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Observer Notifications 编辑

Observer topics

The following are topics that you can observe during the course of an application. Unless otherwise noted you register for the topics using the nsIObserverService.

Application startup

These are the topics that you can observe on startup, in order of appearance.

If your component requires access to the user profile, or any services which require access to the profile (preferences, bookmarks, and so on) then a common pattern is to register with the nsICategoryManager for the app-startup topic which can be done in the component's registration code, and then in that notification register with the observer service for the profile-after-change notification. See Receiving startup notifications for more information about how this works.

Starting in Firefox 3.5 components can simply register for the profile-after-change notification in nsICategoryManager.

Topic	Description
*	Everything. [nsObserverService.cpp]

Topic	Description
xpcom-startup	Note: An extension can no longer be registered to receive this notification in Firefox 4 and later. See XPCOM changes in Gecko 2.0 for details. Called when xpcom is initialized. Many things are not available for use at this point. To receive this notification you have to register with `nsICategoryManager`. The registered component is always retrieved as a singleton (That is getService() will be used to instantiate it).
app-startup	Note: An extension can no longer be registered to receive this notification in Firefox 4 and later. See XPCOM changes in Gecko 2.0 for details. General event for application startup. To receive this notification you have to register with `nsICategoryManager`. Prepend "service," to the contract ID in the category registration to be invoked via getService() instead of createInstance().
profile-do-change	This is fired after the profile has been selected. You will not be able to access user preferences, bookmarks, or anything that uses the profile folder until this event occurs. This occurs after any profile migration.
profile-after-change	This is fired after all the observers for profile-do-change have been notified. You can register with `nsICategoryManager` to receive this notification. Prior to Firefox 3.5, this was available to observers observing the app-startup/xpcom-startup notification.
final-ui-startup	Triggered just before the first window for the application is displayed.
sessionstore-windows-restored	Sent by the session restore process to indicate that all initial browser windows have opened. Note that while the window are open and the chrome loaded the tabs in the windows may still be being restored after this notification. Note: This notification is specific to Firefox and SeaMonkey 2.0 applications

Application shutdown

These are the topics that you can observe on shutdown, in order of appearance.

Topic	Description
quit-application-requested	Something has requested that the application be shutdown. You can cancel the shutdown from here by setting `aSubject.data` to `true` (`aSubject` is the first parameter to your observer, the data value is an `nsISupportsPRBool`).
quit-application-granted	All observers have agreed to the shutdown.
quit-application	The application is about to quit. This can be in response to a normal shutdown, or a restart. Note: The data value for this notification is either 'shutdown' or 'restart'.
profile-change-net-teardown	The network connection is going offline at this point. Note: The data value for this notification is always 'shutdown-persist'.
profile-change-teardown	Part of the shutdown, profile data is still available at this point. Note: The data value for this notification is always 'shutdown-persist'.
profile-before-change	Called just before the profile is lost. Note: The data value for this notification is always 'shutdown-persist'.
profile-before-change-qm	Called to shut down the QuotaManager; this is separated from profile-before-change to allow everything inside profile-before-change to continue using it.
profile-before-change-telemetry	Called to shut down telemetry, again separated to allow everything before this event to continue using it.
xpcom-will-shutdown	Called just before xpcom-shutdown. Observer must not spin event loop.
xpcom-shutdown	Assortment of critical services stop operating. Many things will not be available here.
web-workers-shutdown	Called inside xpcom-shutdown. This shuts down all web workers.
xpcom-shutdown-threads	Shuts down the thread manager, causing all nsThreads to finish processing any events already queued and stop accepting new events.

Browser

These topics indicate interesting things that happen that the browser alerts you to.

Topic	Description
browser:purge-session-history	Sent when the sanitizer runs to purge all history and other information.
browser:purge-domain-data	Sent after domain-specific history and other information have been purged. The data value is a string form of the domain.
browser-lastwindow-close-requested	Sent when the browser wishes to close the last open browser window. When this is sent, it is possible that other windows may still be open, such as the download manager or preferences. The data value is an `nsISupportsPRBool`. Recipients may set this to `true` to abort the close.
browser-lastwindow-close-granted	Sent when all interested parties have responded to the browser-lastwindow-close-requested notification and none of them requested that the close be aborted. After this is sent and handled, the browser window will close.
browser-delayed-startup-finished	Sent when the browser window and all its components have been loaded and initialized.

