Trouble with getting console input after opening and closing GLFW window - c

Question

I am developing an application using GLFW, whereby the user can input some information into the console, the program does some processing on the information, then opens an opengl window (using GLFW) to display the results. The user can then close the window, and be returned to the main menu and enter more information if they want.
Currently the problem I'm having is that once closing the GLFW/OpenGL window the console no longer accepts any input from scanf(). I am fairly certain that I am closing GLFW properly, so I am unsure as to what the problem is.
The code I am using is below:
Main.c:
#include <stdio.h>
#include <stdlib.h>
#include "glfw.h"
#include "pantograph.h"
int main(int argc, char** argv)
{
printf("program start");
int a = 0;
scanf("%i",&a); //this works
printf("%c",a);
p_open_window(1000, 500, 0, "hi there");
int i = 0;
for(i=0;i<1000;i++)
{
p_begin_render();
glBegin(GL_POINTS);
glVertex2i(i,i/2);
glEnd();
scanf("%i",&a);
p_end_render();
}
p_close_window();
scanf("%i",&a); //this does not work
printf("%i",a);
return 0;
}
pantograph.h:
int p_open_window(int width, int height, int fullscreen, const char* title)
{
glfwInit();
glfwDisable(GLFW_AUTO_POLL_EVENTS);
if(fullscreen)
{
glfwOpenWindow(width,height,8,8,8,8,0,0,GLFW_FULLSCREEN);
}else{
glfwOpenWindowHint(GLFW_WINDOW_NO_RESIZE, GL_TRUE);
glfwOpenWindow(width,height,8,8,8,8,0,0,GLFW_WINDOW);
}
glViewport(0, 0, width, height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0, width, height, 0, 0, 1);
glMatrixMode(GL_MODELVIEW);
glDisable(GL_DEPTH_TEST);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
return 1;
}
void p_begin_render()
{
glClearColor(0.0, 0.0, 0.0, 1.0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glColor4f(1.0, 1.0, 1.0, 1.0);
glLoadIdentity();
}
void p_end_render()
{
glfwSwapBuffers();
}
void p_close_window()
{
glfwCloseWindow();
glfwTerminate();
}

Answer 1

I'm a little confused by your program flow. You say 'the user can close the window and be returned to the main menu'. But how does the program exit from the (i<1000) loop? If the user just closes the window it seems like it would still be executing the for loop (especially because of the scanf inside the loop).
Have you used a debugger to see which point your program gets caught on?

Answer 2

Thanks to the people at #glfw I've managed to find a somewhat hackish solution...
If you "flush" the input buffer directly after closing the glfw window scanf will start to work again. I'm not entirely sure why, but it seems to work for now, so I'm satsfied.
The code I'm using to do it is as follows (after closing the window):
int ch;
while ((ch = getchar()) != '\n' && ch != EOF);
After this, scanf began working again.