Coalesced mouse wheel event has the position of the most recent event.

content/common/input/event_with_latency_info_unittest.cc

 // 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.
 
 #include "content/common/input/event_with_latency_info.h"
 
 #include <limits>
 
 #include "testing/gtest/include/gtest/gtest.h"
 #include "third_party/WebKit/public/web/WebInputEvent.h"
@@ skipping 284 matching lines @@
   pinch1 = CreateGesture(WebInputEvent::GesturePinchUpdate, 1, 1);
   pinch1.event.data.pinchUpdate.scale = 10.0f;
   EXPECT_TRUE(CanCoalesce(pinch0, pinch1));
   Coalesce(pinch0, &pinch1);
   EXPECT_EQ(numeric_limits<float>::max(), pinch1.event.data.pinchUpdate.scale);
 }
 
 TEST_F(EventWithLatencyInfoTest, WebMouseWheelEventCoalescing) {
   MouseWheelEventWithLatencyInfo mouse_wheel_0 = CreateMouseWheel(1, 1);
   MouseWheelEventWithLatencyInfo mouse_wheel_1 = CreateMouseWheel(2, 2);
-
   // WebMouseWheelEvent objects with same values except different deltaX and
   // deltaY should coalesce.
   EXPECT_TRUE(CanCoalesce(mouse_wheel_0, mouse_wheel_1));
 
   // WebMouseWheelEvent objects with different modifiers should not coalesce.
   mouse_wheel_0 = CreateMouseWheel(1, 1);
   mouse_wheel_1 = CreateMouseWheel(1, 1);
   mouse_wheel_0.event.modifiers = WebInputEvent::ControlKey;
   mouse_wheel_1.event.modifiers = WebInputEvent::ShiftKey;
   EXPECT_FALSE(CanCoalesce(mouse_wheel_0, mouse_wheel_1));
+
+  // Coalesce old and new events.
+  mouse_wheel_0 = CreateMouseWheel(1, 1);
+  mouse_wheel_0.event.x = 1;
+  mouse_wheel_0.event.y = 1;
+  mouse_wheel_1 = CreateMouseWheel(2, 2);
+  mouse_wheel_1.event.x = 2;
+  mouse_wheel_1.event.y = 2;
+  MouseWheelEventWithLatencyInfo mouse_wheel_1_copy = mouse_wheel_1;
+  EXPECT_TRUE(CanCoalesce(mouse_wheel_0, mouse_wheel_1));
+  EXPECT_EQ(mouse_wheel_0.event.modifiers, mouse_wheel_1.event.modifiers);
+  EXPECT_EQ(mouse_wheel_0.event.scrollByPage, mouse_wheel_1.event.scrollByPage);
+  EXPECT_EQ(mouse_wheel_0.event.phase, mouse_wheel_1.event.phase);
+  EXPECT_EQ(mouse_wheel_0.event.momentumPhase,
+            mouse_wheel_1.event.momentumPhase);
+  EXPECT_EQ(mouse_wheel_0.event.hasPreciseScrollingDeltas,
+            mouse_wheel_1.event.hasPreciseScrollingDeltas);
+  Coalesce(mouse_wheel_0, &mouse_wheel_1);
+
+  // Coalesced event has the position of the most recent event.
+  EXPECT_EQ(1, mouse_wheel_1.event.x);
+  EXPECT_EQ(1, mouse_wheel_1.event.y);
+
+  // deltaX/Y, wheelTicksX/Y, and movementX/Y of the coalesced event are
+  // calculated properly.
+  EXPECT_EQ(mouse_wheel_1_copy.event.deltaX + mouse_wheel_0.event.deltaX,
+            mouse_wheel_1.event.deltaX);
+  EXPECT_EQ(mouse_wheel_1_copy.event.deltaY + mouse_wheel_0.event.deltaY,
+            mouse_wheel_1.event.deltaY);
+  EXPECT_EQ(
+      mouse_wheel_1_copy.event.wheelTicksX + mouse_wheel_0.event.wheelTicksX,
+      mouse_wheel_1.event.wheelTicksX);
+  EXPECT_EQ(
+      mouse_wheel_1_copy.event.wheelTicksY + mouse_wheel_0.event.wheelTicksY,
+      mouse_wheel_1.event.wheelTicksY);
+  EXPECT_EQ(mouse_wheel_1_copy.event.movementX + mouse_wheel_0.event.movementX,
+            mouse_wheel_1.event.movementX);
+  EXPECT_EQ(mouse_wheel_1_copy.event.movementY + mouse_wheel_0.event.movementY,
+            mouse_wheel_1.event.movementY);
 }
 
 // Coalescing preserves the newer timestamp.
 TEST_F(EventWithLatencyInfoTest, TimestampCoalescing) {
   MouseWheelEventWithLatencyInfo mouse_wheel_0 = CreateMouseWheel(1, 1);
   mouse_wheel_0.event.timeStampSeconds = 5.0;
   MouseWheelEventWithLatencyInfo mouse_wheel_1 = CreateMouseWheel(2, 2);
   mouse_wheel_1.event.timeStampSeconds = 10.0;
 
   EXPECT_TRUE(CanCoalesce(mouse_wheel_0, mouse_wheel_1));
   Coalesce(mouse_wheel_1, &mouse_wheel_0);
   EXPECT_EQ(10.0, mouse_wheel_0.event.timeStampSeconds);
 }
 
 }  // namespace
 }  // namespace content