MacViews: Support continuous scrolling and horizontal scrolling

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>
 
+#import "base/mac/mac_util.h"
+#import "base/mac/sdk_forward_declarations.h"
 #include "base/logging.h"
 #include "base/time/time.h"
 #include "build/build_config.h"
 #include "ui/events/cocoa/cocoa_event_utils.h"
 #include "ui/events/event_utils.h"
 #import "ui/events/keycodes/keyboard_code_conversion_mac.h"
 #include "ui/gfx/point.h"
 #include "ui/gfx/vector2d.h"
 
 namespace ui {
@@ skipping 104 matching lines @@
       return EF_RIGHT_MOUSE_BUTTON;
     case NSOtherMouseDown:
     case NSOtherMouseUp:
     case NSOtherMouseDragged:
       return EF_MIDDLE_MOUSE_BUTTON;
   }
   return 0;
 }
 
 gfx::Vector2d GetMouseWheelOffset(const base::NativeEvent& event) {
-  // 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]);
+  if (base::mac::IsOSLionOrLater() && [event hasPreciseScrollingDeltas]) {
+      return gfx::Vector2d([event scrollingDeltaX], [event scrollingDeltaY]);

[Andre, 2014/08/29 23:31:34]

Scrolling feels pretty good on Magic Mouse without any multiplier.

[tapted, 2014/09/02 09:10:25]

nit: It might be worth documenting what the numbers are like. The function
returns integers so some things might be interested in the extra precision.

[Andre, 2014/09/02 17:05:05]

Done.

+  } 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]);
+  }
 }
 
 base::NativeEvent CopyNativeEvent(const base::NativeEvent& event) {
   return [event copy];
 }
 
 void ReleaseCopiedNativeEvent(const base::NativeEvent& event) {
   [event release];
 }
 
@@ skipping 102 matching lines @@
   uint16 return_value;
   [text getCharacters:&return_value];
   return return_value;
 }
 
 bool IsCharFromNative(const base::NativeEvent& native_event) {
   return false;
 }
 
 }  // namespace ui