Failing to create GLFW window - c++

Question

I want to create a share GLFW window but GLFW is not able to create the second window.
i am able to create a single window but not two windows
This is my code.
I want to use the second window in another thread so i can share their context.
#include "pch.h"
#include <iostream>
#include <gl\glew.h>
#include <glfw3.h>
int SCR_WIDTH = 1920;
int SCR_HEIGHT = 1080;
int main()
{
glfwInit();
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
// glfw window creation
// --------------------
GLFWwindow* sharedWindow = NULL;
GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", 0, sharedWindow);
if (window == NULL)
{
std::cout << "Failed to create the first GLFW window" << std::endl;
glfwTerminate();
return -1;
}
if (sharedWindow == NULL)
{
std::cout << "Failed to create the second GLFW window" << std::endl;
// glfwTerminate();
// return -1;
}
while (true)
{
}
std::cout << "Hello World!\n";
}

Answer 1

share is an input parameter. See glfwCreateWindow.
Create the first window and call glfwCreateWindow a 2nd time for the 2nd window:
GLFWwindow* wnd = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", 0, nullptr);
GLFWwindow* wnd2 = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "window 2", 0, window);
The window can even be created in a separate thread, but note you've to ensure that the OpenGL context of the 1st window is not current when you create the 2nd window.
#include <thread>
#include <mutex>
#include <condition_variable>
GLFWwindow *wnd = nullptr;
bool wnd2created = false;
std::mutex mtx;
std::condition_variable cv;
void wnd2func( void )
{
GLFWwindow *wnd2 = glfwCreateWindow( 800, 600, "window 2", nullptr, wnd );
{
std::unique_lock<std::mutex> lck(mtx);
wnd2created = true;
cv.notify_one();
}
if (wnd2 == nullptr)
return;
glfwMakeContextCurrent(wnd2);
// [...]
}
int main()
{
// [...]
wnd = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", 0, nullptr);
if (wnd == nullptr)
return -1;
std::thread wnd2thread(wnd2func);
{
std::unique_lock<std::mutex> lck(mtx);
cv.wait(lck, []() -> bool { return wnd2created; });
}
glfwMakeContextCurrent(wnd);
// [...]
}