How to Resize "SubWindow" in FreeGLUT?

Question

I need my main window and subwindow to be resized when I make the window larger or smaller. For the subwindow, it should resize automatically when the main window is resized. Meanwhile, I also need to protect the aspect ratio of both of my windows. I achieved this for my main window, but I can't resize or protect the aspect ratio of the subwindow using FreeGLUT. What is the proper way of doing this in FreeGLUT?

I tried using glutReshapeFunc() for the subwindow, however it still does not resize the subwindow. Indeed, when I applied the same steps for my main window it protected the ratio perfectly. This is the code and what I tried:

#include <GL/glut.h>

using namespace std;

void display(void);
void reshape(int width, int height);
void drawGrid(void);

const float gridSize = 20;

void drawGrid()
{
    //vertical grid lines
    glColor3f(1, 1, 0);
    glLineStipple(1, 0xAAAA);
    glEnable(GL_LINE_STIPPLE);

    glBegin(GL_LINES);

    for (int i = 0; i <= 100; i += gridSize) {
        glVertex2f(i, -100);
        glVertex2f(i, 100);
    }

    //horizontal grid lines
    for (int i = -100; i <= 100; i += gridSize) {
        glVertex2f(0, i);
        glVertex2f(100, i);
    }

    glEnd();
    glDisable(GL_LINE_STIPPLE);
}

void display() {
    glClear(GL_COLOR_BUFFER_BIT);

    drawGrid();

    glutSwapBuffers();
}

void reshape(int width, int height) {
    glViewport(0, 0, width, height);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();

    float aspectRatio = static_cast<float>(width) / static_cast<float>(height);

    if (aspectRatio > 1.0) {
        gluOrtho2D(-10 * aspectRatio, 110 * aspectRatio, -110, 110);
    }
    else {
        gluOrtho2D(-10, 110, -110 / aspectRatio, 110 / aspectRatio);
    }

    glMatrixMode(GL_MODELVIEW);
}


int main(int argc, char** argv) {
    glutInit(&argc, argv);
    glutInitWindowSize(512, 512);
    glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE);

    int mainWindow = glutCreateWindow("Main Window");
    glutDisplayFunc(display);
    glutReshapeFunc(reshape);

    int subWindow = glutCreateSubWindow(mainWindow, 50, 50, 412, 412);
    glutDisplayFunc(display);
    glutReshapeFunc(reshape);

    glutMainLoop();
    return 0;
}