chinedufn

There's a recent issue [1] in the wasm-bindgen repo that explains this, but essentially:

- In this demo the WebGLRenderingContext was created on the Rust side (technically by calling a light JS shim), but it could've just as well have been passed in from JS.

- This means that JS could very easily have had access to the WebGLRenderingContext.

- This means that we cannot guarantee that it is immutable. Who is to say that there isn't a line of JS `gl.mutated! = true;` that we don't know about? We have no guarantees that whoever instantiated this WebAssembly module isn't doing something funky.

- So we treat most DOM / JS APIs as if they have interior mutability, so more or less you can think of them as `RefCell`'s [2]

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As an aside. When you work with WebGL you're just making calls to the GPU and your state on the GPU gets mutated. The object just controls state (WebGlRenderingContext) does not get mutated (aside from maybe a couple things that I'm forgetting..?).

As in.. `gl.viewport` doesn't actually mutate `gl`. But again.. just a small aside!

In general the idea here is that we can't guarantee that there is only one mutable reference so there is no point in calling these things `&mut`, even for things that really do mutate.

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So yup! Interior mutability without runtime checks for many of the APIs is "the right way" in today's idiomatic Rust + WASM + DOM access since you can't guarantee that there isn't foul play going on from whoever instantiated the module.

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Does this cause issues? It hasn't (noticeably) for me yet but I'm only a couple months into using `web_sys` so I haven't worked with every single DOM API.. so grain of salt!

One thing that can be done is playing around with the numbers / uniforms in the fragment shader to change the look. For many use cases you can get pretty far with that without actually changing the implementation in this demo.

If a more physically based level of realism is needed (like the water ripples on click in the demo that you linked) you can use techniques like height simulation based on a wave equation [1].

You'll of course need to balance realism with realtime feasibility - but often times getting a much better look comes down to tweaking some numbers until things look good!