如何将 opengl window 与 glfw 居中？

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;
}