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// Copyright 2017 The Cobalt Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#ifndef COBALT_PAGE_VISIBILITY_PAGE_VISIBILITY_STATE_H_
#define COBALT_PAGE_VISIBILITY_PAGE_VISIBILITY_STATE_H_
#include "base/observer_list.h"
#include "cobalt/base/application_state.h"
#include "cobalt/page_visibility/visibility_state.h"
namespace cobalt {
namespace page_visibility {
// The visibility state of the Window and Document as controlled by the current
// application state.
class PageVisibilityState {
public:
// Pure virtual interface for classes that want to observe page visibility
// state changes.
class Observer : public base::CheckedObserver {
public:
// Called when the window focus state changes.
virtual void OnWindowFocusChanged(bool has_focus) = 0;
// Called when the VisibilityState changes.
virtual void OnVisibilityStateChanged(VisibilityState visibility_state) = 0;
protected:
virtual ~Observer() {}
};
PageVisibilityState();
explicit PageVisibilityState(
base::ApplicationState initial_application_state);
base::ApplicationState application_state() const {
return application_state_;
}
// Whether the current window has focus based on the current application
// state.
bool HasWindowFocus() const;
// Whether the current window has focus based on the current application
// state.
VisibilityState GetVisibilityState() const;
// Sets the current application state, and dispatches appropriate observation
// events.
void SetApplicationState(base::ApplicationState state);
// Adds a PageVisibiltyState::Observer to this PageVisibilityState.
void AddObserver(Observer* observer) { observer_list_.AddObserver(observer); }
// Removes a PageVisibiltyState::Observer from this PageVisibilityState, if it
// is registered.
void RemoveObserver(Observer* observer) {
observer_list_.RemoveObserver(observer);
}
// Returns whether a PageVisibiltyState::Observer is registered on this
// PageVisibilityState.
bool HasObserver(Observer* observer) const {
return observer_list_.HasObserver(observer);
}
// Clears all registered PageVisibiltyState::Observers, if any.
void ClearObservers() { observer_list_.Clear(); }
private:
void DispatchWindowFocusChanged(bool has_focus);
void DispatchVisibilityStateChanged(VisibilityState visibility_state);
// The current application state.
base::ApplicationState application_state_;
// The list of registered PageVisibiltyState::Observers;
base::ObserverList<Observer> observer_list_;
};
} // namespace page_visibility
} // namespace cobalt
#endif // COBALT_PAGE_VISIBILITY_PAGE_VISIBILITY_STATE_H_