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use gapp::{Render, Update};
use glutin::{PossiblyCurrent, WindowedContext};
use instant::Instant;
use std::{thread, time};
use winit::{
    event::{Event, WindowEvent},
    event_loop::{ControlFlow, EventLoop},
};

pub trait WindowInput<C> {
    fn input<'a>(&mut self, event: &WindowEvent<'a>, context: &mut C) -> bool;
}

pub trait Resize {
    fn resize(&mut self, w: u32, h: u32);
}

pub fn run<I: 'static, R: Resize + 'static, T, E: WindowInput<I> + Render<R> + Update + 'static>(
    mut application: E,
    event_loop: EventLoop<T>,
    fps: u64,
    windowed_context: WindowedContext<PossiblyCurrent>,
    mut input_context: I,
    mut renderer: R,
) {
    let timestep = time::Duration::from_nanos(1000000000 / fps);

    let start = Instant::now();
    let mut prev_time = start;

    event_loop.run(move |event, _, control_flow| {
        let window = windowed_context.window();

        *control_flow = ControlFlow::Poll;

        match event {
            Event::WindowEvent { ref event, .. } => {
                match event {
                    WindowEvent::Resized(physical_size) => {
                        windowed_context.resize(*physical_size);
                        renderer.resize(physical_size.width, physical_size.height);
                    }
                    _ => (),
                }
                if application.input(event, &mut input_context) {
                    *control_flow = ControlFlow::Exit;
                }
            }
            Event::RedrawRequested(_) => {
                application.render(&mut renderer);

                windowed_context.swap_buffers().unwrap();
            }
            Event::MainEventsCleared => {
                let frame_duration = prev_time.elapsed();

                application.update(timestep.as_secs_f32());
                if frame_duration < timestep {
                    thread::sleep(timestep - frame_duration);
                }

                window.request_redraw();

                prev_time = Instant::now();
            }
            _ => (),
        }
    });
}