Adding phase info to wheel events migrated to wheel phase handler class.

content/browser/renderer_host/input/mouse_wheel_phase_handler.cc

+// 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 "content/browser/renderer_host/input/mouse_wheel_phase_handler.h"
+
+#include "content/browser/renderer_host/render_widget_host_impl.h"
+#include "content/browser/renderer_host/render_widget_host_input_event_router.h"
+#include "content/browser/renderer_host/render_widget_host_view_base.h"
+
+namespace content {
+MouseWheelPhaseHandler::MouseWheelPhaseHandler(
+    RenderWidgetHostImpl* const host,
+    RenderWidgetHostViewBase* const host_view)
+    : host_(RenderWidgetHostImpl::From(host)), host_view_(host_view) {}
+
+void MouseWheelPhaseHandler::AddPhaseIfNeededAndScheduleEndEvent(
+    blink::WebMouseWheelEvent& mouse_wheel_event,
+    bool should_route_event) {
+  bool has_phase =
+      mouse_wheel_event.phase != blink::WebMouseWheelEvent::kPhaseNone ||
+      mouse_wheel_event.momentum_phase != blink::WebMouseWheelEvent::kPhaseNone;
+  if (has_phase) {
+    if (mouse_wheel_event.phase == blink::WebMouseWheelEvent::kPhaseEnded) {
+      // Don't send the wheel end event immediately, start a timer instead to
+      // see whether momentum phase of the scrolling starts or not.
+      ScheduleMouseWheelEndDispatching(mouse_wheel_event, should_route_event);
+    } else if (mouse_wheel_event.phase ==
+               blink::WebMouseWheelEvent::kPhaseBegan) {
+      // A new scrolling sequence has started, send the pending wheel end
+      // event to end the previous scrolling sequence.
+      DispatchPendingWheelEndEvent();
+    } else if (mouse_wheel_event.momentum_phase ==
+               blink::WebMouseWheelEvent::kPhaseBegan) {
+      // Momentum phase has started, drop the pending wheel end event to make
+      // sure that no wheel end event will be sent during the momentum phase
+      // of scrolling.
+      IgnorePendingWheelEndEvent();
+    }
+  } else {  // !has_phase
+    if (!mouse_wheel_end_dispatch_timer_.IsRunning()) {
+      mouse_wheel_event.phase = blink::WebMouseWheelEvent::kPhaseBegan;
+      ScheduleMouseWheelEndDispatching(mouse_wheel_event, should_route_event);
+    } else {  // mouse_wheel_end_dispatch_timer_.IsRunning()
+      bool non_zero_delta =
+          mouse_wheel_event.delta_x || mouse_wheel_event.delta_y;
+      mouse_wheel_event.phase =
+          non_zero_delta ? blink::WebMouseWheelEvent::kPhaseChanged
+                         : blink::WebMouseWheelEvent::kPhaseStationary;
+      mouse_wheel_end_dispatch_timer_.Reset();
+    }
+  }
+}
+
+void MouseWheelPhaseHandler::DispatchPendingWheelEndEvent() {
+  if (!mouse_wheel_end_dispatch_timer_.IsRunning())
+    return;
+
+  base::Closure task = mouse_wheel_end_dispatch_timer_.user_task();
+  mouse_wheel_end_dispatch_timer_.Stop();
+  task.Run();
+}
+
+void MouseWheelPhaseHandler::IgnorePendingWheelEndEvent() {
+  mouse_wheel_end_dispatch_timer_.Stop();
+}
+
+void MouseWheelPhaseHandler::SendSyntheticWheelEventWithPhaseEnded(
+    blink::WebMouseWheelEvent last_mouse_wheel_event,
+    bool should_route_event) {
+  DCHECK(host_view_->wheel_scroll_latching_enabled());
+  blink::WebMouseWheelEvent mouse_wheel_event = last_mouse_wheel_event;
+  mouse_wheel_event.delta_x = 0;
+  mouse_wheel_event.delta_y = 0;
+  mouse_wheel_event.phase = blink::WebMouseWheelEvent::kPhaseEnded;
+  mouse_wheel_event.dispatch_type =
+      blink::WebInputEvent::DispatchType::kEventNonBlocking;
+  if (should_route_event) {
+    host_->delegate()->GetInputEventRouter()->RouteMouseWheelEvent(
+        host_view_, &mouse_wheel_event,
+        ui::LatencyInfo(ui::SourceEventType::WHEEL));
+  } else {
+    host_view_->ProcessMouseWheelEvent(
+        mouse_wheel_event, ui::LatencyInfo(ui::SourceEventType::WHEEL));
+  }
+}
+
+void MouseWheelPhaseHandler::ScheduleMouseWheelEndDispatching(
+    blink::WebMouseWheelEvent wheel_event,
+    bool should_route_event) {
+  mouse_wheel_end_dispatch_timer_.Start(
+      FROM_HERE,
+      base::TimeDelta::FromMilliseconds(
+          kDefaultMouseWheelLatchingTransactionMs),
+      base::Bind(&MouseWheelPhaseHandler::SendSyntheticWheelEventWithPhaseEnded,
+                 base::Unretained(this), wheel_event, should_route_event));
+}
+
+}  // namespace content