Documents

These topics indicate notifications you can monitor related to DOM documents.

Topic	Subject	Data	Description
chrome-document-global-created	`nsIDOMWindow`	null	Sent immediately after a chrome document window has been set up, but before any script code has been executed. This lets extensions inject API into chrome windows as needed (see nsIDOMGlobalPropertyInitializer for an alternative method of doing this, which uses significantly less memory). `data` is intentionally left blank.
content-document-global-created	`nsIDOMWindow`	origin	Sent immediately after a web content document window has been set up, but before any script code has been executed. This lets extensions inject API into content windows as needed (see nsIDOMGlobalPropertyInitializer for an alternative method of doing this). `data` is a string form of the origin (for use in security checks), eg "http://developer.mozilla.org".
document-element-inserted	`Document`	null	Sent immediately after the root element of a document has been created, but before executing any script on it.
user-interaction-active	`nsIDOMWindow`	null	Sent once every 5000ms while this chrome document sees some kind of user activity (for example, keyboard or mouse events), and at the exact moment of the state transition from idle to active.
user-interaction-inactive	`nsIDOMWindow`	null	Sent when the chrome document has seen no user activity for a while. The notification is not repeated during a continuous inactivity period.

Windows

These topics indicate points of interest during the lifetime of a window.

Topic	Subject	Description
dom-window-destroyed	`nsIDOMWindow`	Called just before a DOM window is destroyed.
inner-window-destroyed	`nsIDOMWindow`	Called when an inner window is removed from the backward/forward cache. See Working With BFCache for information about the bfcache, and Inner and outer windows for details about how the window hierarchy works. Extensions that cache information about windows may wish to observe this so they can release information when the window is destroyed. The window id can be obtained from subject.QueryInterface(Components.interfaces.nsISupportsPRUint64).data
outer-window-destroyed	`nsIDOMWindow`	Called when an outer window is disconnected from its docshell. See Inner and outer windows for details about how the window hierarchy works. Extensions that cache information about windows may wish to observe this so they can release information when the window is destroyed. The window id can be obtained from subject.QueryInterface(Components.interfaces.nsISupportsPRUint64).data
toplevel-window-ready	`nsIWindowWatcher`	Called just after a new top level window has been opened and is ready, but has not yet loaded a document.
xul-window-destroyed		Called just before a XUL window is destroyed.
xul-window-registered	`nsIAppWindow`	Called just after a top level XUL window is registered with the window mediator service.
xul-window-visible	`nsIAppWindow`	Called just after a XUL window is made visible.
browsing-context-discarded	`BrowsingContext`	Called while a BrowsingContext is being discarded. By this point, the BrowsingContext will have been detached from its BrowsingContextGroup and parent WindowContext, and removed from any BrowsingContext tree it was a part of. This is sent before BrowsingContext::Closed() is updated.
window-global-created	`WindowGlobalParent`	Called just after a WindowGlobalParent is initialized. A WindowGlobal actor has a lifetime matching that of an nsGlobalWindowInner.
window-global-destroyed	`WindowGlobalParent`	Called just before a WindowGlobalParent is destroyed. By this point, the WGP being destroyed will have cleaned up most of its state, including its BrowsingContext children and JSWindowActors. Additionally, it will have been removed from any WindowContext tree it was part of.

IO Notifications

These topics can be used to watch the IO service for useful information.

Topic	Description
offline-requested	Called to query whether the application can go offline. The attempt to go offline can be canceled. Note: If your code chooses to cancel the attempt to go offline, it must notify the user.
network:offline-about-to-go-offline	Called just before all network IO is taken offline.
network:offline-status-changed	Called when the offline state has changed. Note: The data value for this notification 'offline' or 'online' to indicate the new state.
network:link-status-changed	Called when the network link status changes.

HTTP requests

These are the topics that you can observe during a HTTP request (see Setting HTTP request headers and Creating Sandboxed HTTP Connections). Both are passed an nsIHttpChannel as the subject parameter.

