chromium/components/performance_manager/public/decorators/tab_page_decorator.h

// Copyright 2023 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef COMPONENTS_PERFORMANCE_MANAGER_PUBLIC_DECORATORS_TAB_PAGE_DECORATOR_H_
#define COMPONENTS_PERFORMANCE_MANAGER_PUBLIC_DECORATORS_TAB_PAGE_DECORATOR_H_

#include "base/memory/raw_ptr.h"
#include "base/observer_list.h"
#include "base/observer_list_types.h"
#include "base/sequence_checker.h"
#include "components/performance_manager/public/graph/graph.h"
#include "components/performance_manager/public/graph/graph_registered.h"
#include "components/performance_manager/public/graph/page_node.h"

namespace performance_manager {

class TabPageObserver;

// A decorator that adorns `PageNode`s with some data that allows it to provide
// a stable handle to a tab, even though the underlying `PageNode` associated
// with that tab might change due to tab discarding. Registering as an observer
// or using the `FromPageNode` function allows callers to obtain a pointer to a
// `TabHandle` object whose `page_node()` function always points to the
// `PageNode` associated with the tab.
class TabPageDecorator : public PageNode::ObserverDefaultImpl,
                         public GraphOwnedAndRegistered<TabPageDecorator> { … };

// A stable handle to a tab. Objects of this class are created when a `PageNode`
// becomes a tab, and are only destroyed when that tab is closed. During tab
// discarding, the `PageNode` returned by `page_node()` will change. Callers may
// store pointers to `TabHandle` objects until
// `TabPageObserver::OnBeforeTabRemoved` is called for said `TabHandle` object,
// and they are guaranteed that `page_node()` will return the `PageNode`
// associated with the tab.
class TabPageDecorator::TabHandle { … };

class TabPageObserver : public base::CheckedObserver { … };

class TabPageObserverDefaultImpl : public TabPageObserver { … };

}  // namespace performance_manager

#endif  // COMPONENTS_PERFORMANCE_MANAGER_PUBLIC_DECORATORS_TAB_PAGE_DECORATOR_H_