_2_1_hello_triangle.rs

#![allow(non_upper_case_globals)]
extern crate glfw;
use self::glfw::{Context, Key, Action};

extern crate gl;
use self::gl::types::*;

use std::sync::mpsc::Receiver;
use std::ffi::CString;
use std::ptr;
use std::str;
use std::mem;
use std::os::raw::c_void;

// settings
const SCR_WIDTH: u32 = 800;
const SCR_HEIGHT: u32 = 600;

const vertexShaderSource: &str = r#"
    #version 330 core
    layout (location = 0) in vec3 aPos;
    void main() {
       gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);
    }
"#;

const fragmentShaderSource: &str = r#"
    #version 330 core
    out vec4 FragColor;
    void main() {
       FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0f);
    }
"#;

#[allow(non_snake_case)]
pub fn main_1_2_1() {
    // glfw: initialize and configure
    // ------------------------------
    let mut glfw = glfw::init(glfw::FAIL_ON_ERRORS).unwrap();
    glfw.window_hint(glfw::WindowHint::ContextVersion(3, 3));
    glfw.window_hint(glfw::WindowHint::OpenGlProfile(glfw::OpenGlProfileHint::Core));
    #[cfg(target_os = "macos")]
    glfw.window_hint(glfw::WindowHint::OpenGlForwardCompat(true));

    // glfw window creation
    // --------------------
    let (mut window, events) = glfw.create_window(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", glfw::WindowMode::Windowed)
        .expect("Failed to create GLFW window");

    window.make_current();
    window.set_key_polling(true);
    window.set_framebuffer_size_polling(true);

    // gl: load all OpenGL function pointers
    // ---------------------------------------
    gl::load_with(|symbol| window.get_proc_address(symbol) as *const _);

    let (shaderProgram, VAO) = unsafe {
        // build and compile our shader program
        // ------------------------------------
        // vertex shader
        let vertexShader = gl::CreateShader(gl::VERTEX_SHADER);
        let c_str_vert = CString::new(vertexShaderSource.as_bytes()).unwrap();
        gl::ShaderSource(vertexShader, 1, &c_str_vert.as_ptr(), ptr::null());
        gl::CompileShader(vertexShader);

        // check for shader compile errors
        let mut success = gl::FALSE as GLint;
        let mut infoLog = Vec::with_capacity(512);
        infoLog.set_len(512 - 1); // subtract 1 to skip the trailing null character
        gl::GetShaderiv(vertexShader, gl::COMPILE_STATUS, &mut success);
        if success != gl::TRUE as GLint {
            gl::GetShaderInfoLog(vertexShader, 512, ptr::null_mut(), infoLog.as_mut_ptr() as *mut GLchar);
            println!("ERROR::SHADER::VERTEX::COMPILATION_FAILED\n{}", str::from_utf8(&infoLog).unwrap());
        }

        // fragment shader
        let fragmentShader = gl::CreateShader(gl::FRAGMENT_SHADER);
        let c_str_frag = CString::new(fragmentShaderSource.as_bytes()).unwrap();
        gl::ShaderSource(fragmentShader, 1, &c_str_frag.as_ptr(), ptr::null());
        gl::CompileShader(fragmentShader);
        // check for shader compile errors
        gl::GetShaderiv(fragmentShader, gl::COMPILE_STATUS, &mut success);
        if success != gl::TRUE as GLint {
            gl::GetShaderInfoLog(fragmentShader, 512, ptr::null_mut(), infoLog.as_mut_ptr() as *mut GLchar);
            println!("ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n{}", str::from_utf8(&infoLog).unwrap());
        }

