Finish drawing a polygon by right-clicking, but displaying a menu instead

Question

I am writing a program that will continuously draw a polygon until the user right-clicks. The user can only draw if and only if the user makes a selection in the menu, if the user does not make a selection in the menu, the program will not draw. Up to now, my program has successfully drawn a polygon with the mouse, but the problem is that when I right-click to complete, the program pops up the menu instead of completing the polygon. Now how can I right-click to be able to complete the polygon, here's my program:

const int MAX = 100;
float mouseX, mouseY, ListX[MAX], ListY[MAX];
int numPoints = 0, closed = 0, shape = 0;

void mouse(int button, int state, int x, int y)
{
    mouseX = x;
    mouseY = y;

    if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN)
    {
        if (closed || numPoints >= MAX - 1)
            numPoints = 0;
        closed = 0;
        ListX[numPoints] = mouseX;
        ListY[numPoints] = mouseY;
        numPoints++;
    }
    if (button == GLUT_RIGHT_BUTTON && state == GLUT_DOWN)
        closed = 1;
}

void motion(int x, int y)
{
    mouseX = x;
    mouseY = y;
    glutPostRedisplay();
}

void display()
{
    glClear(GL_COLOR_BUFFER_BIT);
    if (shape == 1)
    {
        if (numPoints)
        {
            glBegin(GL_LINE_STRIP);
            for (int i = 0; i < numPoints; ++i)
                glVertex2f(ListX[i], ListY[i]);
            if (closed)
                glVertex2f(ListX[0], ListY[0]);
            else
                glVertex2f(mouseX, mouseY);
            glEnd();
        }
    }
    glFlush();
}

void menu(int choice)
{
    switch (choice)
    {
    case 1:
        shape = 1;
        break;
    }
}

int main(int argc, char** argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
    glutInitWindowSize(640, 480);
    glutInitWindowPosition(100, 100);
    glutCreateWindow("");
    gluOrtho2D(0, 640, 480, 0);

    glutCreateMenu(menu);
    glutAddMenuEntry("Polygon", 1);
    glutAttachMenu(GLUT_RIGHT_BUTTON);

    glutDisplayFunc(display);
    glutMouseFunc(mouse);
    glutPassiveMotionFunc(motion);
    
    glutMainLoop();
}

Edit: Thanks to genpfault, I finished the polygon by right-clicking but I don't know how to reattach it so I can re-open the menu.

...

void display()
{
    glClear(GL_COLOR_BUFFER_BIT);
    if (shape == 1)
    {
        glutDetachMenu(GLUT_RIGHT_BUTTON); // Add this

        ...
    }
    glFlush();
}

void menu(int choice)
{
    switch (choice)
    {
    case 1:
        shape = 1;
        break;
    }
}

int main(int argc, char** argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
    glutInitWindowSize(640, 480);
    glutInitWindowPosition(100, 100);
    glutCreateWindow("");
    gluOrtho2D(0, 640, 480, 0);

    glutCreateMenu(menu);
    glutAddMenuEntry("Polygon", 1);
    glutAttachMenu(GLUT_RIGHT_BUTTON);

    glutDisplayFunc(display);
    glutMouseFunc(mouse);
    glutPassiveMotionFunc(mouse_move);

    glutMainLoop();
}

Answer 1

1. Capture the return-value from glutCreateMenu(), that's the handle for the new menu.
2. Detach the menu in the menu callback via glutDetachMenu() and set a bool indicating you're in "add points" mode.
3. If you're in "add points" mode and detect a right-click, set the current menu to the menu handle from #1 via glutSetMenu(), then re-attach the menu with glutAttachMenu(). Reset the "add points" bool to false.

All together:

#include <GL/glut.h>

const int MAX = 100;
float mouseX, mouseY, ListX[MAX], ListY[MAX];
int numPoints = 0, closed = 0, shape = 0;

int hMenu = 0;
bool addingPoints = false;

void mouse(int button, int state, int x, int y)
{
    mouseX = x;
    mouseY = y;

    if( addingPoints )
    {
        if( button == GLUT_LEFT_BUTTON && state == GLUT_DOWN )
        {
            if (closed || numPoints >= MAX - 1)
                numPoints = 0;
            closed = 0;
            ListX[numPoints] = mouseX;
            ListY[numPoints] = mouseY;
            numPoints++;
        }
        if( button == GLUT_RIGHT_BUTTON && state == GLUT_DOWN )
        {
            closed = 1;

            addingPoints = false;
            glutSetMenu(hMenu);
            glutAttachMenu(GLUT_RIGHT_BUTTON);
        }
    }
}

void motion(int x, int y)
{
    mouseX = x;
    mouseY = y;
    glutPostRedisplay();
}

void display()
{
    glClear(GL_COLOR_BUFFER_BIT);

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0, 640, 480, 0, -1, 1);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    if (shape == 1)
    {
        if (numPoints)
        {
            glBegin(GL_LINE_STRIP);
            for (int i = 0; i < numPoints; ++i)
                glVertex2f(ListX[i], ListY[i]);
            if (closed)
                glVertex2f(ListX[0], ListY[0]);
            else
                glVertex2f(mouseX, mouseY);
            glEnd();
        }
    }
    glutSwapBuffers();
}

void menu(int choice)
{
    switch (choice)
    {
    case 1:
        numPoints = 0;
        shape = 1;

        addingPoints = true;
        glutDetachMenu(GLUT_RIGHT_BUTTON);
        break;
    }
}

int main(int argc, char** argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
    glutInitWindowSize(640, 480);
    glutCreateWindow("");

    hMenu = glutCreateMenu(menu);
    glutSetMenu(hMenu);
    glutAddMenuEntry("Polygon", 1);
    glutAttachMenu(GLUT_RIGHT_BUTTON);

    glutDisplayFunc(display);
    glutMouseFunc(mouse);
    glutPassiveMotionFunc(motion);

    glutMainLoop();
}