glsl-basic/src/graphics.cpp

#include <boost/algorithm/string.hpp>
#include <boost/algorithm/string/case_conv.hpp>
#include <boost/log/trivial.hpp>
#include <exception>
#include <glad/glad.c>
// glad must be loaded before GLFW
#include "graphics.hpp"
#include "main.hpp"

#include <iostream>

using namespace std;

ShaderProgram::Base ShaderProgram::baseFromName(string name) {
  string lname = name;
  boost::algorithm::to_lower(lname); // yes, cpp needs a library to do this.
                                     // luckily I'm already using boost so I
                                     // don't need to worry too much about it.
  // can't do a switch over strings in cpp.
  if (lname == "empty") {
    return Empty;
  }
  if (lname == "triangle") {
    return Triangle;
  } else {
    BOOST_LOG_TRIVIAL(fatal) << "unknown base program \"" << name << "\"";
    exit(EXIT_USAGE);
  }
}

/* class ShaderProgram Implementations */
string ShaderProgram::baseName() {
  /*
  BOOST_LOG_TRIVIAL(debug) << "this->base: " << this->base
                           << " Base::Empty: " << Base::Empty
                           << " Base::Triangle: " << Base::Triangle;
  */
  switch (this->base) {
  case ShaderProgram::Base::Empty:
    return "Empty";
  case ShaderProgram::Base::Triangle:
    return "Triangle";
  default:
    // this should never occur, as the switch case should cover all variants.
    throw std::runtime_error("Undefined base Program");
  }
}

/**
 * @param vertexSource C style string with NULL termination
 * @param fragSource C style string with NULL termination
 */
ShaderProgram::ShaderProgram(Base base, string vertexSource,
                             string fragSource) {
  int success;
  char infoLog[512];
  const char* vertexSource_c = vertexSource.c_str();
  const char* fragSource_c = fragSource.c_str();
  this->base = base;
  BOOST_LOG_TRIVIAL(info) << "With base program \"" << this->baseName() << "\"";
  // NOTE: char arrays and char pointers are not actually the same.
  // glShaderSource requires a char[] as it appears. We pass the
  // variable by reference to avoid duplication in memory.
  BOOST_LOG_TRIVIAL(trace) << "creating empty shaders";
  this->vertex = glCreateShader(GL_VERTEX_SHADER);
  this->frag = glCreateShader(GL_FRAGMENT_SHADER);

  BOOST_LOG_TRIVIAL(trace) << "loading vertex shader";
  glShaderSource(this->vertex, 1, &vertexSource_c, NULL);
  BOOST_LOG_TRIVIAL(trace) << "compiling vertex shader";
  glCompileShader(this->vertex);
  // check if it worked
  glGetShaderiv(this->vertex, GL_COMPILE_STATUS, &success);
  if (!success) {
    glGetShaderInfoLog(this->vertex, 512, NULL, infoLog);
    BOOST_LOG_TRIVIAL(fatal) << "could not compile vertex shader:\n\n"
                             << infoLog << std::endl;
    exit(EXIT_SHADER);
  }

  /* FIXME: Optionally include a frag shader
  BOOST_LOG_TRIVIAL(trace) << "loading fragments shader";
  glShaderSource(this->frag, 1, &fragSource_c, NULL);
  BOOST_LOG_TRIVIAL(trace) << "compiling fragments shader";
  glCompileShader(this->frag);
  // check if it worked
  glGetShaderiv(this->frag, GL_COMPILE_STATUS, &success);
  if (!success) {
    glGetShaderInfoLog(this->frag, 512, NULL, infoLog);
    BOOST_LOG_TRIVIAL(fatal) << "could not compile fragments shader:\n\n"
                             << infoLog << std::endl;
    exit(EXIT_SHADER);
  }
  */
}

/** defines the base program behavior.
 *
 * will be called in `mainWindow`.
 */
int ShaderProgram::run(GLFWwindow *window) {
  if (this->base == Triangle) {
    float vTriangle[] = {
        -0.5f, -0.5f, 0.0f, // opengl
        0.5f,  -0.5f, 0.0f, // treats 3d arrays
        0.0f,  0.5f,  0.0f  // as large 1d arrays
    };
    unsigned int oTriangle;
    glGenBuffers(1, &oTriangle);
    glBindBuffer(GL_ARRAY_BUFFER, oTriangle);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vTriangle), vTriangle, GL_STATIC_DRAW);
    while (!glfwWindowShouldClose(window)) {
      processInput(window);

      glClearColor(0.9f, 0.3f, 0.3f, 1.0f);
      glClear(GL_COLOR_BUFFER_BIT);

      glfwSwapBuffers(window);
      glfwPollEvents();
    }
    return 0;
  } else // Empty
  {

    return 0;
    while (!glfwWindowShouldClose(window)) {
      processInput(window);

      glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
      glClear(GL_COLOR_BUFFER_BIT);

      glfwSwapBuffers(window);
      glfwPollEvents();
    }
    return 0;
  }
}

/* functions that run out graphics stuff */

void framebuffer_size_callback(GLFWwindow *window, int width, int height) {
  glViewport(0, 0, width, height);
}

GLFWwindow *initGl() {
  /* graphics stuff */
  glfwInit();
  glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
  glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
  glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
  // glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);

  GLFWwindow *window = glfwCreateWindow(800, 600, "Shader Loader", NULL, NULL);
  if (window == NULL) {
    printf("Failed to create GLFW window\n");
    glfwTerminate();
    exit(EXIT_GL);
  }
  glfwMakeContextCurrent(window);

  if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress)) {
    printf("Failed to initialize GLAD\n");
    exit(EXIT_GL);
  }

  glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
  return window;
}

int mainWindow(ShaderProgram *shaderProgram, GLFWwindow *window) {

  int result = 0;

  BOOST_LOG_TRIVIAL(trace) << "Base program";
  result = shaderProgram->run(window);
  BOOST_LOG_TRIVIAL(trace) << "Left base program";

  glfwTerminate();
  return result;
}

void processInput(GLFWwindow *window) {
  if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS)
    glfwSetWindowShouldClose(window, true);
}