Html5 on itch.io

Eryen · February 23, 2017, 10:31pm

anonymous_user_f0fea7ad · March 8, 2017, 4:28pm

I think the issue here is that itch.io has disabled dynamic code execution by enforcing what’s called Content Security Policy (CSP). For detailed info about that, read e.g. Content security policy

Parallel to that, Emscripten has adjusted to no longer use eval() in to avoid this issue (and also to optimize performance). That was this bug: EM_ASM() et al. should not eval() · Issue #2596 · emscripten-core/emscripten · GitHub. I believe UE 4.16 will have updated Emscripten which has this fix deployed.

Another way to work around is to get UE4 from source, and get latest Emscripten SDK, and build UE4 for HTML5 with the latest SDK manually. This is somewhat involved process though, mostly for internal developers, so might be more hassle than it’s worth.

A second way to hack to workaround could be to “staticalize” the eval() function, by looking at all the code that is passed to eval(), and having static code paths which execute that code. This requires some technical debugging work, and might be a bit hacky. I did do that successfully for one project that needed to deploy on Facebook, which had similar kind of issue. The broad strokes for doing that would be to redefined the eval() function in the main page html file, with the following:

eval = function(s) {
if (s === ‘s1’) {
s1;
} else if (s === ‘s2’) {
s2;
} else {
console.error(‘Attempted to eval "’ + s + ‘" but not yet supported!’);
}
}

and the idea is to find all the different strings s with which eval() is getting called, and create the blocks s1, s2, etc. for each of those strings. This might be a horrible thing to attempt, but technically that should work.

I’m not too familliar with itch.io, perhaps the cleanest way might be if they support disabling CSP on a page if it’s not desirable, that would be a simplest workaround for the time being.

Eryen · March 10, 2017, 6:10pm

I´ll try to wait a bit, maybe it will be simplier later. My project was for school and we made a compromise so I don´t need to get to work trough itch.io. It would be cool thou. Anyway thank you for trying to help, maybe it will help someone else :).