Route Scroll events through a cc::InputHandler

ui/compositor/overscroll/ui_input_handler.cc

+// Copyright 2016 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/compositor/overscroll/ui_input_handler.h"
+
+#include "base/logging.h"
+#include "cc/trees/layer_tree_impl.h"
+#include "cc/trees/scroll_node.h"
+#include "ui/events/event.h"
+
+namespace ui {
+
+namespace {
+
+// Creates a cc::ScrollState from a ui::ScrollEvent, populating fields general
+// to all event phases. Take care not to put deltas on beginning/end updates,
+// since InputHandler will DCHECK if they're present.
+cc::ScrollState CreateScrollState(const ScrollEvent& scroll, bool is_end) {
+  cc::ScrollStateData scroll_state_data;
+  scroll_state_data.position_x = scroll.x();
+  scroll_state_data.position_y = scroll.y();
+  if (!is_end) {
+    scroll_state_data.delta_x = -scroll.x_offset_ordinal();
+    scroll_state_data.delta_y = -scroll.y_offset_ordinal();
+  }
+  scroll_state_data.is_in_inertial_phase =
+      scroll.momentum_phase() == EventMomentumPhase::INERTIAL_UPDATE;
+  scroll_state_data.is_ending = is_end;
+  return cc::ScrollState(scroll_state_data);
+}
+
+}  // namespace
+
+UIInputHandler::UIInputHandler(
+    const base::WeakPtr<cc::InputHandler>& input_handler)
+    : input_handler_(input_handler.get()) {
+  input_handler_->BindToClient(this);
+}
+
+UIInputHandler::~UIInputHandler() {
+  DCHECK(!input_handler_);
+}
+
+void UIInputHandler::WillShutdown() {
+  input_handler_ = nullptr;
+}
+
+void UIInputHandler::Animate(base::TimeTicks time) {}
+
+void UIInputHandler::MainThreadHasStoppedFlinging() {}
+
+void UIInputHandler::ReconcileElasticOverscrollAndRootScroll() {}
+
+void UIInputHandler::UpdateRootLayerStateForSynchronousInputHandler(
+    const gfx::ScrollOffset& total_scroll_offset,
+    const gfx::ScrollOffset& max_scroll_offset,
+    const gfx::SizeF& scrollable_size,
+    float page_scale_factor,
+    float min_page_scale_factor,
+    float max_page_scale_factor) {}
+
+void UIInputHandler::DeliverInputForBeginFrame() {}
+
+void UIInputHandler::HandleScrollUpdate(const ScrollEvent& scroll,
+                                        cc::ElementId element) {
+  cc::ScrollState scroll_state = CreateScrollState(scroll, false);
+  scroll_state.data()->set_current_native_scrolling_element(element);
+  input_handler_->ScrollBy(&scroll_state);
+}
+
+void UIInputHandler::HandleScrollEnd(const ScrollEvent& scroll) {
+  cc::ScrollState scroll_state = CreateScrollState(scroll, true);
+  input_handler_->ScrollEnd(&scroll_state);
+}
+
+}  // namespace ui