uniform parameters

#include <stdio.h>
#include <stdlib.h>
#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <glm/glm.hpp>

using namespace glm;

#include "../common/shader.hpp"

GLFWwindow* window;

int main(void) {
  // Initialise GLFW
  if (!glfwInit()) {
    fprintf(stderr, "Failed to initialize GLFW\n");
    getchar();
    return -1;
  }

  glfwWindowHint(GLFW_SAMPLES, 4);
  glfwWindowHint(GLFW_RESIZABLE, GL_FALSE);
  glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
  glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
  glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE); // To make MacOS happy; should not be needed
  glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

  // Open a window and create its OpenGL context
  window = glfwCreateWindow(1024, 768, "Playground", nullptr, nullptr);
  if (window == nullptr) {
    fprintf(stderr, "Failed to open GLFW window. If you have an Intel GPU, they are not 3.3 compatible. Try the 2.1 version of the tutorials.\n");
    getchar();
    glfwTerminate();
    return -1;
  }
  glfwMakeContextCurrent(window);

  // Initialize GLEW
  // IMPORTANT: if this is not enable this might create SegmentationFault
  glewExperimental = true; // For core profile
  if (glewInit() != GLEW_OK) {
    fprintf(stderr, "Failed to initialize GLEW\n");
    getchar();
    glfwTerminate();
    return -1;
  }

  // Ensure we can capture the escape key being pressed below
  glfwSetInputMode(window, GLFW_STICKY_KEYS, GL_TRUE);

  // GL code starts

  // Dark blue background
  glClearColor(0.0f, 0.0f, 0.4f, 0.0f);

  GLuint vao;
  glGenVertexArrays(1, &vao);
  glBindVertexArray(vao);

  GLuint programID = LoadShaders("shader.vert", "shader.frag");

  static const GLfloat vertices[] = {
      -0.5f, -0.5f, 0.0f,
      0.5f, -0.5f, 0.0f,
      0.0f, 0.5f, 0.0f,
  };

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

  int colorLoc = glGetUniformLocation(programID, "color");

  do {
    glClear(GL_COLOR_BUFFER_BIT);

    glUseProgram(programID);
    float time = glfwGetTime();
    float color = sin(time) * 0.2f;
    glUniform4f(colorLoc, color, color + 0.5f, color, 1.0f);

    glEnableVertexAttribArray(0);
    glBindBuffer(GL_ARRAY_BUFFER, vbo);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, nullptr);
    glDrawArrays(GL_TRIANGLES, 0, 3);
    glDisableVertexAttribArray(0);

    // Swap buffers
    glfwSwapBuffers(window);
    glfwPollEvents();

  } while (glfwGetKey(window, GLFW_KEY_ESCAPE) != GLFW_PRESS &&
    glfwWindowShouldClose(window) == 0);

  glDeleteBuffers(1, & vbo);
  glDeleteVertexArrays(1, & vao);
  glDeleteProgram(programID);

  // GL code ends

  // Close OpenGL window and terminate GLFW
  glfwTerminate();

  return 0;
}