Adding momentum/overscroll to views:: ScrollViews

ui/events/cocoa/events_mac.mm

Index: ui/events/cocoa/events_mac.mm
diff --git a/ui/events/cocoa/events_mac.mm b/ui/events/cocoa/events_mac.mm
index dbfd64c7fdcd36360671423bdd98fca793366f23..1ba0544915609de04a90598786b49f13c6858c0c 100644
--- a/ui/events/cocoa/events_mac.mm
+++ b/ui/events/cocoa/events_mac.mm
@@ -43,7 +43,7 @@ EventType EventTypeFromNative(const base::NativeEvent& native_event) {
     case NSMouseMoved:
       return ET_MOUSE_MOVED;
     case NSScrollWheel:
-      return ET_MOUSEWHEEL;
+      return ET_SCROLL;
     case NSMouseEntered:
       return ET_MOUSE_ENTERED;
     case NSMouseExited:
@@ -153,10 +153,10 @@ gfx::Vector2d GetMouseWheelOffset(const base::NativeEvent& event) {
     // 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.
+    const double kScrollbarPixelsPerCocoaTick = 40.0;
+    return gfx::Vector2d(kScrollbarPixelsPerCocoaTick * [event deltaX],
+                         kScrollbarPixelsPerCocoaTick * [event deltaY]);
   }
 }
 
@@ -198,9 +198,36 @@ bool GetScrollOffsets(const base::NativeEvent& native_event,
                       float* y_offset,
                       float* x_offset_ordinal,
                       float* y_offset_ordinal,
-                      int* finger_count) {
-  NOTIMPLEMENTED();
-  return false;
+                      int* finger_count,
+                      int* momentum_phase) {
+  gfx::Vector2d offset = GetMouseWheelOffset(native_event);
+  *x_offset_ordinal = offset.x();
+  *y_offset_ordinal = offset.y();
+
+  // For non-scrolling events, the finger count can be determined with
+  // [[native_event touchesMatchingPhase:NSTouchPhaseTouching inView:nil] count]
+  // but it's illegal to ask that of scroll events, so say two fingers.
+  *finger_count = 2;
+
+  // If a user just rests two fingers on the touchpad without moving, AppKit
+  // uses NSEventPhaseMayBegin. Treat this the same as NSEventPhaseBegan.
+  const NSUInteger kBeginPhaseMask = NSEventPhaseBegan | NSEventPhaseMayBegin;
+  const NSUInteger kEndPhaseMask = NSEventPhaseCancelled | NSEventPhaseEnded;
+
+  if ([native_event phase] & kBeginPhaseMask)
+    *momentum_phase |= EM_PHASE_MAY_BEGIN;
+
+  if (([native_event phase] | [native_event momentumPhase]) & kEndPhaseMask)
+    *momentum_phase |= EM_PHASE_END;
+  else if ([native_event momentumPhase] != NSEventPhaseNone)
+    *momentum_phase |= EM_PHASE_INERTIAL_UPDATE;
+
+  // If the event completely lacks phase information, there won't be further
+  // updates, so they must be treated as an end.
+  if (([native_event phase] | [native_event momentumPhase]) == NSEventPhaseNone)
+    *momentum_phase |= EM_PHASE_END;
+
+  return true;
 }
 
 bool GetFlingData(const base::NativeEvent& native_event,