ShaderTool/src/renderer.c

#include <FreeImage.h>
#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <stdlib.h>
#include <time.h>

#include "log.h"
#include "renderer.h"
#include "shaders.h"

#define UNUSED(a) (void)a

/**
 * @brief Initialize GLFW and OpenGL, and create a window.
 *
 * @param width The width of the window to create.
 * @param height The height of the window to create.
 * @return A pointer to the newly created GLFW window, or `NULL` on error.
 */
GLFWwindow *initialize_window(int width, int height) {
  /* Initialize GLFW */
  if (!glfwInit()) {
    log_error("[GLFW] Failed to init");
    return NULL;
  }
  glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
  glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
  glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

  /* Create window */
  GLFWwindow *window =
      glfwCreateWindow(width, height, "ShaderTool", NULL, NULL);
  if (window == NULL) {
    log_error("[GLFW] Failed to create window");
    glfwTerminate();
    return NULL;
  }
  glfwMakeContextCurrent(window);
  log_debug("[GLFW] Created window of size %d, %d", width, height);

  glViewport(0, 0, width, height);
  glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);

  /* Initialize OpenGL */
  if (glewInit() != GLEW_OK) {
    log_error("[GLEW] Failed to initialize");
    return NULL;
  }
  log_debug("[GLEW] Initialized successfully");

  return window;
}

/**
 * @brief Initialize the vertex array.
 *
 * This functions defines a simple rectangle containing the whole
 * viewport.
 *
 * @return The vertex array object ID.
 */
unsigned int initialize_vertices() {
  /* Define vertices */
  float vertices[] = {
      // positions     // texture coords
      1.0,  1.0,  0.0, 1.0, 1.0, // top right
      1.0,  -1.0, 0.0, 1.0, 0.0, // bottom right
      -1.0, -1.0, 0.0, 0.0, 0.0, // bottom left
      -1.0, 1.0,  0.0, 0.0, 1.0, // top left
  };
  unsigned int indices[] = {
      0, 1, 3, // first triangle
      1, 2, 3  // second triangle
  };

  unsigned int VBO = 0;
  glGenBuffers(1, &VBO);
  unsigned int EBO = 0;
  glGenBuffers(1, &EBO);
  unsigned int VAO = 0;
  glGenVertexArrays(1, &VAO);

  glBindVertexArray(VAO);
  glBindBuffer(GL_ARRAY_BUFFER, VBO);
  glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
  glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
  glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices,
               GL_STATIC_DRAW);

  /* position attribute */
  glEnableVertexAttribArray(0);
  glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void *)0);
  /* texture coord attribute */
  glEnableVertexAttribArray(1);
  glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(float),
                        (void *)(3 * sizeof(float)));

  log_debug("Vertex data initialized successfully");

  return VAO;
}

/**
 * @brief Callback to adjust the size of the viewport when the window
 * is resized.
 *
 * @param window The current window.
 * @param width The new width.
 * @param height The new height.
 */
void framebuffer_size_callback(GLFWwindow *window, int width, int height) {
  UNUSED(window);
  glViewport(0, 0, width, height);
}

/**
 * @brief Captures a screenshot of the current window.
 *
 * Takes the dimensions of the viewport to save a pixel array of the
 * same dimensions. Uses FreeImage to create an image from the raw
 * pixels and save it to disk.
 */
void capture_screenshot() {
  time_t now = time(NULL);
  struct tm *timenow = gmtime(&now);
  char image_filename[255] = {0};
  strftime(image_filename, sizeof(image_filename),
           "shadertool_%Y%m%d_%H%M%S.png", timenow);

  int viewport[4] = {0};
  glGetIntegerv(GL_VIEWPORT, viewport);

  GLubyte *pixels = calloc(3 * viewport[2] * viewport[3], 1);
  glReadPixels(0, 0, viewport[2], viewport[3], GL_BGR, GL_UNSIGNED_BYTE,
               pixels);

  FIBITMAP *image = FreeImage_ConvertFromRawBits(
      pixels, viewport[2], viewport[3], 3 * viewport[2], 24, FI_RGBA_RED_MASK,
      FI_RGBA_GREEN_MASK, FI_RGBA_BLUE_MASK, false);

  if (FreeImage_Save(FIF_PNG, image, image_filename, 0)) {
    log_debug("Image saved to %s", image_filename);
  } else {
    log_error("Failed to saved image to %s", image_filename);
  }

  FreeImage_Unload(image);
  free(pixels);
}

/**
 * @brief Ensure the window is closed when the user presses the escape
 * key.
 *
 * @param window The current window.
 * @param shader_program Pointer to the shader program to update if needed.
 * @param fragment_shader_file The shader file to reload if needed.
 */
void process_input(GLFWwindow *window, unsigned int *screen_shader,
                   const char *const screen_shader_file,
                   unsigned int *buffer_shader,
                   const char *const buffer_shader_file) {
  if (glfwGetKey(window, GLFW_KEY_ESCAPE) == GLFW_PRESS) {
    log_debug("Quitting");
    glfwSetWindowShouldClose(window, true);
  } else if (glfwGetKey(window, GLFW_KEY_R) == GLFW_PRESS) {
    compile_shaders(screen_shader, screen_shader_file);
    if (buffer_shader_file) {
      compile_shaders(buffer_shader, buffer_shader_file);
    }
  } else if (glfwGetKey(window, GLFW_KEY_S) == GLFW_PRESS) {
    capture_screenshot();
  }
}