ios/chrome/browser/ui/fullscreen/fullscreen_controller.h

// 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.

#ifndef IOS_CLEAN_CHROME_BROWSER_UI_FULLSCREEN_FULLSCREEN_CONTROLLER_H_
#define IOS_CLEAN_CHROME_BROWSER_UI_FULLSCREEN_FULLSCREEN_CONTROLLER_H_

#include <memory>

#include "base/macros.h"

class FullscreenControllerObserver;

// An object that observes scrolling events in the main content area and
// calculates how much of the toolbar should be visible as a result.  When the
// user scrolls down the screen, the toolbar should be hidden to allow more of
// the page's content to be visible.
class FullscreenController {
 public:
  explicit FullscreenController();
  ~FullscreenController();

  // Adds and removes FullscreenControllerObservers.
  void AddObserver(FullscreenControllerObserver* observer);
  void RemoveObserver(FullscreenControllerObserver* observer);

  // FullscreenController can be disabled when a feature requires that the
  // toolbar be fully visible.  Since there are multiple reasons fullscreen
  // might need to be disabled, this state is represented by a counter rather
  // than a single bool.  When a feature needs the toolbar to be visible, it
  // calls IncrementDisabledCounter().  After that feature no longer requires
  // the toolbar, it calls DecrementDisabledCounter().  IsEnabled() returns
  // true when the counter is equal to zero.  ScopedFullscreenDisabler can be
  // used to tie a disabled counter to an object's lifetime.
  bool IsEnabled() const;
  void IncrementDisabledCounter();
  void DecrementDisabledCounter();

 private:
  DISALLOW_COPY_AND_ASSIGN(FullscreenController);
};

#endif  // IOS_CLEAN_CHROME_BROWSER_UI_FULLSCREEN_FULLSCREEN_CONTROLLER_H_