using a global glfw window in multiple functions - c++

Question

I Have a int main(); function and a int Game(); function where in the main function I have a window I use in both functions. I have defined the window in the global scope and when I try to run the Game(); function before GLFW loop in main function the window opens for a second and then closes. I then get
Error: The GLFW library is not initialised
printed from error_callback();
Here's My Code
#include <GLFW/glfw3.h>
#include <GL/freeglut.h>
#include <GL/GL.h>
#include <stdio.h>
#include <string>
#include <iostream>
using namespace std;
void drawText(const char *text, int length, int x, int y);
void framebuffer_size_callback(GLFWwindow* wndow, int width, int height);
void DrawCube(GLfloat centerPosX, GLfloat centerPosY, GLfloat centerPosZ, GLfloat edgeLength);
void button(GLfloat red, GLfloat green, GLfloat blue, int x, int y, int width, int height);
void error_callback(int error, const char* description);
int Game();
int width = 860, height = 490;
GLFWwindow* window;
int main(int argc, char **argv) {
//GLTtext* text = gltCreateText();
//gltSetText(text, "ElectroCraft");
//GLFWwindow* window;
int width = 860, height = 490;
if (!glfwInit()) {
printf("failed to init glfw");
return -1;
}
glutInit(&argc, argv);
window = glfwCreateWindow(width, height, "ElectroCraft", NULL, NULL);
glfwMakeContextCurrent(window);
if (!window) {
printf("failed to start window");
glfwTerminate();
return -1;
}
Game();
glEnable(GL_DEPTH_TEST);
glViewport(0, 0, width, height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0, width, 0, height, 0, 1000);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
string text;
glfwSetErrorCallback(error_callback);
while (!glfwWindowShouldClose(window)) {
glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
glClearColor(53.0f / 255.0f, 81.0f / 255.0f, 92.0f / 255.0f, 0.0f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glBegin(GL_LINES);
glVertex2f(0, height-80);
glVertex2f(width, height - 80);
glEnd();
button(192.0f / 255.0f, 192.0f / 255.0f, 192.0f / 255.0f, width / 2 - 70, height / 2, 260, 50);
glfwSwapBuffers(window);
glfwPollEvents();
}
glfwTerminate();
return 1;
}
void error_callback(int error, const char* description) {
fprintf(stderr, "Error: %s\n", description);
}
int Game() {
//glfwMakeContextCurrent(window);
glEnable(GL_DEPTH_TEST);
glViewport(0, 0, width, height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0, width, 0, height, 0, 1000);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
while (!glfwWindowShouldClose) {
glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
glClearColor(62.0f / 255.0f, 85.9f / 255.0f, 255.0 / 255.0, 0.0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glfwSwapBuffers(window);
glfwPollEvents();
}
glfwTerminate();
return 1;
}
This could be because I didn't initiate the GLFW library globally but I couldn't seem to do this as I got an error if a if statement was outside of a function

Answer 1

the window opens for a second and then closes
Of course, because glfwWindowShouldClose in not a function call in the function Game. glfwWindowShouldClose is a function pointer, so !glfwWindowShouldClose evaluates to false and the loop never runs:
while (!glfwWindowShouldClose) {
while (!glfwWindowShouldClose(window)) {
I then get Error: The GLFW library is not initialised
This is because GLFW is terminated by glfwTerminate() in the function Game. Delete glfwTerminate() from the function Game.
But note, once you've closed a window, you've to create a new window. An option would be to hide glfwHideWindow and show glfwShowWindow a window.