Mac: Add rails for scrolling.

content/renderer/input/input_handler_proxy.cc

 // Copyright 2013 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/renderer/input/input_handler_proxy.h"
 
 #include "base/auto_reset.h"
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
@@ skipping 314 matching lines @@
   }
 
   return DID_NOT_HANDLE;
 }
 
 InputHandlerProxy::EventDisposition InputHandlerProxy::HandleMouseWheel(
     const WebMouseWheelEvent& wheel_event) {
   InputHandlerProxy::EventDisposition result = DID_NOT_HANDLE;
   cc::InputHandlerScrollResult scroll_result;
 
+  // TODO(ccameron): The rail information should be pushed down into
+  // InputHandler.
+  gfx::Vector2dF scroll_delta(

[jdduke (slow), 2015/03/19 22:27:44]

Not sure if it would be easier to read like:

gfx::Vector2dF scroll_delta(-wheel_event.deltaX, -wheel_event.deltaY);
if (wheel_event.railsMode == WebInputEvent::RailsModeVertical)
  scroll_delta.set_x(0);
if (wheel_event.railsMode == WebInputEvent::RailsModeHorizontal)
  scroll_delta.set_y(0);

+      wheel_event.railsMode != WebInputEvent::RailsModeVertical
+          ? -wheel_event.deltaX
+          : 0,
+      wheel_event.railsMode != WebInputEvent::RailsModeHorizontal
+          ? -wheel_event.deltaY
+          : 0);
+
   if (wheel_event.scrollByPage) {
     // TODO(jamesr): We don't properly handle scroll by page in the compositor
     // thread, so punt it to the main thread. http://crbug.com/236639
     result = DID_NOT_HANDLE;
   } else if (!wheel_event.canScroll) {
     // Wheel events with |canScroll| == false will not trigger scrolling,
     // only event handlers.  Forward to the main thread.
     result = DID_NOT_HANDLE;
   } else if (smooth_scroll_enabled_) {
     cc::InputHandler::ScrollStatus scroll_status =
-        input_handler_->ScrollAnimated(
-            gfx::Point(wheel_event.x, wheel_event.y),
-            gfx::Vector2dF(-wheel_event.deltaX, -wheel_event.deltaY));
+        input_handler_->ScrollAnimated(gfx::Point(wheel_event.x, wheel_event.y),
+                                       scroll_delta);
     switch (scroll_status) {
       case cc::InputHandler::SCROLL_STARTED:
         result = DID_HANDLE;
         break;
       case cc::InputHandler::SCROLL_IGNORED:
         result = DROP_EVENT;
       default:
         result = DID_NOT_HANDLE;
         break;
     }
   } else {
     cc::InputHandler::ScrollStatus scroll_status = input_handler_->ScrollBegin(
         gfx::Point(wheel_event.x, wheel_event.y), cc::InputHandler::WHEEL);
     switch (scroll_status) {
       case cc::InputHandler::SCROLL_STARTED: {
-        TRACE_EVENT_INSTANT2(
-            "input", "InputHandlerProxy::handle_input wheel scroll",
-            TRACE_EVENT_SCOPE_THREAD, "deltaX", -wheel_event.deltaX, "deltaY",
-            -wheel_event.deltaY);
+        TRACE_EVENT_INSTANT2("input",
+                             "InputHandlerProxy::handle_input wheel scroll",
+                             TRACE_EVENT_SCOPE_THREAD, "deltaX",
+                             scroll_delta.x(), "deltaY", scroll_delta.y());
         gfx::Point scroll_point(wheel_event.x, wheel_event.y);
-        gfx::Vector2dF scroll_delta(-wheel_event.deltaX, -wheel_event.deltaY);
         scroll_result = input_handler_->ScrollBy(scroll_point, scroll_delta);
         HandleOverscroll(scroll_point, scroll_result);
         input_handler_->ScrollEnd();
         result = scroll_result.did_scroll ? DID_HANDLE : DROP_EVENT;
         break;
       }
       case cc::InputHandler::SCROLL_IGNORED:
         // TODO(jamesr): This should be DROP_EVENT, but in cases where we fail
         // to properly sync scrollability it's safer to send the event to the
         // main thread. Change back to DROP_EVENT once we have synchronization
@@ skipping 562 matching lines @@
   // trigger a scroll, e.g., with a trivial time delta between fling updates.
   // Return true in this case to prevent early fling termination.
   if (std::abs(clipped_increment.width) < kScrollEpsilon &&
       std::abs(clipped_increment.height) < kScrollEpsilon)
     return true;
 
   return did_scroll;
 }
 
 }  // namespace content