chromium/extensions/browser/extension_registry_observer.h

// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef EXTENSIONS_BROWSER_EXTENSION_REGISTRY_OBSERVER_H_
#define EXTENSIONS_BROWSER_EXTENSION_REGISTRY_OBSERVER_H_

#include "extensions/browser/uninstall_reason.h"

namespace content {
class BrowserContext;
}

namespace extensions {
class Extension;
class ExtensionRegistry;
enum class UnloadedExtensionReason;

// Observer for ExtensionRegistry. Exists in a separate header file to reduce
// the include file burden for typical clients of ExtensionRegistry.
//
// There are separate event categories for loading (the OnExtensionLoaded,
// OnExtensionReady and OnExtensionUnloaded events) and installing (the
// OnExtensionWillBeInstalled, OnExtensionInstalled and OnExtensionUninstalled)
// extensions.
//
// For example, comparing OnExtensionLoaded and OnExtensionInstalled,
// OnExtensionLoaded is called whenever an extension is added to the "enabled"
// set of the extension registry. This includes:
//
//  - Extensions being loaded at Chrome startup.
//  - Extensions being reloaded:
//    * as part of an update.
//    * from a crash.
//    * from a disabled state (if the user toggled disabled -> enabled).
//    * as part of internal bookkeeping (we reload extensions on file access
//      being granted, for instance).
//    * if the extension requested it (chrome.runtime.reload()).
//    * probably others.
//  - New extensions being loaded for the first time (as part of installation).
//
// OnExtensionInstalled is called when a *new* extension is added, *or* when an
// extension is updated to a *new* version. It is not called for existing
// extensions being loaded at startup, etc. In a common run of Chrome, you
// probably won't get many "OnInstalled" events.
//
// As a general rule, most sites should observe OnExtensionLoaded, because they
// want to see "what are the enabled extensions".
class ExtensionRegistryObserver { … };

}  // namespace extensions

#endif  // EXTENSIONS_BROWSER_EXTENSION_REGISTRY_OBSERVER_H_