OpenGL Tutorial 1 (QS) – Hello GLFW Window

Getting started by displaying a graphics window is the 1st step towards creating your new OpenGL game or application. The window we’re creating literally just cycles through displaying different colours, but it still takes significant effort to get to that stage.

GLFW is the library that we’ll be using to create our OpenGL display window. The window itself encapsulates an OpenGL context, i.e. the API’s brains – residing and working for us under the hood. GLFW also includes numerous features, including polled and event driven user input: keyboard, mouse and joystick control; windowed and fullscreen modes, and more.

This tutorial demonstrates step by step... how to download and set up GLFW to be used with Visual Studio 2022 Community Edition. Details include configuring the OpenGL glad loading library, adding and compiling source code files, configuring project settings, and enabling the GLSL shading language extension.

Source code: C++ from... main.cpp

#include <glad/glad.h> // GLAD: https://github.com/Dav1dde/glad ... GLAD 2 also works via the web-service: https://gen.glad.sh/ (leaving all checkbox options unchecked)
#include <GLFW/glfw3.h>
 
#include <iostream> 
 
int main()
{	
	// (1) GLFW: Initialise & Configure
	// -----------------------------------------
	if (!glfwInit())
		exit(EXIT_FAILURE);
 
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 2);
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
	
	const GLFWvidmode* mode = glfwGetVideoMode(glfwGetPrimaryMonitor());
 
	int monitor_width = mode->width; // Monitor's width.
	int monitor_height = mode->height;
 
	int window_width = (int)(monitor_width * 0.5f); // Window size will be 50% the monitor's size...
	int window_height = (int)(monitor_height * 0.5f); // ... Cast is simply to silence the compiler warning.
 
	GLFWwindow* window = glfwCreateWindow(window_width, window_height, "GLFW Test Window – Changing Colours", NULL, NULL);
	// GLFWwindow* window = glfwCreateWindow(window_width, window_height, "Drawing Basic Shapes - Buffer Objects & Shaders", glfwGetPrimaryMonitor(), NULL); // Full Screen Mode ("Alt" + "F4" to Exit!)
 
	if (!window)
	{
		glfwTerminate();
		exit(EXIT_FAILURE);
	}
 
	glfwMakeContextCurrent(window); // Set the window to be used and then centre that window on the monitor. 
	glfwSetWindowPos(window, (monitor_width - window_width) / 2, (monitor_height - window_height) / 2);
 
	glfwSwapInterval(1); // Set VSync rate 1:1 with monitor's refresh rate.
 
	// (2) GLAD: Load OpenGL Function Pointers
	// -------------------------------------------------------
	if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress)) // For GLAD 2 use the following instead: gladLoadGL(glfwGetProcAddress)
	{
		glfwTerminate();
		exit(EXIT_FAILURE);
	}
 
	// (3) Enter the Main-Loop
	// --------------------------------	
	float red = 0.0f; // Set individual colours here: OpenGL RGB [0, 1] = Actual RGB / 255
	float green = 0.35f;
	float blue = 0.7f;
 
	int red_dir = 1; // Colour change direction.
	int green_dir = 1;
	int blue_dir = 1;
 
	while (!glfwWindowShouldClose(window)) // Main-Loop
	{
		red += 0.02f * red_dir; // Increase or decrease colour values.
		green += 0.03f * green_dir;
		blue += 0.04f * blue_dir;
 
		if (red > 1 || red < 0) // Reverse the colour changing direction.
			red_dir = -red_dir;
 
		if (green > 1 || green < 0)
			green_dir = -green_dir;
 
		if (blue > 1 || blue < 0)
			blue_dir = -blue_dir;
 
		std::cout << "Red: " << red << " --- Green: " << green << " --- Blue: " << blue << std::endl;
 
		glClearColor(red , green, blue, 1.0f);
		glClear(GL_COLOR_BUFFER_BIT); // Clear the screen with... red, green, blue.
 
		glfwSwapBuffers(window);
		glfwPollEvents();
	}
	
	/* glfwDestroyWindow(window) // Call this function to destroy a specific window */
	glfwTerminate(); // Destroys all remaining windows and cursors, restores modified gamma ramps, and frees resources.
 
	exit(EXIT_SUCCESS); // Function call: exit() is a C/C++ function that performs various tasks to help clean up resources.
}