The things that make it safe to run that code will significantly negatively impact image decoding speed right now. That's not necessarily a fundamental problem with the universe, but it's a true statement at the moment.
And that's accepting that WASM is safe, which I do not axiomatically accept. History suggests that I am very safe in claiming that most implementations will end up with some catastrophic-level security vulnerabilities in them before all's said and done.
> The things that make it safe to run that code will significantly negatively impact image decoding speed right now.
Okay, but as I said before, for specific cases we can still do things the old way. I.e., upon decoding we detect that the url points to a known format, and we run the fast+safe decoder. For unknown formats, we download the slow decoder and use that. This way, we have more than what we would otherwise have (flexibility). And in the future, WASM will be faster anyway. I only see benefits. Of course, the sandbox should be formally proved correct first.
What's your threshold for significance on image decoding speed? I bet making it 4x slower would be negligible in the vast majority of cases.
The computational power you need for image decoding is extremely narrow and easy to make safe. You need some mathematical operations and some loops. You don't need any APIs or data structures. Mask off all the pointers and you can have have a provably safe interpeter/compiler that runs pretty fast.
Remember that 4x slower means (at least) 4x worse battery drain on a phone. In the modern internet there basically is never any excuse to waste resources.
But it's also on a phone where saving data transfer can give you huge battery benefits. And it's not intentional waste; having this fallback doesn't stop browsers from adding native decoders.
And that's accepting that WASM is safe, which I do not axiomatically accept. History suggests that I am very safe in claiming that most implementations will end up with some catastrophic-level security vulnerabilities in them before all's said and done.