Extension Manager:Install Hooks: Difference between revisions

One of the more common issues that add-on developers seem to be hitting is trying to run code when their add-on is activated or deactivated. While there are currently ways to detect this they are not totally reliable and fail in many situations.

* Enabling (also runs during add-on installation)

* Disabling (also runs if an enabled add-on is uninstalled)

Only the hooks that the developer wishes to implement need to be included. A likely common case will be just the enable hook in order to perform some kind of first run behaviour like creating databases in the profile etc.

The ADDON structure may not be protected from being altered by the hook, however the structure will get thrown away after the hook is executed.

There are certain operations that need to be carefully protected from tampering with by hooks. In particular it should be close to impossible for a disable hook to be able to cancel that action. Hooks are not designed to decide whether the operation should proceed, they should perform simple actions in response to the operation.

Some consideration must be made whether to run hooks during safe mode or whether to potentially defer add-on changes until the next normal startup.

===Enable and upgrade===

These hooks will get executed in the early UI startup. Likely the final-ui-startup observer will be used to trigger them, though if a means of running them after the first UI windows are displayed is found then that would be a better choice.

===Disable===

The disable hook will run during early startup as the add-on is disabled/uninstalled. This hook should not expect to be able to display any UI. Shortly after the hook's execution the application's process will be restarted.

The first is due to implementation details. If the directory for the extension in the install location is removed, or if the registry key for the extension in the registry install location is removed then no disable hook will be executed.