Post History

Nannou model requires a function poniter: How to return a function pointer

Trying to make a [nannou app](https://nannou.cc/) from the [template](https://github.com/nannou-org/nannou/blob/master/examples/templates/template_app.rs) but with a customizable  `model()` function.

The template has this `main()`:
 
    fn main() {
         nannou::app(model).update(update).run();
    }

The `model` that goes intot the `app()` is a function that returns a `Model`. My `Model` struct is very simple: 

    struct Model {
        color: Hsl,
        max_time: u32,
        counter: u32,
    }


The `model` function simply returns a `Model` struct. But instead of hard coding the parameters in a `model()` function I want a `model_function_creator()` that takes `max_time`and a `color_tuple`, *captures* them and returns a `model` function that is parameterized. 

I tried something like this:

    fn model_function_creator(max_time: u32, color_tuple: (f32, f32, f32)) -> fn(&App) -> Model {
        Box::new(move |_app: &App| Model {
            color: hsl(color.0, color.1, color.2),
            max_time: max_time,
            counter: 0,
        })
    }

So that in `main()`, I can call the `model_function_creator` with custom parameters like this: 

    fn main() {
        let max_time = 100;
        let color = (0.3, 0.5, 0.5);

        nannou::app(model_function_creator(max_time, color))
            .update(update)
            .simple_window(view)
            .run();
    }


But I get the following error messages:
    
    expected `for<'r> fn(&'r nannou::App) -> Model` because of return type
and 

    expected fn pointer, found struct `Box`

How do I return a `fn pointer` from a function and still have it *capture* the two parameter I pass to it.