The extension withExEditor[1] can open the editor of your choice in its own window, optionally with a different editor config file. Your editor writes to a file in /tmp and on each write, the text in the input field or area in your browser is updated with the contents of the file. This is an advantage over Tridactyl, by the way, since in Tridactyl you have to close the editor in order to update the text inside the browser.
The title is misleading. The class was there all along, the NoClassDefFoundError was thrown because the class loader was closed when trying to load a class.
When I provide code for free I want to be treated with respect.
There's evidence that this is not always the case when working on the Linux Kernel.
Of course, when somebody introduces bugs, that's a problem and should be talked about.
But you can do that respectfully without sugarcoating the affair.
I get that the author is frustrated with false claims about Qt, but calling people working on open source software "hippie coders" is just an insulting misrepresentation harming any rational debate.
You can use Scala.js[1] to transpile your Scala code to JavaScript and have type safety between client and server. You don't need to use any frameworks if you use Scala's features on the client well.
[1]: https://github.com/asamuzaK/withExEditor