you can call |details.set_touch_points|
directly.

[tdresser, 2014/04/09 14:50:48]

I'm still passing by reference, based on the change I made to address your
comment below.

-  return GestureEventData(type, motion_event_id, time, x, y, details);
+  DCHECK_NE(0u, touch_point_count);
+  GestureEventDetails d = details;
+  d.set_touch_points(touch_point_count);
+  return GestureEventData(type, motion_event_id, time, x, y, d);
 }
 
 GestureEventData CreateGesture(EventType type,
                                int motion_event_id,
                                base::TimeTicks time,
                                float x,
-                               float y) {
-  return GestureEventData(type, motion_event_id, time, x, y);
+                               float y,
+                               size_t touch_point_count) {
+  DCHECK_NE(0u, touch_point_count);
+  GestureEventDetails details;
+  details.set_touch_points(touch_point_count);
+  return GestureEventData(type, motion_event_id, time, x, y, details);

[jdduke (slow), 2014/04/08 21:07:41]

Hmm, now that we only use one constructor for GestureEventData, I wonder if we
should just change its constructor to take a touch_point_count, and have it set
|set_touch_points()| inside the constructor?

Otherwise, please delete the constructor that doesn't take details.

[tdresser, 2014/04/09 14:50:48]

Is this what you were thinking?

 }
 
 GestureEventData CreateGesture(EventType type,
@@ -55,13 +63,18 @@ GestureEventData CreateGesture(EventType type,
                        event.GetEventTime(),
                        event.GetX(),
                        event.GetY(),
+                       event.GetPointerCount(),
                        details);
 }
 
 GestureEventData CreateGesture(EventType type,
                                const MotionEvent& event) {
-  return CreateGesture(
-      type, event.GetId(), event.GetEventTime(), event.GetX(), event.GetY());
+  return CreateGesture(type,
+                       event.GetId(),
+                       event.GetEventTime(),
+                       event.GetX(),
+                       event.GetY(),
+                       event.GetPointerCount());
 }
 
 GestureEventDetails CreateTapGestureDetails(EventType type,
@@ -123,8 +136,12 @@ class GestureProvider::ScaleGestureListenerImpl
                           const MotionEvent& e) OVERRIDE {
     if (!pinch_event_sent_)
       return;
-    provider_->Send(CreateGesture(
-        ET_GESTURE_PINCH_END, e.GetId(), detector.GetEventTime(), 0, 0));
+    provider_->Send(CreateGesture(ET_GESTURE_PINCH_END,
+                                  e.GetId(),
+                                  detector.GetEventTime(),
+                                  0,
+                                  0,
+                                  e.GetPointerCount()));
     pinch_event_sent_ = false;
   }
 
@@ -138,7 +155,8 @@ class GestureProvider::ScaleGestureListenerImpl
                                     e.GetId(),
                                     detector.GetEventTime(),
                                     detector.GetFocusX(),
-                                    detector.GetFocusY()));
+                                    detector.GetFocusY(),
+                                    e.GetPointerCount()));
     }
 
     float scale = detector.GetScaleFactor();
@@ -163,6 +181,7 @@ class GestureProvider::ScaleGestureListenerImpl
                                   detector.GetEventTime(),
                                   detector.GetFocusX(),
                                   detector.GetFocusY(),
+                                  e.GetPointerCount(),
                                   pinch_details));
     return true;
   }
@@ -274,6 +293,9 @@ class GestureProvider::GestureListenerImpl
                         const MotionEvent& e2,
                         float raw_distance_x,
                         float raw_distance_y) OVERRIDE {
+    DCHECK_NE(0u, e1.GetPointerCount());
+    DCHECK_NE(0u, e2.GetPointerCount());
+
     float distance_x = raw_distance_x;
     float distance_y = raw_distance_y;
     if (!seen_first_scroll_event_) {
@@ -305,12 +327,8 @@ class GestureProvider::GestureListenerImpl
       // scroll deltas are in the opposite direction.
       GestureEventDetails scroll_details(
           ET_GESTURE_SCROLL_BEGIN, -raw_distance_x, -raw_distance_y);
-      provider_->Send(CreateGesture(ET_GESTURE_SCROLL_BEGIN,
-                                    e2.GetId(),
-                                    e2.GetEventTime(),

[jdduke (slow), 2014/04/08 21:07:41]

This is a change in behavior.  GestureScrollBegin attaches to a layer based on
the provided coordinate, and I think we want that coordinate to remain the point
of the first touch.

[tdresser, 2014/04/09 14:50:48]

Done.

-                                    e1.GetX(),
-                                    e1.GetY(),
-                                    scroll_details));
+      provider_->Send(
+          CreateGesture(ET_GESTURE_SCROLL_BEGIN, e2, scroll_details));
     }
 
     // distance_x and distance_y is the scrolling offset since last OnScroll.
@@ -544,6 +562,9 @@ GestureProvider::~GestureProvider() {}
 bool GestureProvider::OnTouchEvent(const MotionEvent& event) {
   TRACE_EVENT1("input", "GestureProvider::OnTouchEvent",
                "action", GetMotionEventActionName(event.GetAction()));
+
+  DCHECK_NE(0u, event.GetPointerCount());
+
   if (!CanHandle(event))
     return false;
 
@@ -667,7 +688,8 @@ void GestureProvider::Send(const GestureEventData& gesture) {
                            gesture.motion_event_id,
                            gesture.time,
                            gesture.x,
-                           gesture.y));
+                           gesture.y,
+                           gesture.details.touch_points()));
       needs_tap_ending_event_ = false;
       break;
     case ET_GESTURE_DOUBLE_TAP:
@@ -702,7 +724,8 @@ void GestureProvider::Send(const GestureEventData& gesture) {
                            gesture.motion_event_id,
                            gesture.time,
                            gesture.x,
-                           gesture.y));
+                           gesture.y,
+                           gesture.details.touch_points()));
       pinch_in_progress_ = true;
       break;
     case ET_GESTURE_PINCH_END:
@@ -731,7 +754,8 @@ void GestureProvider::SendTapCancelIfNecessary(
                      gesture.motion_event_id,
                      gesture.time,
                      gesture.x,
-                     gesture.y));
+                     gesture.y,
+                     gesture.details.touch_points()));
 }
 
 bool GestureProvider::SendLongTapIfNecessary(const MotionEvent& event) {