Refactor GestureNavigation to eliminate code redundancy

content/browser/web_contents/aura/overscroll_window_animation.h

+// Copyright 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_ANIMATION_H_
+#define CONTENT_BROWSER_WEB_CONTENTS_AURA_OVERSCROLL_WINDOW_ANIMATION_H_
+
+#include "content/browser/renderer_host/overscroll_controller_delegate.h"
+#include "content/common/content_export.h"
+#include "ui/compositor/layer_animation_observer.h"
+
+namespace aura {
+class Window;
+}
+
+namespace ui {
+class Layer;
+class LayerAnimator;
+}
+
+namespace content {
+
+class ShadowLayerDelegate;
+class WebContentsImpl;
+
+// Manages the animations during an overscroll navigation by handling overscroll
+// events.
+class CONTENT_EXPORT OverscrollWindowAnimation
+    : public OverscrollControllerDelegate,
+      ui::ImplicitAnimationObserver {
+ public:
+  enum Direction { SLIDE_FRONT, SLIDE_BACK, SLIDE_NONE };
+
+  // Delegate class that interfaces with the window animation, responsible for
+  // navigation.
+  class Delegate {
+   public:
+    virtual ~Delegate() {}
+
+    // The following two functions create a slide window and transfer back its
+    // ownership.
+    virtual scoped_ptr<aura::Window> CreateFrontWindow() = 0;
+    virtual scoped_ptr<aura::Window> CreateBackWindow() = 0;
+
+    // Returns the live window that participates in the overscroll gesture.
+    virtual aura::Window* GetTargetWindow() const = 0;
+
+    // Called when we know the animation is going to complete successfully.
+    virtual void OnOverscrollCompleting() = 0;
+
+    // Called when the animation has been completed.
+    virtual void OnOverscrollCompleted(
+        scoped_ptr<aura::Window> window) = 0;
+
+    // Called when the overscroll gesture has been aborted.
+    virtual void OnOverscrollAborted() = 0;
+  };
+
+  explicit OverscrollWindowAnimation(Delegate* delegate);
+
+  ~OverscrollWindowAnimation() override;
+
+  // Returns true if we are currently handling a slide animation.
+  bool is_active() const { return !!window_; }
+
+  // Overridden from OverscrollControllerDelegate:
+  gfx::Rect GetVisibleBounds() const override;
+
+  bool OnOverscrollUpdate(float delta_x, float delta_y) override;
+
+  void OnOverscrollComplete(OverscrollMode overscroll_mode) override;
+
+  void OnOverscrollModeChange(OverscrollMode old_mode,
+                              OverscrollMode new_mode) override;
+
+ private:
+  // Starts the overscroll cancelled animation.
+  void CancelOverscroll();
+
+  // Moves the animated window according to the given scroll deltas. Returns
+  // true if the update moved the window.
+  bool UpdateForScroll(float delta_x);
+
+  // Returns a translation on the x axis for the given overscroll.
+  float GetTranslationForOverscroll(float delta_x);
+
+  // Returns the layer that is animated for the overscroll gesture.
+  ui::Layer* GetFrontLayer() const;
+
+  // ui::ImplicitAnimationObserver:
+  void OnImplicitAnimationsCompleted() override;
+
+  // Owns the new window created on the overscroll gesture.
+  scoped_ptr<aura::Window> window_;
+
+  // Shadow shown under the animated layer.
+  scoped_ptr<ShadowLayerDelegate> shadow_;
+
+  // Delegate that provides the animation target and handles navigation.
+  Delegate* delegate_;
+
+  // The current overscroll direction.
+  Direction direction_;
+
+  // Indicates if the current overscroll gesture has been cancelled.
+  bool overscroll_cancelled_;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_WEB_CONTENTS_AURA_OVERSCROLL_WINDOW_ANIMATION_H_