Mozilla Labs announced its fourth in a regular series of releases for their open source Jetpack SDK.
"The intent of the Jetpack SDK is to provide enough APIs to enable the majority of functionality that existing add-ons require," Jetpack FAQ says. "If the Jetpack API doesn't provide the flexibility or feature you need, you'll be able to write your own module to add that capability."
Add-on developers using XUL are going to be encouraged to port their code to the web-based Jetpack SDK.
The newest Jetpack adds four "high-level" API's.
The page worker API makes it possible to for add-ons to create a hidden permanent frame that can load and access web pages.
The widget API offers a visually consistent way for add-ons to show themselves in the browser and interact with users.
To store persistent data that survives restarts Jetpack now has a simple storage API.
And, there's a private browsing API so add-on developers can detect the status of private browsing.