OpenGL Window Resizing

  c++, glfw, opengl

I am trying to make my program able to handle window resizing without losing the aspect ratio with little luck. Most online searches led me to old questions using legacy code while I am working on OpenGL 3.3. So far what I have tried is using glfwSetWindowSizeCallback and glfwSetWindowSize but end up with the image not taking the new space as seen in the picture:

enter image description here

Source: Windows Questions C++