Mac: Share kScrollbarPixelsPerCocoaTick between ui:: and blink:: events

ui/events/cocoa/events_mac.mm

 // 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.
 
 #include "ui/events/event_utils.h"
 
 #include <Cocoa/Cocoa.h>
 #include <stdint.h>
 
 #include "base/logging.h"
@@ skipping 122 matching lines @@
   }
   return 0;
 }
 
 PointerDetails GetMousePointerDetailsFromNative(
     const base::NativeEvent& native_event) {
   return PointerDetails(EventPointerType::POINTER_TYPE_MOUSE);
 }
 
 gfx::Vector2d GetMouseWheelOffset(const base::NativeEvent& event) {
-  if ([event respondsToSelector:@selector(hasPreciseScrollingDeltas)] &&
-      [event hasPreciseScrollingDeltas]) {

[Avi (use Gerrit), 2016/08/10 15:17:29]

Yay 10.7!

+  if ([event hasPreciseScrollingDeltas]) {
     // Handle continuous scrolling devices such as a Magic Mouse or a trackpad.
     // -scrollingDelta{X|Y} have float return types but they return values that
     // are already rounded to integers.
     // The values are the same as the values returned from calling
     // CGEventGetIntegerValueField(kCGScrollWheelEventPointDeltaAxis{1|2}).
     return gfx::Vector2d([event scrollingDeltaX], [event scrollingDeltaY]);
   } else {
     // Empirically, a value of 0.1 is typical for one mousewheel click. Positive
     // values when scrolling up or to the left. Scrolling quickly results in a
     // higher delta per click, up to about 15.0. (Quartz documentation suggests
     // +/-10).
-    // Multiply by 1000 to vaguely approximate WHEEL_DELTA on Windows (120).
-    const CGFloat kWheelDeltaMultiplier = 1000;
-    return gfx::Vector2d(kWheelDeltaMultiplier * [event deltaX],
-                         kWheelDeltaMultiplier * [event deltaY]);
+    // Use the same multiplier as content::WebMouseWheelEventBuilder. Note this
+    // differs from the value returned by CGEventSourceGetPixelsPerLine(), which
+    // is typically 10.
+    return gfx::Vector2d(kScrollbarPixelsPerCocoaTick * [event deltaX],
+                         kScrollbarPixelsPerCocoaTick * [event deltaY]);
   }
 }
 
 base::NativeEvent CopyNativeEvent(const base::NativeEvent& event) {
   return [event copy];
 }
 
 void ReleaseCopiedNativeEvent(const base::NativeEvent& event) {
   [event release];
 }
@@ skipping 91 matching lines @@
   uint16_t return_value;
   [text getCharacters:&return_value];
   return return_value;
 }
 
 bool IsCharFromNative(const base::NativeEvent& native_event) {
   return false;
 }
 
 }  // namespace ui