chromium/chrome/browser/ui/tabs/tab_strip_model_observer.h

// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CHROME_BROWSER_UI_TABS_TAB_STRIP_MODEL_OBSERVER_H_
#define CHROME_BROWSER_UI_TABS_TAB_STRIP_MODEL_OBSERVER_H_

#include <memory>
#include <optional>
#include <set>
#include <vector>

#include "base/memory/raw_ptr.h"
#include "chrome/browser/ui/tabs/tab_change_type.h"
#include "components/sessions/core/session_id.h"
#include "components/tab_groups/tab_group_id.h"
#include "components/tab_groups/tab_group_visual_data.h"
#include "third_party/perfetto/include/perfetto/tracing/traced_value_forward.h"
#include "ui/base/models/list_selection_model.h"

class TabStripModel;

namespace content {
class WebContents;
}

namespace tabs {
class TabModel;
}

////////////////////////////////////////////////////////////////////////////////
//
// TabStripModelChange / TabStripSelectionChange
//
// This observer is not appropriate for most use cases. It's primarily used for
// features that must directly interface with the tab strip, for example: tab
// groups, tab search, etc.
// Most features in Chrome need to hold state on a per-tab basis. In that case,
// add a controller to TabFeatures and use TabInterface to observe for the tab
// events.
//
// The following class and structures are used to inform TabStripModelObservers
// of changes to:
// 1) selection model
// 2) activated tab
// 3) inserted/removed/moved tabs.
// These changes must be bundled together because (1) and (2) consist of indices
// into a list of tabs [determined by (3)]. All three must be kept synchronized.
//
////////////////////////////////////////////////////////////////////////////////
class TabStripModelChange { … };

// Struct to carry changes on selection/activation.
struct TabStripSelectionChange { … };

// Struct to carry changes to tab groups. The tab group model is independent of
// the tab strip model, so these changes are not bundled with
// TabStripModelChanges or TabStripSelectionChanges.
struct TabGroupChange { … };

////////////////////////////////////////////////////////////////////////////////
//
// TabStripModelObserver
//
//  Objects implement this interface when they wish to be notified of changes
//  to the TabStripModel.
//
//  Two major implementers are the TabStrip, which uses notifications sent
//  via this interface to update the presentation of the strip, and the Browser
//  object, which updates bookkeeping and shows/hides individual WebContentses.
//
//  Register your TabStripModelObserver with the TabStripModel using its
//  Add/RemoveObserver methods.
//
////////////////////////////////////////////////////////////////////////////////
class TabStripModelObserver { … };

#endif  // CHROME_BROWSER_UI_TABS_TAB_STRIP_MODEL_OBSERVER_H_