> But - XPIs that add a button to a toolbar, or modify a menu, *do* > modify files within existing .jar file do they not?
No they don't. (Correcting myself.) On further examination, I was unable to find any XPI that actually modified an existing file that was located with a .jar archive. Adding buttons to toolbars works by somehow (not quite sure of this yet) creating an extra folder tree that is "used" in some manner by Mozilla. > If you didn't mind being platform-specific you could execute > system commands or your own included zip utility to do the job. I may, then, just live with being platform-specific. Can you give me an example of code in install.js that would issue a system command? (I haven't found such a beast yet.) Sorry for the newbie questions here.
