What it is
GLFW is an open-source library for creating windows, contexts, and handling input and events in OpenGL, OpenGL ES, and Vulkan applications. It is designed to be simple, portable, and lightweight, ideal for graphics and game development.
GLFW provides functions to create windows, handle keyboard and mouse input, manage OpenGL or Vulkan contexts, and handle events. It supports multiple monitors, full-screen modes, and high-DPI scaling.
Installation
sudo apt install libglfw3-devGetting started
The smallest useful thing you can do with it, and what each part means.
#include <GLFW/glfw3.h>
#include <iostream>
int main() {
if (!glfwInit()) {
std::cerr << "Failed to initialize GLFW" << std::endl;
return -1;
}
GLFWwindow* window = glfwCreateWindow(640, 480, "Hello GLFW", nullptr, nullptr);
if (!window) {
glfwTerminate();
return -1;
}
glfwMakeContextCurrent(window);
while (!glfwWindowShouldClose(window)) {
glClear(GL_COLOR_BUFFER_BIT);
glfwSwapBuffers(window);
glfwPollEvents();
}
glfwDestroyWindow(window);
glfwTerminate();
return 0;
}void key_callback(GLFWwindow* window, int key, int scancode, int action, int mods) {
if (key == GLFW_KEY_ESCAPE && action == GLFW_PRESS)
glfwSetWindowShouldClose(window, true);
}
int main() {
glfwInit();
GLFWwindow* window = glfwCreateWindow(640, 480, "Input Example", nullptr, nullptr);
glfwMakeContextCurrent(window);
glfwSetKeyCallback(window, key_callback);
while (!glfwWindowShouldClose(window)) {
glfwSwapBuffers(window);
glfwPollEvents();
}
glfwDestroyWindow(window);
glfwTerminate();
return 0;
}Advanced usage
Where the library earns its place over a simpler alternative.
void mouse_callback(GLFWwindow* window, double xpos, double ypos) {
std::cout << "Mouse moved to: (" << xpos << ", " << ypos << ")" << std::endl;
}
int main() {
glfwInit();
GLFWwindow* window = glfwCreateWindow(640, 480, "Mouse Example", nullptr, nullptr);
glfwMakeContextCurrent(window);
glfwSetCursorPosCallback(window, mouse_callback);
while (!glfwWindowShouldClose(window)) {
glfwSwapBuffers(window);
glfwPollEvents();
}
glfwDestroyWindow(window);
glfwTerminate();
return 0;
}GLFWmonitor* primary = glfwGetPrimaryMonitor();
const GLFWvidmode* mode = glfwGetVideoMode(primary);
GLFWwindow* window = glfwCreateWindow(mode->width, mode->height, "FullScreen", primary, nullptr);glfwSwapInterval(1);GLFWwindow* window1 = glfwCreateWindow(400, 300, "Window 1", nullptr, nullptr);
GLFWwindow* window2 = glfwCreateWindow(400, 300, "Window 2", nullptr, window1);Errors and fixes
The failures you are most likely to hit, and what actually resolves them.
- GLFW_NOT_INITIALIZED
- Ensure `glfwInit()` is called successfully before using other GLFW functions.
- Failed to create GLFW window
- Verify that the requested video mode and context hints are supported by your system.
- OpenGL context not current
- Call `glfwMakeContextCurrent(window)` before issuing OpenGL commands.
Best practices
- Always call `glfwTerminate()` before exiting to clean up resources.
- Use callbacks for input handling rather than polling for cleaner code.
- Check return values of GLFW functions to handle initialization or creation errors.
- Use `glfwSwapInterval(1)` for smoother rendering.
- Keep rendering and event polling in separate loops for responsive UI.
Background
Why it exists, and what it was reacting to.
GLFW was created by Camilla Löwy to provide a simple, cross-platform API for creating windows and managing input in graphics applications. It abstracts platform-specific details and integrates smoothly with OpenGL, making it a popular choice for developers building real-time graphics, games, and simulations.