[rstream-graph] optional streams on stream sync ?

[ruigil]

I've been playing with rstream-graph, and I've come across what I think is a valid use case that is not supported in stream sync.

After the first sync, stream sync triggers the function when ANY of the input streams produces a value or ALL of them produces a value. My use case requires that I can define a subset of the inputs that can trigger the function.

In the following node, I want to trigger the renderFrame function once for every previous node execution, but the mouse stream triggers the function leading to overdrawing issues, and I can't use the flag reset=true of stream sync, because the input texture is only produced once.

{
    fn: renderFrame,
    ins:{
        buffer: { stream: "/previous/node" },
        texture: { path: "/data/created/once" },
        mouse: { stream: () => gestures }
    }
}

I need to be able to specify a subset of the inputs that will NOT trigger the function after the first sync while keeping the latest value, (in this case ['texture','mouse'] ), also with the reset flag applied only to the remaining inputs.

Do you think this is a valid use case, or rstream-graph is meant to be used in "pure" dataflows only, with functions without side-effects? If you think this is valid, what would be the best way to implement this feature?

I tried to change StreamSync and the PartitionSync transducer to accept a new parameter of optional stream ids, but I imagine it could be specified as a flag in the input itself, i.e.

{
    fn: renderFrame,
    ins:{
        buffer: { stream: "/previous/node" },
        texture: { path: "/data/created/once" , optional: true },
        mouse: { stream: () => gestures , optional: true }
    }
}

[postspectacular]

Hi @ruigil - that's an interesting thought experiment which will also require some experimentation from my side. Will get back to you in the next couple of days...