Topic	Description
http-on-modify-request	Called as a http request is made. The channel is available to allow you to modify headers and such. See this code snippet to learn how to get the tab that issued the request.
http-on-opening-request	Similar to http-on-modify-request, but called earlier (synchronously during the channel's asyncOpen() call), and some channel attributes (proxyInfo) may be missing. Use only if your observer must be called before asyncOpen returns.
http-on-examine-response	Called after a response has been received from the web server. Headers are available on the channel. The response can be accessed and modified via nsITraceableChannel.
http-on-examine-cached-response	Called instead of http-on-examine-response when a response will be read completely from the cache. Headers are available on the channel.
http-on-examine-merged-response	Called instead of http-on-examine-response when a response will be read partially from cache, and partially from the network (HTTP 206 or 304 response). Headers are available on the channel.

Cookies

These topics indicate whenever a cookie has been changed (added, changed, cleared, or deleted) or its setting rejected by the browser. See nsICookieService for details.

Topic	Description
cookie-changed	Called upon a cookie change (added, changed, cleared, or deleted)
cookie-rejected	Called when the setting of a cookie was rejected by the browser (per the user's preferences)
http-on-response-set-cookie	This is fired only when a cookie is created due to the presence of `Set-Cookie` header in the response header of any network request. This notification will come only after the "http-on-examine-response" is fired, but it will not always appear.

Download Manager

These topics indicate that events related to the Download Manager have occurred.

Topic	Description
download-manager-ui-done	Called when the list of downloads in the Download Manager windows finishes updating. This can happen multiple times, such as when the window first opens, when multiple items are removed, and when entering private browsing mode.
download-manager-remove-download	Called when a download of the list is removed or all the list is cleared. The subject will be the download id wrapped in `nsISupportsPRUint32`, for one download removed, or null for multi download remove, for example when the download list is cleared.

Extension Manager

Note: These notifications are no longer available starting with Gecko 2.0, instead use AddonManager.addAddonListener() to receive similar events.

This topic indicates when the extension manager performs some action. Note that any action will be taken the next time the application starts. See nsIExtensionManager for details.

Topic	Data	Description
em-action-requested	item-installed	A new extension has been installed.
em-action-requested	item-upgraded	A different version of an existing extension has been installed.
em-action-requested	item-uninstalled	An addon has been marked to be uninstalled.
em-action-requested	item-enabled	An addon has been enabled.
em-action-requested	item-disabled	An addon has been disabled.
em-action-requested	item-cancel-action	A previous action has been cancelled.

Idle Service

This topic indicates when actions related to the Idle Service, provided by the nsIIdleService interface. Unlike the user-interaction-active and user-interaction-inactive topics listed above, the Idle Service monitors user activity in general, whether related to the Mozilla application or not (acting somewhat like the user activity/inactivity events a screen saver would be interested in).

Topic	Data	Description
idle	The length of time the user has been idle, in milliseconds.	Sent when the user becomes idle.
idle-daily	The length of time the user has been idle, in milliseconds.	Sent once a day while the user is idle.
back	The length of time the user has been idle, in milliseconds.	Sent when the user returns from being idle.

Computer sleep and wake

This topic indicates when actions related to the computer going to sleep or waking up occur. (Note: these notifications are not currently available on Linux. See bug 758848.)

Topic	Data	Description
sleep_notification	null	Sent when the computer is going to sleep.
wake_notification	null	Sent when the computer is waking up.

Login Manager

This topic indicates when actions related to the Login Manager occur.

Topic	Data	Description
passwordmgr-found-form	noAutofillForms	A login is available for this form, but autofill of forms is disabled, so the form was not automatically filled out.
passwordmgr-found-form	autocompleteOff	A login is available for this form, but autocomplete is disabled.
passwordmgr-storage-changed	addLogin	A login has been added to the Login Manager's database. The notification's subject is the login that was added to the database.
passwordmgr-storage-changed	removeLogin	A login was removed from the Login Manager's database. The notification's subject is the login that was removed from the database.
passwordmgr-storage-changed	modifyLogin	A login in the Login Manager's database was modified. The notification's subject is an array whose first entry is the old login and whose second entry is the new one.
passwordmgr-storage-changed	removeAllLogins	All logins have been removed from the Login Manager's database.
passwordmgr-storage-changed	hostSavingEnabled	Host saving has been enabled.
passwordmgr-storage-changed	hostSavingDisabled	Host saving has been disabled.