        // link shaders
        let shaderProgram = gl::CreateProgram();
        gl::AttachShader(shaderProgram, vertexShader);
        gl::AttachShader(shaderProgram, fragmentShader);
        gl::LinkProgram(shaderProgram);
        // check for linking errors
        gl::GetProgramiv(shaderProgram, gl::LINK_STATUS, &mut success);
        if success != gl::TRUE as GLint {
            gl::GetProgramInfoLog(shaderProgram, 512, ptr::null_mut(), infoLog.as_mut_ptr() as *mut GLchar);
            println!("ERROR::SHADER::PROGRAM::COMPILATION_FAILED\n{}", str::from_utf8(&infoLog).unwrap());
        }
        gl::DeleteShader(vertexShader);
        gl::DeleteShader(fragmentShader);

        // set up vertex data (and buffer(s)) and configure vertex attributes
        // ------------------------------------------------------------------
        // HINT: type annotation is crucial since default for float literals is f64
        let vertices: [f32; 9] = [
            -0.5, -0.5, 0.0, // left
             0.5, -0.5, 0.0, // right
             0.0,  0.5, 0.0  // top
        ];
        let (mut VBO, mut VAO) = (0, 0);
        gl::GenVertexArrays(1, &mut VAO);
        gl::GenBuffers(1, &mut VBO);
        // bind the Vertex Array Object first, then bind and set vertex buffer(s), and then configure vertex attributes(s).
        gl::BindVertexArray(VAO);

        gl::BindBuffer(gl::ARRAY_BUFFER, VBO);
        gl::BufferData(gl::ARRAY_BUFFER,
                       (vertices.len() * mem::size_of::<GLfloat>()) as GLsizeiptr,
                       &vertices[0] as *const f32 as *const c_void,
                       gl::STATIC_DRAW);

        gl::VertexAttribPointer(0, 3, gl::FLOAT, gl::FALSE, 3 * mem::size_of::<GLfloat>() as GLsizei, ptr::null());
        gl::EnableVertexAttribArray(0);

        // note that this is allowed, the call to gl::VertexAttribPointer registered VBO as the vertex attribute's bound vertex buffer object so afterwards we can safely unbind
        gl::BindBuffer(gl::ARRAY_BUFFER, 0);

        // You can unbind the VAO afterwards so other VAO calls won't accidentally modify this VAO, but this rarely happens. Modifying other
        // VAOs requires a call to glBindVertexArray anyways so we generally don't unbind VAOs (nor VBOs) when it's not directly necessary.
        gl::BindVertexArray(0);

        // uncomment this call to draw in wireframe polygons.
        // gl::PolygonMode(gl::FRONT_AND_BACK, gl::LINE);

        (shaderProgram, VAO)
    };

    // render loop
    // -----------
    while !window.should_close() {
        // events
        // -----
        process_events(&mut window, &events);

        // render
        // ------
        unsafe {
            gl::ClearColor(0.2, 0.3, 0.3, 1.0);
            gl::Clear(gl::COLOR_BUFFER_BIT);

            // draw our first triangle
            gl::UseProgram(shaderProgram);
            gl::BindVertexArray(VAO); // seeing as we only have a single VAO there's no need to bind it every time, but we'll do so to keep things a bit more organized
            gl::DrawArrays(gl::TRIANGLES, 0, 3);
            // glBindVertexArray(0); // no need to unbind it every time
        }

        // glfw: swap buffers and poll IO events (keys pressed/released, mouse moved etc.)
        // -------------------------------------------------------------------------------
        window.swap_buffers();
        glfw.poll_events();
    }
}

// NOTE: not the same version as in common.rs!
fn process_events(window: &mut glfw::Window, events: &Receiver<(f64, glfw::WindowEvent)>) {
    for (_, event) in glfw::flush_messages(events) {
        match event {
            glfw::WindowEvent::FramebufferSize(width, height) => {
                // make sure the viewport matches the new window dimensions; note that width and
                // height will be significantly larger than specified on retina displays.
                unsafe { gl::Viewport(0, 0, width, height) }
            }
            glfw::WindowEvent::Key(Key::Escape, _, Action::Press, _) => window.set_should_close(true),
            _ => {}
        }
    }
}