While this is impressive, I find it surprisingly slow compared to much more demanding applications with bigger code bases compiled via Emscripten. Any ideas why?
Well, I don't know what you mean by slow, but it could be the use of setTimeout() every 10ms to simulate[1] Vim's synchronous busy-wait is affecting responsiveness.
Lu mentioned[2] on vim_dev that it was necessary to write a hack for this portion.
Yeah, I hit this same road-block when trying to port vim to JS and gave up because it didn't seem worth it after that. If only vim ran a regular event loop, it would have been such an easy port, compared to what they had to do here. When figuring out how I could overcome it, I remember reading accounts of KDE developers trying to embed vim into their widgets and failing over and over. In the end, there was a solution to "embed" vim with some special IPC the netbeans IDE developers put into vim, but you had to run vim as a separate process for that to work - which is not possible on the web as it stands today. The numerous synchronous busy-wait loops in vim killed all approaches I had considered, so kudos to these guys for figuring out a way, even if it's slow.
There's an event loop patch on vim_dev being played with. Maybe in the next 12 months we will see some action with that approach or the other "timers" approach submitted (and ignored by Bram) by the floobits devs.
