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use std::cell::RefCell;
use std::rc::Rc;
use log::error;
use wasm_bindgen::prelude::*;
/// use `window.requestAnimationFrame()` to schedule calling a
/// function as long as the function returns true.
pub struct RenderLoop {
inner: Rc<RefCell<Closure<dyn FnMut(f64)>>>,
}
impl RenderLoop {
fn request_animation_frame(f: &Closure<dyn FnMut(f64)>) -> Result<(), JsValue> {
web_sys::window()
.ok_or("no window")?
.request_animation_frame(f.as_ref().unchecked_ref())?;
Ok(())
}
/// `fun` takes a timestamp in the same space as the document
/// timeline and returns a flag specifying whether we should
/// schedule another frame..
pub fn new<T: FnMut(f64) -> bool + 'static>(mut fun: T) -> Self {
// use stub closure so we don't need an `Option` to flag
// whether the `RefCell` is filled or not, and otherwise we'd
// need to use `MaybeUninit` and `unsafe`.
let inner = Rc::new(RefCell::new(Closure::new(|_| {})));
let rloop = inner.clone();
*inner.borrow_mut() = Closure::new(move |t| {
if fun(t) {
if let Err(e) = Self::request_animation_frame(&rloop.borrow()) {
error!("couldn't request animation frame: {:?}", e);
}
}
});
Self { inner }
}
/// start animating.
pub fn start(&self) -> Result<(), JsValue> {
Self::request_animation_frame(&self.inner.borrow())?;
Ok(())
}
}
impl Clone for RenderLoop {
fn clone(&self) -> Self {
Self {
inner: self.inner.clone(),
}
}
}
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