I have an old-platform Java Applet-based emulator which works very well. There is some analogs written in JS+Canvas, but it looks very bad (very dirty realtime, many functions doesn't work, many hardware not emulated).
The only problem of Java Applet is impossibility to show something over it in web page. I get an idea to replace original Java Canvas by HTML5 Canvas and use existing Applet to work with it.
Is it possible? If yes, what drawbacks can be there? What other technologies you can propose to develop integrated-to-webpage emulator? (NES, Playstation, etc)