MouseWheelEventManager is added to handle wheel events.

third_party/WebKit/Source/core/input/MouseWheelEventManager.cpp

+// Copyright 2017 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 "core/input/MouseWheelEventManager.h"
+
+#include "core/dom/Document.h"
+#include "core/events/WheelEvent.h"
+#include "core/frame/LocalFrameView.h"
+#include "core/input/EventHandler.h"
+#include "core/input/EventHandlingUtil.h"
+#include "core/input/ScrollManager.h"
+#include "core/layout/HitTestRequest.h"
+#include "core/layout/HitTestResult.h"
+#include "core/layout/api/LayoutViewItem.h"
+#include "public/platform/WebMouseWheelEvent.h"
+
+namespace blink {
+MouseWheelEventManager::MouseWheelEventManager(LocalFrame& frame,
+                                               ScrollManager& scroll_manager)
+    : frame_(frame), scroll_manager_(scroll_manager) {}
+
+DEFINE_TRACE(MouseWheelEventManager) {
+  visitor->Trace(frame_);
+  visitor->Trace(scroll_manager_);
+}
+
+WebInputEventResult MouseWheelEventManager::HandleWheelEvent(
+    const WebMouseWheelEvent& event) {
+#if OS(MACOSX)
+  // Filter Mac OS specific phases, usually with a zero-delta.
+  // https://crbug.com/553732
+  // TODO(chongz): EventSender sends events with
+  // |WebMouseWheelEvent::PhaseNone|,
+  // but it shouldn't.
+  const int kWheelEventPhaseNoEventMask = WebMouseWheelEvent::kPhaseEnded |
+                                          WebMouseWheelEvent::kPhaseCancelled |
+                                          WebMouseWheelEvent::kPhaseMayBegin;
+  if ((event.phase & kWheelEventPhaseNoEventMask) ||
+      (event.momentum_phase & kWheelEventPhaseNoEventMask))
+    return WebInputEventResult::kNotHandled;
+#endif
+  Document* doc = frame_->GetDocument();
+
+  if (doc->GetLayoutViewItem().IsNull())
+    return WebInputEventResult::kNotHandled;
+
+  LocalFrameView* view = frame_->View();
+  if (!view)
+    return WebInputEventResult::kNotHandled;
+
+  LayoutPoint v_point =
+      view->RootFrameToContents(FlooredIntPoint(event.PositionInRootFrame()));
+
+  HitTestRequest request(HitTestRequest::kReadOnly);
+  HitTestResult result(request, v_point);
+  doc->GetLayoutViewItem().HitTest(result);
+
+  Node* node = result.InnerNode();
+  // Wheel events should not dispatch to text nodes.
+  if (node && node->IsTextNode())
+    node = FlatTreeTraversal::Parent(*node);
+
+  // If we're over the frame scrollbar, scroll the document.
+  if (!node && result.GetScrollbar())
+    node = doc->documentElement();
+
+  LocalFrame* subframe = EventHandlingUtil::SubframeForTargetNode(node);
+  if (subframe) {
+    WebInputEventResult result =
+        subframe->GetEventHandler().HandleWheelEvent(event);
+    if (result != WebInputEventResult::kNotHandled)
+      scroll_manager_->SetFrameWasScrolledByUser();
+    return result;
+  }
+
+  if (node) {
+    WheelEvent* dom_event =
+        WheelEvent::Create(event, node->GetDocument().domWindow());
+    DispatchEventResult dom_event_result = node->DispatchEvent(dom_event);
+    if (dom_event_result != DispatchEventResult::kNotCanceled)
+      return EventHandlingUtil::ToWebInputEventResult(dom_event_result);
+  }
+
+  return WebInputEventResult::kNotHandled;
+}
+
+}  // namespace blink