GLFW Simple tutorial demo

README.md

GLFW Simple tutorial demo

https://www.glfw.org/docs/latest/quick.html

simple.c

#include <glad/gl.h>
#define GLFW_INCLUDE_NONE
#include <GLFW/glfw3.h>


#include "linmath.h"


#include <stdlib.h>
#include <stdio.h>


static const struct
{
  float x, y;
  float r, g, b;
} vertices[3] =
{
  {-0.6f, -0.4f, 1.f, 0.f, 0.f},
  { 0.6f, -0.4f, 0.f, 1.f, 0.f},
  {  0.f,  0.6f, 0.f, 0.f, 1.f}
};
 
 
static const char *
vertex_shader_text =
"#version 110\n"
"uniform mat4 MVP;\n"
"attribute vec3 vCol;\n"
"attribute vec2 vPos;\n"
"varying vec3 color;\n"
"void main()\n"
"{\n"
"    gl_Position = MVP * vec4(vPos, 0.0, 1.0);\n"
"    color = vCol;\n"
"}\n";

 
static const char *
fragment_shader_text =
"#version 110\n"
"varying vec3 color;\n"
"void main()\n"
"{\n"
"    gl_FragColor = vec4(color, 1.0);\n"
"}\n";


static void
error_callback (int error, const char* description)
{
  fprintf(stderr, "Error: %s\n", description);
}


static void
key_callback (GLFWwindow* window, int key, int scancode, int action, int mods)
{
  if (key == GLFW_KEY_ESCAPE && action == GLFW_PRESS)
    glfwSetWindowShouldClose(window, GLFW_TRUE);
}


int
main (void)
{
  GLFWwindow* window;
  GLuint vertex_buffer;
  GLuint vertex_shader;
  GLuint fragment_shader;
  GLuint program;
  GLint mvp_location;
  GLint vpos_location;
  GLint vcol_location;
 
  glfwSetErrorCallback (error_callback);

  if (!glfwInit ())
    exit (EXIT_FAILURE);

  glfwWindowHint (GLFW_CONTEXT_VERSION_MAJOR, 2);
  glfwWindowHint (GLFW_CONTEXT_VERSION_MINOR, 0);

  window = glfwCreateWindow (640, 480, "Simple example", NULL, NULL);
  if (!window)
  {
    glfwTerminate ();
    exit (EXIT_FAILURE);
  }

  glfwSetKeyCallback (window, key_callback);

  glfwMakeContextCurrent (window);
  gladLoadGL (glfwGetProcAddress);
  glfwSwapInterval (1);

  /* NOTE: OpenGL error checks have been omitted for brevity. */

  glGenBuffers (1, &vertex_buffer);
  glBindBuffer (GL_ARRAY_BUFFER, vertex_buffer);
  glBufferData (GL_ARRAY_BUFFER, sizeof (vertices), vertices, GL_STATIC_DRAW);

  vertex_shader = glCreateShader (GL_VERTEX_SHADER);
  glShaderSource (vertex_shader, 1, &vertex_shader_text, NULL);
  glCompileShader (vertex_shader);

  fragment_shader = glCreateShader (GL_FRAGMENT_SHADER);
  glShaderSource (fragment_shader, 1, &fragment_shader_text, NULL);
  glCompileShader (fragment_shader);

  program = glCreateProgram ();
  glAttachShader (program, vertex_shader);
  glAttachShader (program, fragment_shader);
  glLinkProgram (program);

  mvp_location = glGetUniformLocation (program, "MVP");
  vpos_location = glGetAttribLocation (program, "vPos");
  vcol_location = glGetAttribLocation (program, "vCol");

  glEnableVertexAttribArray (vpos_location);
  glVertexAttribPointer (vpos_location, 2, GL_FLOAT, GL_FALSE, sizeof (vertices[0]), (void*) 0);
  glEnableVertexAttribArray (vcol_location);
  glVertexAttribPointer (vcol_location, 3, GL_FLOAT, GL_FALSE, sizeof (vertices[0]), (void*) (sizeof (float) * 2));

  while (!glfwWindowShouldClose (window))
  {
    float ratio;
    int width;
    int height;
    mat4x4 m;
    mat4x4 p;
    mat4x4 mvp;

    glfwGetFramebufferSize (window, &width, &height);
    ratio = width / (float) height;

    glViewport (0, 0, width, height);
    glClear (GL_COLOR_BUFFER_BIT);

    mat4x4_identity (m);
    mat4x4_rotate_Z (m, m, (float) glfwGetTime ());
    mat4x4_ortho (p, -ratio, ratio, -1.f, 1.f, 1.f, -1.f);
    mat4x4_mul (mvp, p, m);

    glUseProgram (program);
    glUniformMatrix4fv (mvp_location, 1, GL_FALSE, (const GLfloat*) mvp);
    glDrawArrays (GL_TRIANGLES, 0, 3);

    glfwSwapBuffers (window);
    glfwPollEvents ();
  }

  glfwDestroyWindow (window);

  glfwTerminate ();
  exit (EXIT_SUCCESS);
}