OpenGL in Odin

main.odin

package new 

import gl "vendor:OpenGL"
import "vendor:glfw"

main :: proc() {
    // glfw: initialize and configure
    glfw.Init()
    glfw.WindowHint(glfw.CONTEXT_VERSION_MAJOR, 3)
    glfw.WindowHint(glfw.CONTEXT_VERSION_MINOR, 3)
    glfw.WindowHint(glfw.OPENGL_PROFILE, glfw.OPENGL_CORE_PROFILE)

    // glfw window creation
    window := glfw.CreateWindow(800,600,"OpenGL", nil, nil)
    assert(window != nil, "Failed to create GLFW window")
    glfw.MakeContextCurrent(window)

    // gladLoadGLLoader((GLADloadproc)glfwGetProcAddress)
    gl.load_up_to(3, 3, glfw.gl_set_proc_address)
    gl.Viewport(0, 0, 800,600)

    // build and compile our shader program
    vertexShader := gl.CreateShader(gl.VERTEX_SHADER)
    gl.ShaderSource(vertexShader, 1, &vertexShaderSource, nil)
    fragmentShader := gl.CreateShader(gl.FRAGMENT_SHADER)
    gl.ShaderSource(fragmentShader, 1, &fragmentShaderSource, nil)

    // link shaders
    shaderProgram := gl.CreateProgram()
    gl.AttachShader(shaderProgram, vertexShader)
    gl.AttachShader(shaderProgram, fragmentShader)
    gl.LinkProgram(shaderProgram)

    gl.DeleteShader(vertexShader)
    gl.DeleteShader(fragmentShader)


    // Set up vertex data
    vertices := []f32{
         0.5,  0.5, 0.0,  // top right
         0.5, -0.5, 0.0,  // bottom right
        -0.5, -0.5, 0.0,  // bottom left
        -0.5,  0.5, 0.0,  // top left 
    }

    indicies := []i32 {
        0, 1, 3,
        1, 2, 3,
    }

    VBO, VAO, EBO : u32
    gl.GenVertexArrays(1, &VAO)
    gl.GenBuffers(1, &VBO)
    gl.GenBuffers(1, &EBO)
    gl.BindVertexArray(VAO)

    gl.BindBuffer(gl.ARRAY_BUFFER, VBO)
    gl.BufferData(gl.ARRAY_BUFFER, 12 * size_of(f32), raw_data(vertices), gl.STATIC_DRAW)

    gl.BindBuffer(gl.ELEMENT_ARRAY_BUFFER, EBO)
    gl.BufferData(gl.ELEMENT_ARRAY_BUFFER, 6 * size_of(i32, raw_data(indicies), gl.STATIC_DRAW)

    gl.VertexAttribPointer(0, 3, gl.FLOAT, false, 3 * size_of(f32), 0)
    gl.EnableVertexAttribArray(0)

    gl.BindVertexArray(0)


     // render loop
    for ! glfw.WindowShouldClose(window) {
        processInput(&window)

        gl.ClearColor(0.2, 0.3, 0.3, 1)
        gl.Clear(gl.COLOR_BUFFER_BIT)

        gl.UseProgram(shaderProgram)
        gl.BindVertexArray(VAO)
        gl.DrawElements(gl.TRIANGLES, 6, gl.UNSIGNED_INT, nil)

        glfw.SwapBuffers(window)
        glfw.PollEvents()
    }

    glfw.Terminate()
}

processInput :: proc(window : ^glfw.WindowHandle) {
    if glfw.GetKey(window^, glfw.KEY_ESCAPE) == glfw.PRESS {
        glfw.SetWindowShouldClose(window^, true)
    }
}


vertexShaderSource : cstring = `#version 330 core
layout (location = 0) in vec3 aPos;
void main()
{
   gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);
}
`
fragmentShaderSource: cstring = `#version 330 core
out vec4 FragColor;
void main()
{
    FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0f);
}
`