engine.cpp

#include <GLAD\glad.h>
#include <GLFW\glfw3.h>
#include "WindowInit.hpp"
#include <iostream>

const char* vertexShaderSource = "#version 330 core\n"
"layout (location = 0) in vec3 aPos;\n"
"void main()\n"
"{\n"
"   gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);\n"
"}\0";
const char* fragmentShaderSource = "#version 330 core\n"
"out vec4 FragColor;\n"
"void main()\n"
"{\n"
"   FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0f);\n"
"}\n\0";

// Resolution Constants
const unsigned int SCR_WIDTH = 800;
const unsigned int SCR_HEIGHT = 600;

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

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

unsigned int init_vertex_shader() {
	
	int success;
	char infoLog[512];

	// vertex shader
	unsigned int vertexShader = glCreateShader(GL_VERTEX_SHADER);
	glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
	glCompileShader(vertexShader);
	
	// check for shader compile errors
	glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);
	if (!success)
	{
		glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
		std::cout << "ERROR::SHADER::VERTEX::COMPILATION_FAILED\n" << infoLog << std::endl;
	}

	return vertexShader;
}

unsigned int init_fragment_shader() {

	int success;
	char infoLog[512];

	// fragment shader
	unsigned int fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
	glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
	glCompileShader(fragmentShader);
	// check for shader compile errors
	glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);
	if (!success)
	{
		glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
		std::cout << "ERROR::SHADER::FRAGMENT::COMPILATION_FAILED\n" << infoLog << std::endl;
	}

	return fragmentShader;
}

unsigned int link_shaders(unsigned int vertexShader, unsigned int fragmentShader) {
	
	int success;
	char infoLog[512];
	
	unsigned int shaderProgram = glCreateProgram();
	glAttachShader(shaderProgram, vertexShader);
	glAttachShader(shaderProgram, fragmentShader);
	glLinkProgram(shaderProgram);
	// check for linking errors
	glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);
	if (!success) {
		glGetProgramInfoLog(shaderProgram, 512, NULL, infoLog);
		std::cout << "ERROR::SHADER::PROGRAM::LINKING_FAILED\n" << infoLog << std::endl;
	}
	glDeleteShader(vertexShader);
	glDeleteShader(fragmentShader);

	return shaderProgram;
}

int main() {

	glfwInit();

	GLFWwindow* window = init_window(SCR_WIDTH, SCR_HEIGHT);

	if (window == nullptr) { // Using nullptr over NULL for type safety
		std::cout << "Failed to create GLFW window." << std::endl;
		glfwTerminate();
		return -1;
	}

	glfwMakeContextCurrent(window);
	                                                                                 
	if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress)) {
		std::cout << "Failed to init GLAD." << std::endl;
		return -1;
	}

	unsigned int vertexShader = init_vertex_shader();
	unsigned int fragmentShader = init_fragment_shader();
	unsigned int shaderProgram = link_shaders(vertexShader, fragmentShader);

	glViewport(0, 0, 800, 600); // Where to open window x, y then resolution

	glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);

	float vertices[] = {
		-0.5f, -0.5f, 0.0f, //left
		 0.5,  -0.5f, 0.0f, // right
		 0.0f,  0.5f, 0.0f //top
	};

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

	// bind the Vertex Array Object first, then bind and set vertex buffer(s), and then configure vertex attributes(s).
	glBindVertexArray(VAO);

	glBindBuffer(GL_ARRAY_BUFFER, VBO);
	glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
	glEnableVertexAttribArray(0);

	// note that this is allowed, the call to glVertexAttribPointer registered VBO as the vertex attribute's bound vertex buffer object so afterwards we can safely unbind
	glBindBuffer(GL_ARRAY_BUFFER, 0);

	// You can unbind the VAO afterwards so other VAO calls won't accidentally modify this VAO, but this rarely happens. Modifying other
	// VAOs requires a call to glBindVertexArray anyways so we generally don't unbind VAOs (nor VBOs) when it's not directly necessary.
	glBindVertexArray(0);


	// uncomment this call to draw in wireframe polygons.
	//glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);

	// Render Loop
	while (!glfwWindowShouldClose(window)) {
		
		// Check for Input
		processInput(window);

		// Render
		glClearColor(0.6f, 0.2f, 0.2f, 1.0f);
		glClear(GL_COLOR_BUFFER_BIT);

		// draw our first triangle
		glUseProgram(shaderProgram);
		glBindVertexArray(VAO); // seeing as we only have a single VAO there's no need to bind it every time, but we'll do so to keep things a bit more organized
		glDrawArrays(GL_TRIANGLES, 0, 3);
		// glBindVertexArray(0); // no need to unbind it every time 

		// Check and Call Events + Swap Bufffer (See Double Buffering)
		glfwSwapBuffers(window);
		glfwPollEvents();
	}

	// Time to free resources
	glDeleteVertexArrays(1, &VAO);
	glDeleteBuffers(1, &VBO);
	glDeleteProgram(shaderProgram);
	glfwTerminate();
	return 0;

}