Refactor GestureNavigation to eliminate code redundancy

content/browser/web_contents/aura/overscroll_window_delegate.h

+// Copyright (c) 2015 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.
+
+#ifndef CONTENT_BROWSER_WEB_CONTENTS_AURA_OVERSCROLL_WINDOW_DELEGATE_H_
+#define CONTENT_BROWSER_WEB_CONTENTS_AURA_OVERSCROLL_WINDOW_DELEGATE_H_
+
+#include "content/browser/renderer_host/overscroll_controller.h"
+#include "content/browser/web_contents/aura/overscroll_navigation_overlay.h"
+#include "content/browser/web_contents/web_contents_impl.h"
+#include "ui/aura_extra/image_window_delegate.h"
+
+namespace content {
+
+// The window delegate for the overscroll window. This processes UI trackpad and
+// touch events and converts them to overscroll event. The delegate destroys
+// itself when the window is destroyed.
+class OverscrollWindowDelegate : public aura_extra::ImageWindowDelegate {
+ public:
+  OverscrollWindowDelegate(OverscrollControllerDelegate* delegate,
+                           const gfx::Image& image);
+
+ private:
+  ~OverscrollWindowDelegate() override;
+
+  // Starts the overscroll gesture.
+  void StartOverscroll();
+
+  // Resets the overscroll state.
+  void ResetOverscroll();
+
+  // Completes or resets the overscroll from the current state.
+  void CompleteOrResetOverscroll();
+
+  // Updates the current horizontal overscroll.
+  void UpdateOverscroll(float delta_x);
+
+  // Overridden from ui::EventHandler.
+  void OnKeyEvent(ui::KeyEvent* event) override;
+  void OnMouseEvent(ui::MouseEvent* event) override;
+  void OnScrollEvent(ui::ScrollEvent* event) override;
+  void OnGestureEvent(ui::GestureEvent* event) override;
+
+  // Delegate to which we forward overscroll events.
+  OverscrollControllerDelegate* delegate_;
+
+  // The current overscroll mode.
+  OverscrollMode overscroll_mode_;
+
+  // The latest delta_x scroll update.
+  float delta_x_;
+
+  // The ratio of overscroll at which we consider the overscroll completed.
+  const float complete_threshold_ratio_;
+
+  // The threshold for starting the overscroll gesture, for touchscreen or
+  // touchpads.
+  const float start_threshold_touchscreen_;
+  const float start_threshold_touchpad_;
+
+  // The threshold for starting the overscroll gesture for the current touch
+  // input.
+  float active_start_threshold_;
+
+  DISALLOW_COPY_AND_ASSIGN(OverscrollWindowDelegate);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_WEB_CONTENTS_AURA_OVERSCROLL_WINDOW_DELEGATE_H_