XUL Layout is gone
This was basically Electron before there was Electron.It was hoped that other people would follow the Mozilla Suite's (before Firefox, Mozilla's standard distro was an application suite containing a browser, email reader, chat client, and HTML editor) example and use JavaScript, XUL, and XPCOM to build cross-platform desktop applications. The last of those, XPCOM (Xross Platform COM), was Mozilla's take on Microsoft's Component Object Model, where you would write lower-level components in C or C++ (using the NSPR, Netscape Portable Runtime) that were callable from JavaScriptUnfortunately, virtually no one outside of Mozilla adopted the XUL/JS/XPCOM stack. One of the few I remember was ActiveState's Komodo IDE.I still regard it as a huge missed opportunity for Mozilla.