Wasm closures - value borrowed here after move

help
1

I am trying to render a scene using babylyonjs.
Part of making that work is setting the renderloop on the engine.

I have a wasm_bindgen (not going to share the entire thing) for that function.

#[wasm_bindgen(method, js_name = runRenderLoop, js_class = Engine)]
pub fn run_render_loop(this: &Engine, value: &Closure<dyn FnMut()>);

In rust I have a babylon structure that includes the engine and the scene and all that works fine.
Where I am getting stuck is setting it up so that rust delegate will called.

the code looks like this

let babylon: Babylon = Babylon::new(&canvas);

... a bunch of scene code that executes js (works fine as per chrome debugger)

let cb = Closure::wrap(Box::new(move || {
    babylon.scene.render();
}) as Box<dyn FnMut()>);

babylon.engine.run_render_loop(&cb);

This is where the wheels fall off for me and I don't know how to get past this.

Error: Compiling your crate to WebAssembly failed
33 | let cb = Closure::wrap(Box::new(move || {
| ------- value moved into closure here
34 | babylon.scene.render();
| ------------- variable moved due to use in closure
...
37 | babylon.engine.run_render_loop(&cb);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ value borrowed here after move

Any assistance on getting past this would be greatly appreciated

2

The issue is that the entire Babylon instance gets moved into the closure, when you only want babylon.scene to be moved into it. Try destructuring the top level object first:

(untested)

let Babylon { scene, engine } = babylon;
let cb = Closure::wrap(Box::new(move || {
    scene.render();
}) as Box<dyn FnMut()>);

engine.run_render_loop(&cb);
3

Thank you for the help, much appreciated.
Everything is up and running now, yay!

4

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