Extension Manager:Bootstrapped Extensions: Difference between revisions

Extension Manager:Bootstrapped Extensions (view source)

Revision as of 15:05, 13 April 2010

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-__NOTOC__Bootstrapped add-ons exist as a means of restricting what is available to an add-on in order to allow it to be loaded and unloaded without restarting the application.
+__NOTOC__Bootstrapped add-ons exist as a means of restricting what is available to an add-on in order to allow it to be started up and shutdown without restarting the application.
-==Rationale==
+Current XPI add-ons cannot be removed from memory without restarting the application. This is because the features that we give them (XPCOM components, chrome registration and overlays etc.) cannot be removed in a managed fashion. Adding an add-on without a restart could possibly be implemented however that really only solves a small part of the problem as updates etc. would still require restarts.
-Current XPI add-ons cannot be unloaded without restarting the application. This is because the features that we give them (XPCOM components, chrome registration and overlays etc.) cannot be removed in a managed fashion. Loading without a restart could possibly be implemented however that really only solves a small part of the problem as updates etc. would still require restarts.
+The approach taken here is to simplify what it means to be an add-on. Instead of registering XPCOM components and chrome in bootstrapped add-ons we do nothing except execute a bootstrap script that the add-on provides, telling it to startup. The add-on can do whatever it likes at that point however it must undo anything it has done when we call the bootstrap script to tell it to shutdown.
-The approach taken here is to simplify what it means to be an add-on. Instead of registering XPCOM components and chrome in bootstrapped add-ons we instead do nothing except execute a bootstrap script when the add-on is loaded and call some functions on it. The add-on can do whatever it likes at that point however it must undo anything it has done when we call the bootstrap script to tell it to unload.
+==Starting up and Shutting down==
+A key feature of bootstrapped add-ons is that they must be able to be started and shutdown on demand by the platform. When told to startup it is up to the add-on's bootstrap code to do anything necessary to inject UI and behaviour into the application. When told to shutdown it is required that the add-on remove anything it has added and removing all references to its objects. Some examples of when startup and shutdown happen:
+* When first installed (if the add-on is compatible and enabled) the platform will tell the add-on to load.
+* When uninstalled (if the add-on is currently enabled) the platform will tell the add-on to unload.
+* When enabled or disabled while the application is running the platform will tell the add-on to startup or shutdown as appropriate.
+* When the application is started the platform will tell any enabled add-ons to startup.
+* When the user quits the application the platform will tell any enabled add-ons to shutdown.
 ==Declaring an Add-on as Bootstrappable==
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 ==Bootstrap Events==
-When an add-on is loaded the bootstrap.js file is executed in a privileged sandbox which is cached until the add-on is unloaded. The scripts should contain a number of functions that will be called to notify the add-on of certain events:
+Bootstrapped add-ons must provide a bootstrap.js file which defines main entry functions as defined below. When the platform needs to call a function the script will be loaded into a privileged sandbox which is cached until the add-on is shutdown.
 ===Startup===
-Whenever an add-on needs to be loaded the platform will call a function named <code>startup</code> in the bootstrap script. It will be passed the following arguments:
+Whenever an add-on needs to be started the platform will call a function named <code>startup</code> in the bootstrap script. It will be passed the following arguments:
 ;data :A JS object containing basic information about the add-on, <code>id</code>, <code>version</code> and <code>installPath</code>.
 ;reason :A number representing the reason for loading the add-on. This may be APP_STARTUP or ADDON_ENABLE.
+The add-on must at this point do anything necessary to make its functionality available, the platform will do nothing else to load the add-on.
 ===Shutdown===
-Whenever an add-on needs to be unloaded the platform will call a function named <code>shutdown</code> in the bootstrap script. It will be passed the following arguments:
+Whenever an add-on needs to be shutdown the platform will call a function named <code>shutdown</code> in the bootstrap script. It will be passed the following arguments:
 ;data :A JS object containing basic information about the add-on, <code>id</code>, <code>version</code> and <code>installPath</code>.
 ;reason :A number representing the reason for unloading the add-on. This may be APP_SHUTDOWN or ADDON_DISABLE.
+The add-on must at this point remove anything it has added to the application so its memory can be reclaimed.
 ===Install===