Expose native, desktop and mobile gesture detection defaults

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 "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/event_types.h"
@@ skipping 475 matching lines @@
   // If source / target windows are provided, the model location will be
   // converted from |source| coordinate system to |target| coordinate system.
   template <class T>
   TouchEvent(const TouchEvent& model, T* source, T* target)
       : LocatedEvent(model, source, target),
         touch_id_(model.touch_id_),
         unique_event_id_(model.unique_event_id_),
         radius_x_(model.radius_x_),
         radius_y_(model.radius_y_),
         rotation_angle_(model.rotation_angle_),
-        force_(model.force_) {}
+        force_(model.force_),
+        may_cause_scrolling_(model.may_cause_scrolling_) {}
 
   TouchEvent(EventType type,
              const gfx::PointF& location,
              int touch_id,
              base::TimeDelta time_stamp);
 
   TouchEvent(EventType type,
              const gfx::PointF& location,
              int flags,
              int touch_id,
              base::TimeDelta timestamp,
              float radius_x,
              float radius_y,
              float angle,
              float force);
 
   ~TouchEvent() override;
 
   // The id of the pointer this event modifies.
   int touch_id() const { return touch_id_; }
   // A unique identifier for this event.
   uint64 unique_event_id() const { return unique_event_id_; }
   float radius_x() const { return radius_x_; }
   float radius_y() const { return radius_y_; }
   float rotation_angle() const { return rotation_angle_; }
   float force() const { return force_; }
 
+  void set_may_cause_scrolling(bool causes) { may_cause_scrolling_ = causes; }

[jdduke (slow), 2014/12/11 19:06:38]

I'm open to different naming here, or event a different way of propagating this
bit.

+  bool may_cause_scrolling() const { return may_cause_scrolling_; }
+
   // Used for unit tests.
   void set_radius_x(const float r) { radius_x_ = r; }
   void set_radius_y(const float r) { radius_y_ = r; }
 
   // Overridden from LocatedEvent.
   void UpdateForRootTransform(
       const gfx::Transform& inverted_root_transform) override;
 
   // Marks the event as not participating in synchronous gesture recognition.
   void DisableSynchronousHandling();
@@ skipping 25 matching lines @@
   float radius_x_;
 
   // Radius of the Y (minor) axis of the touch ellipse. 0.0 if unknown.
   float radius_y_;
 
   // Angle of the major axis away from the X axis. Default 0.0.
   float rotation_angle_;
 
   // Force (pressure) of the touch. Normalized to be [0, 1]. Default to be 0.0.
   float force_;
+
+  // Whether the (unhandled) touch event will produce a scroll event (i.e., it's
+  // a touchmove and exceeds the platform slop region). Defaults to false.
+  bool may_cause_scrolling_;

[jdduke (slow), 2014/12/11 19:32:54]

Awfully tempting to make this mutable... Would avoid the need to restructure
event-related APIs, and emphasizes that the value is likely to change without
affecting the core event, but it might be somewhat confusing...

 };
 
 // An interface that individual platforms can use to store additional data on
 // KeyEvent.
 //
 // Currently only used in mojo.
 class EVENTS_EXPORT ExtendedKeyEventData {
  public:
   virtual ~ExtendedKeyEventData() {}
 
@@ skipping 243 matching lines @@
 
   const GestureEventDetails& details() const { return details_; }
 
  private:
   GestureEventDetails details_;
 };
 
 }  // namespace ui
 
 #endif  // UI_EVENTS_EVENT_H_