I port a Chrome extension to Firefox. Because the XUL-based API is quite different from Chrome API, so I use the new add-on SDK of firefox.
There is a interface called "widget" can be used to make a little icon button like "BrowserAction" of Chrome, but "widget" is on the bottom of window, "BrowserAction" is on the top right side of window.
Some firefox extensions, for example, GreaseMonkey , have widgets on the top right, so I'm asking how to implement it using add-on SDK, not XUL based API?