How to write a Firefox extension that would open an html popup window (a la Chrome)?

Question

JavaScript

I honestly and for a long time tried to do it myself. But it didn't work, I need the audience's help :-)
There are extensions for Chrome, Safari & Opera for my vPass (they were easy to write). Asking for Firefox too, but how? I read all over the Internet, I did not understand anything.

Maybe you, dear reader, have experience in creating a firefox extension that would:
1) add a button to the toolbar, when pressed,
2) open a popup with some html page, like this -



Thank you!

Answer 1

1. Find a similar simple extension , study its code. ;-)
2. Go to the section of the Mozilla Developer Network dedicated to creating add-ons.

Answer 2

Of the extensions with similar functions that I once worked with, there is " Plug-in χ·tools for Firefox 3.6 ". The API, most likely, has changed, since the 4th version it did not work.