How to center an opengl window with glfw? - c++

Question

I wanna draw an opengl window in center of the screen，however I searched everywhere but didn't find any answer to it. Below is a common snippet code of creating a window But it always show up in most left-top position.How can I control it.
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(400,200,"LearnOpenGl",NULL,NULL);
if(window == NULL)
{
cout<<"Failed to create GLFW window!!"<<endl;
glfwTerminate();
return -1;
}
glfwMakeContextCurrent(window);
if(!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
{
cout<<"Failed to initialize GLAD!!"<<endl;
return -1;
}
glViewport(400, 400, 100, 200);
glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
while(!glfwWindowShouldClose(window))
{
glfwSwapBuffers(window);
glfwPollEvents();
}
}

Answer 1

Please use this function "glfwSetWindowPos".
Here is an example.

Answer 2

#Himanshu answered a question on how to get the max-width and max-height of a window aka window size How to get maximum possible window size when creating window in MFC?
So with that piece of code, you can center it like below:
int width=800;// could declare them as "const int" if you like
int hight=800;
GLFWwindow* window = glfwCreateWindow(width,hight, "OpenGL", NULL, NULL);
int max_width = GetSystemMetrics(SM_CXSCREEN);
int max_hieght = GetSystemMetrics(SM_CYSCREEN);
glfwSetWindowMonitor(window, NULL, (max_width/2)-(width/2), (max_hieght/2) - (height/2), width, height, GLFW_DONT_CARE);

Answer 3

Here is a sample from my game engine made using glad and glfw it uses the windows api to find to screen resolution and then centers the window accordingly.
#include <iostream>
#include <glad/glad.h>
#include <glm/glm.hpp>
#include <GLFW/glfw3.h>
#include <Windows.h>
const unsigned int width = 1600;
const unsigned int height = 900;
const char* title = "Frog2D";
void getDesktopResolution(int& horizontal, int& vertical)
{
RECT desktop;
const HWND hDesktop = GetDesktopWindow();
GetWindowRect(hDesktop, &desktop);
horizontal = desktop.right;
vertical = desktop.bottom;
}
int main()
{
glfwInit();
glfwDefaultWindowHints();
glfwWindowHint(GLFW_VISIBLE, GL_TRUE);
glfwWindowHint(GLFW_RESIZABLE, GL_TRUE);
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
glfwWindowHint(GLFW_DECORATED, GLFW_FALSE); //borderless
int horizontal = 0;
int vertical = 0;
getDesktopResolution(horizontal, vertical);
GLFWwindow* window = glfwCreateWindow(width, height, title, NULL, NULL);
glfwSetWindowPos(window, horizontal / 2 - width / 2, vertical / 2 - height / 2);
return 0;
}