Places

This topic indicates when actions related to Places (the history and bookmarks database) occur.

Topic	Data	Description
places-autocomplete-feedback-updated		Sent when Places updates the location bar's autocompletion display.
places-connection-closed		Sent after Places has closed its database connection. Once this has been sent, no Places features will work.
places-connection-closing		Sent as the last notification before the Places service closes its database connection. Warning: This is for internal use only.
places-database-locked		The Places database is currently locked by a third-party process and cannot be opened.
places-favicons-expired		Sent when all favicons have been expired.
places-init-complete		The Places database has been successfully initialized. You should wait until this notification occurs before querying the places database.
places-maintenance-finished		Sent when maintenance of the Places database is complete; this is done periodically in the background to keep the Places database tidy.
places-shutdown		Sent when Places shuts down. If you are referencing instances of `mozIStorageStatement` referencing Places databases when this notification occurs, you should call their `mozIStorageStatement.finalize()` method
places-sync-finished		Sent when the Places database has been successfully flushed to disk.
places-will-close-connection		Sent when the Places service is about to close its database connection. Only necessary cleanup tasks should run at this point, and nothing should be added to the database. In addition, after this has been sent, no Places APIs should be called. Warning: This is for internal use only.

Session Store

These topics are used when actions related to Session Store occur.

Topic	Data	Description
sessionstore-state-read		Sent immediately after session store data is read and before it's used.
sessionstore-state-finalized		Sent immediately after the session is restored.
sessionstore-state-write		Sent immediately before the session store data is written to disk.
sessionstore-state-write-complete		Sent immediately after the session store data is written to disk.
sessionstore-state-purge-complete

Private browsing

These topics indicate when actions related to private browsing occur.

Topic	Data	Description
private-browsing	enter	Sent when private browsing mode is activated.
private-browsing	exit	Sent when private browsing mode is deactivated.

Bookmarks

These topics indicate when actions related to bookmarks occur.

Topic	Data	Description
bookmarks-restore-begin	json	Sent just before bookmarks are restored from JSON.
bookmarks-restore-begin	html	Sent just before bookmarks are restored from HTML. If bookmarks will be restored into a specific folder, observers will be passed an `nsISupportsPRInt64` through their subject parameters indicating the ID of the folder. The subject is null otherwise.
bookmarks-restore-begin	html-initial	Sent just before bookmarks are restored from HTML on initial import. If bookmarks are restored into a specific folder, observers will be passed an `nsISupportsPRInt64` through their subject parameters indicating the ID of the folder. The subject is null otherwise.
bookmarks-restore-success	json	Sent just after bookmarks are restored from JSON.
bookmarks-restore-success	html	Sent just after bookmarks are restored from HTML. If bookmarks were restored into a specific folder, observers will be passed an `nsISupportsPRInt64` through their subject parameters indicating the ID of the folder. The subject is null otherwise.
bookmarks-restore-success	html-initial	Sent just after bookmarks are restored from HTML on initial import. If bookmarks were restored into a specific folder, observers will be passed an `nsISupportsPRInt64` through their subject parameters indicating the ID of the folder. The subject is null otherwise.
bookmarks-restore-failed	json	Sent when bookmarks could not be sucessfully restored from JSON.
bookmarks-restore-failed	html	Sent when bookmarks could not be successfully restored from HTML. If bookmarks were to have been restored into a specific folder, observers will be passed an `nsISupportsPRInt64` through their subject parameters indicating the ID of the folder. The subject is null otherwise.
bookmarks-restore-failed	html-initial	Sent when bookmarks could not be successfully restored from HTML on intial import. If bookmarks were to have been restored into a specific folder, observers will be passed an `nsISupportsPRInt64` through their subject parameters indicating the ID of the folder. The subject is null otherwise.

Themes

These topics indicate when actions related to themes occur.

