pub type WindowResizeFn = fn (window &Window, w int, h int)

@[heap]
pub struct Window {
    id string = '_window_'
pub mut:
    resize_fn WindowResizeFn = unsafe { nil }
}

@[params]
pub struct WindowParams {
pub:
    on_resize WindowResizeFn = unsafe { nil }
}

fn window_resized(mut w &Window) {
    window_width, window_height := 200, 100

    if w.resize_fn != unsafe { WindowResizeFn(0) } {
        println('fn present ${window_width} ${window_height}')
        w.resize_fn(w, window_width, window_height)
    }
}

fn on_event(mut w Window) {
    window_resized(mut w)
}

fn on_resize(window &Window, w int, h int) {
    println(' ${w} ${h}')
}

fn main() {
    mut w := &Window{
        resize_fn: on_resize
    }
    on_event(mut w)
}