web-sys question: Why do some OpenGL methods require mutable slices when they could be immutable?

[bgourlie]

See uniform_matrix4fv_with_f32_array docs as an example

The slice being passed shouldn't need to be mutable, so I'm curious why this is the case. Does this have to do with making safe assumptions with regard to mutability because Web IDL doesn't specify?

Edit: Also, if there is a more appropriate place to be asking these questions, please let me know!

[alexcrichton]

A good question! This is an unfortunate pessimization we have to perform. We don't actually know if JS will read or write the buffer that we pass out, so we have to pessimistically assume that JS will always write to it. We could, however, try to consider on a per-method basis changing it to a read-only slice!

[bgourlie]

Thanks for the quick reply! Is there a mechanism already in place to special-case on a per-method basis? If not, any thoughts on a good general approach?

[alexcrichton]

Ah unfortunately the method doesn't currently exist at this time

[alexcrichton]

Ok I've spawned this off to #1005 as an actionable item