Topic	Data	Description
lightweight-theme-preview-requested	json	Sent when the user requests to preview a lightweight theme, but before existing windows are styled with the new theme.
lightweight-theme-change-requested	json	Sent to indicate that the user has chosen a new theme in the add-ons manager, but before the change takes effect.
lightweight-theme-changed	-	Sent after the current theme is changed.
lightweight-theme-styling-update	json	Sent when the current theme being used is changed; this is sent even when the user is previewing a theme, not just when the theme is actually selected.
lightweight-theme-list-changed	-	The list of available lightweight themes has changed.

Developer tools

These topics let you know about things that have happened related to Firefox's built-in developer tools.

Topic	Data	Description
highlighter-ready	-	Sent when the highlighter component is initialized. Note: This is used by the Inspector to detect when it should begin its initialization process.
inspector-closed	-	Sent when the Inspector tool is closed.
inspector-editor-closed	-	Sent after the attribute-value editor has been closed.
inspector-editor-opened	-	Sent after the attribute-value editor has been opened and initialized.
inspector-editor-saved	-	Sent when changes have been saved in the attribute-value editor.
inspector-highlighting	-	Sent every time a different node in the page gets highlighted.
inspector-opened	-	Sent after the Inspector tool has finished its initialization.
inspector-ruleview-ready	-	Sent when the inspector's CSS Rule View is opened and initialized.
inspector-state-restored	-	Sent when the Inspector is re-opened after a tab switch.
inspector-treepanel-ready	-	Sent when the Inspector's Tree Panel is opened and initialized.
inspector-unhighlighting	-	Sent every time the highlighter stops highlighting a node.
remote-listening	string	Sent after when the remote agent is listening for incoming connections after `RemoteAgent.listen()` is called. The data is a string containing a fully qualified URL to the main target’s WebSocket endpoint.

Telemetry

gather-telemetry

Note: This is obsolete and planned to be removed as it's not firing at the proper times.

Sent by the telemetry service when it's time to start gathering telemetry data, since the telemetry ping is coming soon.

Plugins

Topic	Data	Description
plugin-crashed	-	Sent when a plugin has crashed.

Message manager

Topic Subject Data Description

message-manager-disconnect

Topic	Subject	Data	Description
message-manager-disconnect	`nsIContentFrameMessageManager`	null	This notification is sent when a message manager disconnects. The subject of the notification is the message manager that disconnected.

nsIContentFrameMessageManager

null

This notification is sent when a message manager disconnects.

The subject of the notification is the message manager that disconnected.

If you're using a message manager to communicate with a script that may be running in a different process, you might need to know when the message manager has disconnected from the other end of the conversation, so you can stop sending it messages or expecting to receive messages.

For example, suppose you've loaded a frame script into a tab using a browser message manager, and the user closes the tab. The frame script is unloaded and the browser message manager disconnects from it. By listening for message-manager-disconnect you will be informed when this happens.

Permission Manager

Topic Subject Data Description

perm-changed

Topic	Subject	Data	Description
perm-changed	`nsIPermission`	"deleted"/"added"/"changed"/"cleared"	This notification is sent when a permission changes. The subject of the notification is the permission object.

nsIPermission

"deleted"/"added"/"changed"/"cleared"

This notification is sent when a permission changes.

The subject of the notification is the permission object.

Context menu

Topic Subject Data Description

content-contextmenu

Topic	Subject	Data	Description
content-contextmenu	An object containing two properties: event The event that triggered the context menu. addonInfo An empty object that add-ons can use to send data to the main process.	null	This notification is sent when the context menu is displayed. It is sent, and received, in the content process: you can't listen to it in the chrome process. It's used by the `context-menu` module in the Add-on SDK, to help send information to the `context-menu` code running in the chrome process when a context menu is displayed.

An object containing two properties:

event: The event that triggered the context menu.
addonInfo: An empty object that add-ons can use to send data to the main process.

null

This notification is sent when the context menu is displayed. It is sent, and received, in the content process: you can't listen to it in the chrome process.

It's used by the context-menu module in the Add-on SDK, to help send information to the context-menu code running in the chrome process when a context menu is displayed.

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