Fix mouse wheel over-scrolls when display is scaled and scroll is paginated

ui/events/blink/blink_event_util.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.
 
 // MSVC++ requires this to be set before any other includes to get M_PI.
 #define _USE_MATH_DEFINES
 
 #include "ui/events/blink/blink_event_util.h"
 
 #include <stddef.h>
@@ skipping 732 matching lines @@
   if (scale == 1.f && delta.IsZero())
     return scaled_event;
   if (event.type() == blink::WebMouseEvent::MouseWheel) {
     blink::WebMouseWheelEvent* wheel_event = new blink::WebMouseWheelEvent;
     scaled_event.reset(wheel_event);
     *wheel_event = static_cast<const blink::WebMouseWheelEvent&>(event);
     wheel_event->x += delta.x();
     wheel_event->y += delta.y();
     wheel_event->x *= scale;
     wheel_event->y *= scale;
-    wheel_event->deltaX *= scale;
-    wheel_event->deltaY *= scale;
+    if (!wheel_event->scrollByPage) {
+      wheel_event->deltaX *= scale;
+      wheel_event->deltaY *= scale;
+    }
     wheel_event->wheelTicksX *= scale;

[aelias_OOO_until_Jul13, 2017/02/16 22:11:13]

I think wheel tick count should be within the if block as well.

[chengx, 2017/02/17 08:26:02]

Done.

     wheel_event->wheelTicksY *= scale;
   } else if (blink::WebInputEvent::isMouseEventType(event.type())) {
     blink::WebMouseEvent* mouse_event = new blink::WebMouseEvent;
     scaled_event.reset(mouse_event);
     *mouse_event = static_cast<const blink::WebMouseEvent&>(event);
     mouse_event->x += delta.x();
     mouse_event->y += delta.y();
     mouse_event->x *= scale;
     mouse_event->y *= scale;
     mouse_event->windowX = mouse_event->x;
@@ skipping 15 matching lines @@
   } else if (blink::WebInputEvent::isGestureEventType(event.type())) {
     blink::WebGestureEvent* gesture_event = new blink::WebGestureEvent;
     scaled_event.reset(gesture_event);
     *gesture_event = static_cast<const blink::WebGestureEvent&>(event);
     gesture_event->x += delta.x();
     gesture_event->y += delta.y();
     gesture_event->x *= scale;
     gesture_event->y *= scale;
     switch (gesture_event->type()) {
       case blink::WebInputEvent::GestureScrollUpdate:
-        gesture_event->data.scrollUpdate.deltaX *= scale;
-        gesture_event->data.scrollUpdate.deltaY *= scale;
+        if (gesture_event->data.scrollUpdate.deltaUnits !=
+            blink::WebGestureEvent::ScrollUnits::Page) {
+          gesture_event->data.scrollUpdate.deltaX *= scale;
+          gesture_event->data.scrollUpdate.deltaY *= scale;
+        }
         break;
       case blink::WebInputEvent::GestureScrollBegin:
-        gesture_event->data.scrollBegin.deltaXHint *= scale;
-        gesture_event->data.scrollBegin.deltaYHint *= scale;
+        if (gesture_event->data.scrollBegin.deltaHintUnits !=
+            blink::WebGestureEvent::ScrollUnits::Page) {
+          gesture_event->data.scrollBegin.deltaXHint *= scale;
+          gesture_event->data.scrollBegin.deltaYHint *= scale;
+        }
         break;
 
       case blink::WebInputEvent::GesturePinchUpdate:
         // Scale in pinch gesture is DSF agnostic.
         break;
 
       case blink::WebInputEvent::GestureDoubleTap:
       case blink::WebInputEvent::GestureTap:
       case blink::WebInputEvent::GestureTapUnconfirmed:
         gesture_event->data.tap.width *= scale;
@@ skipping 157 matching lines @@
   switch (type) {
     case blink::WebGestureEvent::GestureScrollUpdate:
     case blink::WebGestureEvent::GesturePinchUpdate:
       return true;
     default:
       return false;
   }
 }
 
 }  // namespace ui