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_CHROME_BROWSER_UI_FULLSCREEN_FULLSCREEN_CONTROLLER_H_
#define IOS_CHROME_BROWSER_UI_FULLSCREEN_FULLSCREEN_CONTROLLER_H_

#import <Foundation/Foundation.h>

#include "base/macros.h"
#include "components/keyed_service/core/keyed_service.h"

@class ChromeBroadcaster;
class FullscreenControllerObserver;
class WebStateList;

// 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 KeyedService {
 public:
  explicit FullscreenController() = default;

  // The ChromeBroadcaster through the FullscreenController receives UI
  // information necessary to calculate fullscreen progress.
  // TODO(crbug.com/790886): Once FullscreenController is a BrowserUserData,
  // remove this ad-hoc broadcaster and drive the animations via the Browser's
  // ChromeBroadcaster.
  virtual ChromeBroadcaster* broadcaster() = 0;

  // The WebStateList for the Browser whose fullscreen state is managed by this
  // controller.
  // TODO(crbug.com/790886): Once FullscreenController is a BrowserUserData,
  // remove this, as the Browser's WebStateList can be used directly rather than
  // being set.
  virtual void SetWebStateList(WebStateList* web_state_list) = 0;

  // Adds and removes FullscreenControllerObservers.
  virtual void AddObserver(FullscreenControllerObserver* observer) = 0;
  virtual void RemoveObserver(FullscreenControllerObserver* observer) = 0;

  // 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.
  virtual bool IsEnabled() const = 0;
  virtual void IncrementDisabledCounter() = 0;
  virtual void DecrementDisabledCounter() = 0;

 private:

  DISALLOW_COPY_AND_ASSIGN(FullscreenController);
};

#endif  // IOS_CHROME_BROWSER_UI_FULLSCREEN_FULLSCREEN_CONTROLLER_H_