pub trait Window {
fn done(&self) -> bool;
fn render_frame(
&mut self,
func: &mut dyn FnMut(&mut RenderBuffer, &mut Cheval),
cheval: &mut Cheval
);
fn next_frame(&mut self);
fn get_key(&mut self) -> Option<u32>;
fn restore_positions(&mut self, _filename: &str) { ... }
fn store_positions(&mut self, _filename: &str) { ... }
}