// Copyright 2015 Brendan Zabarauskas and the gl-rs developers
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

extern crate gl;
extern crate glutin;

fn main() {
    let mut events_loop = glutin::EventsLoop::new();
    let window = glutin::WindowBuilder::new();
    let gl_window = glutin::ContextBuilder::new()
        .build_windowed(window, &events_loop)
        .unwrap();

    // It is essential to make the context current before calling `gl::load_with`.
    let gl_window = unsafe { gl_window.make_current().unwrap() };

    // Load the OpenGL function pointers
    // TODO: `as *const _` will not be needed once glutin is updated to the latest gl version
    gl::load_with(|symbol| gl_window.get_proc_address(symbol) as *const _);

    events_loop.run_forever(|event| {
        use glutin::{ControlFlow, Event, WindowEvent};

        if let Event::WindowEvent { event, .. } = event {
            if let WindowEvent::CloseRequested = event {
                return ControlFlow::Break;
            }
        }

        unsafe {
            gl::ClearColor(0.3, 0.3, 0.3, 1.0);
            gl::Clear(gl::COLOR_BUFFER_BIT);
        }

        gl_window.swap_buffers().unwrap();

        ControlFlow::Continue
    });
}