Is there a way to prevent the contents of my window from "moving" when i resize the window in OpenGL

  c++, glfw, opengl, opengl-3, viewport

I would like my window contents to stay centered when my window resizes. OpenGL (or GLFW) – I’m not sure which – does give this desired effect when resizing horizontally, however when i resize the window vertically the window appears to show the more of the bottom of the cube. I expected it to cut off the cube like when resizing horizontally,

This is the horizontal resize
Horizontal Resize

And this is the vertical resize
Vertical Resize

Note: I do not make any glViewPort() otherwise the window contents would adjust to the new width and height.

Is there any way to change this behaviour? This question may be related but i don’t believe that is solves my problem. How to keep the OpenGL viewport in an SDL window stationary …

#include <iostream>
#include <GL/glew.h>
#include <GL/gl.h>
#include <GLFW/glfw3.h>

#include "../includes/Shader.h"
#include "../includes/Texture.h"
#include "../includes/glm/glm.hpp"


const int SCR_WIDTH = 800;
const int SCR_HEIGHT = 600;

void framebuffer_size_callback(GLFWwindow *window, int width, int height);

void processInput(GLFWwindow *window);

int main() {

    glfwInit();
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
    
    GLFWwindow *window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "OpenGL", nullptr, nullptr);
    if (window == nullptr) {
        std::cout << "Failed to create window! " << std::endl;
        glfwTerminate();
        return -1;
    }

    glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
    glfwMakeContextCurrent(window);

    if (glewInit() != GLEW_OK) {
        std::cout << "Failed to initialize GLEW! " << std::endl;
        glfwTerminate();
        return -1;
    }

    float vertices[] = {
            ...
    };

    unsigned int VAO, VBO;

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

    glBindVertexArray(VAO);
    glBindBuffer(GL_ARRAY_BUFFER, VBO);

    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(float) * 5, (GLvoid *) nullptr);
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, sizeof(float) * 5, (GLvoid *) (sizeof(float) * 3));
    glEnableVertexAttribArray(1);

    glBindBuffer(GL_ARRAY_BUFFER, 0);
    glBindVertexArray(0);

    Texture texture1("../images/container.jpg");
    Texture texture2("../images/awesomeface.png");

    Shader shader("../shaders/shader.vs", "../shaders/shader.fs");

    shader.use();
    shader.setUniform1i("texture1", 0);
    shader.setUniform1i("texture2", 1);


    while (!glfwWindowShouldClose(window)) {

        processInput(window);

        glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
        glEnable(GL_DEPTH_TEST);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

        texture1.bind(0);
        texture2.bind(1);

        glm::mat4 model = glm::mat4(1.0f);
        glm::mat4 view = glm::mat4(1.0f);
        glm::mat4 projection = glm::mat4(1.0f);

        model = glm::rotate(model, (float) glfwGetTime(), glm::vec3(1.0f, 0.5f, 0.5f));
        view = glm::translate(view, glm::vec3(0.0f, 0.0f, -3.0f));
        projection = glm::perspective(glm::radians(45.0f), 800.0f/600.0f, 0.1f, 100.0f);

        shader.setUniformMat4("model", model);
        shader.setUniformMat4("view", view);
        shader.setUniformMat4("projection", projection);

        glBindVertexArray(VAO);
        glDrawArrays(GL_TRIANGLES, 0, 36);
        glBindVertexArray(0);

        glfwSwapBuffers(window);
        glfwPollEvents();
    }

    glDeleteVertexArrays(1, &VAO);
    glDeleteBuffers(1, &VBO);

    glfwTerminate();
    return 0;
}

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

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

Source: Windows Questions C++

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