Track whether a scroll sequence has been partially prevented

ui/events/gesture_event_details.h

 // Copyright 2014 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_GESTURE_DETECTION_GESTURE_EVENT_DETAILS_H_
 #define UI_EVENTS_GESTURE_DETECTION_GESTURE_EVENT_DETAILS_H_
 
 #include "base/logging.h"
 #include "ui/events/event_constants.h"
 #include "ui/events/events_base_export.h"
 #include "ui/gfx/rect.h"
 #include "ui/gfx/rect_conversions.h"
 
 namespace ui {
 
 struct EVENTS_BASE_EXPORT GestureEventDetails {
  public:
   GestureEventDetails();
   explicit GestureEventDetails(EventType type);
   GestureEventDetails(EventType type, float delta_x, float delta_y);
 
+  // The caller is responsible for ensuring that the gesture data from |other|
+  // is compatible and sufficient for that expected by gestures of |type|.
+  GestureEventDetails(EventType type, const GestureEventDetails& other);
+
   EventType type() const { return type_; }
 
   int touch_points() const { return touch_points_; }
   void set_touch_points(int touch_points) {
     DCHECK_GT(touch_points, 0);
     touch_points_ = touch_points;
   }
 
   int oldest_touch_id() const { return oldest_touch_id_; }
   void set_oldest_touch_id(int oldest_touch_id) {
     DCHECK_GE(oldest_touch_id, 0);
     oldest_touch_id_ = oldest_touch_id;
   }
 
   // TODO(tdresser): Return RectF. See crbug.com/337824.
   const gfx::Rect bounding_box() const {
     return ToEnclosingRect(bounding_box_);
   }
 
   const gfx::RectF& bounding_box_f() const {
     return bounding_box_;
   }
 
   void set_bounding_box(const gfx::RectF& box) { bounding_box_ = box; }
 
   float scroll_x_hint() const {
     DCHECK_EQ(ET_GESTURE_SCROLL_BEGIN, type_);
-    return data.scroll_begin.x_hint;
+    return data_.scroll_begin.x_hint;
   }
 
   float scroll_y_hint() const {
     DCHECK_EQ(ET_GESTURE_SCROLL_BEGIN, type_);
-    return data.scroll_begin.y_hint;
+    return data_.scroll_begin.y_hint;
   }
 
   float scroll_x() const {
     DCHECK_EQ(ET_GESTURE_SCROLL_UPDATE, type_);
-    return data.scroll_update.x;
+    return data_.scroll_update.x;
   }
 
   float scroll_y() const {
     DCHECK_EQ(ET_GESTURE_SCROLL_UPDATE, type_);
-    return data.scroll_update.y;
+    return data_.scroll_update.y;
   }
 
   float velocity_x() const {
     DCHECK_EQ(ET_SCROLL_FLING_START, type_);
-    return data.fling_velocity.x;
+    return data_.fling_velocity.x;
   }
 
   float velocity_y() const {
     DCHECK_EQ(ET_SCROLL_FLING_START, type_);
-    return data.fling_velocity.y;
+    return data_.fling_velocity.y;
   }
 
   float first_finger_width() const {
     DCHECK_EQ(ET_GESTURE_TWO_FINGER_TAP, type_);
-    return data.first_finger_enclosing_rectangle.width;
+    return data_.first_finger_enclosing_rectangle.width;
   }
 
   float first_finger_height() const {
     DCHECK_EQ(ET_GESTURE_TWO_FINGER_TAP, type_);
-    return data.first_finger_enclosing_rectangle.height;
+    return data_.first_finger_enclosing_rectangle.height;
   }
 
   float scale() const {
     DCHECK_EQ(ET_GESTURE_PINCH_UPDATE, type_);
-    return data.scale;
+    return data_.scale;
   }
 
   bool swipe_left() const {
     DCHECK_EQ(ET_GESTURE_SWIPE, type_);
-    return data.swipe.left;
+    return data_.swipe.left;
   }
 
   bool swipe_right() const {
     DCHECK_EQ(ET_GESTURE_SWIPE, type_);
-    return data.swipe.right;
+    return data_.swipe.right;
   }
 
   bool swipe_up() const {
     DCHECK_EQ(ET_GESTURE_SWIPE, type_);
-    return data.swipe.up;
+    return data_.swipe.up;
   }
 
   bool swipe_down() const {
     DCHECK_EQ(ET_GESTURE_SWIPE, type_);
-    return data.swipe.down;
+    return data_.swipe.down;
   }
 
   int tap_count() const {
     DCHECK(type_ == ET_GESTURE_TAP ||
            type_ == ET_GESTURE_TAP_UNCONFIRMED ||
            type_ == ET_GESTURE_DOUBLE_TAP);
-    return data.tap_count;
+    return data_.tap_count;
   }
 
   void set_tap_count(int tap_count) {
     DCHECK_GE(tap_count, 0);
     DCHECK(type_ == ET_GESTURE_TAP ||
            type_ == ET_GESTURE_TAP_UNCONFIRMED ||
            type_ == ET_GESTURE_DOUBLE_TAP);
-    data.tap_count = tap_count;
+    data_.tap_count = tap_count;
   }
 
   void set_scale(float scale) {
     DCHECK_GE(scale, 0.0f);
     DCHECK_EQ(type_, ET_GESTURE_PINCH_UPDATE);
-    data.scale = scale;
+    data_.scale = scale;
+  }
+
+  void mark_previous_scroll_update_in_sequence_prevented() {
+    DCHECK_EQ(ET_GESTURE_SCROLL_UPDATE, type_);
+    data_.scroll_update.previous_update_in_sequence_prevented = true;
+  }
+
+  bool previous_scroll_update_in_sequence_prevented() const {
+    DCHECK_EQ(ET_GESTURE_SCROLL_UPDATE, type_);
+    return data_.scroll_update.previous_update_in_sequence_prevented;
   }
 
  private:
   EventType type_;
   union Details {
     Details();
     struct {  // SCROLL start details.
       // Distance that caused the scroll to start.  Generally redundant with
       // the x/y values from the first scroll_update.
       float x_hint;
       float y_hint;
     } scroll_begin;
 
     struct {  // SCROLL delta.
       float x;
       float y;
+      // Whether any previous scroll update in the current scroll sequence was
+      // suppressed because the underlying touch was consumed.
+      bool previous_update_in_sequence_prevented;
     } scroll_update;
 
     float scale;  // PINCH scale.
 
     struct {  // FLING velocity.
       float x;
       float y;
     } fling_velocity;
 
     // Dimensions of the first finger's enclosing rectangle for
     // TWO_FINGER_TAP.
     struct {
       float width;
       float height;
     } first_finger_enclosing_rectangle;
 
     struct {  // SWIPE direction.
       bool left;
       bool right;
       bool up;
       bool down;
     } swipe;
 
     // Tap information must be set for ET_GESTURE_TAP,
     // ET_GESTURE_TAP_UNCONFIRMED, and ET_GESTURE_DOUBLE_TAP events.
     int tap_count;  // TAP repeat count.
-  } data;
+  } data_;
 
   int touch_points_;  // Number of active touch points in the gesture.
 
   // Bounding box is an axis-aligned rectangle that contains all the
   // enclosing rectangles of the touch-points in the gesture.
   gfx::RectF bounding_box_;
 
   // The touch id of the oldest touch contributing to the gesture.
   int oldest_touch_id_;
 };
 
 }  // namespace ui
 
 #endif  // UI_EVENTS_GESTURE_DETECTION_GESTURE_EVENT_DETAILS_H_