Question

I want to add the option when the menu is called with the right click on mouse to change the values of a colour by user input.
I tried cin>> RED1; but it doesn’t identify cin.
I have no clue how to make this work except by giving a fixed value to change the colours. How can I achieve user input on this case?

#include <stdio.h>
#include <stdlib.h>
#include <iostream>
#include <string>
#define _USE_MATH_DEFINES
#include <cmath>
#include <gl/glut.h>

GLfloat angle = 0.0;
static int RED1 = 1, GREEN1 = 3, BLUE1 = 0, RED2 = 2, GREEN2 = 2, BLUE2 = 1;
static int MENUsub, Face1, Face2, i, LINES;
static int SELECIONA = 2, f = 0, VALOR = 0, SOLID = 0, LINE = 1;
static double NoFaces = 32, ihc, cordX = 1, cordY = 1, cordZ = 1;

void init(void)
{
    glClearColor (0.0, 0.0, 0.0, 0.0);
    glShadeModel (GL_FLAT);
}

void creatMENU(void)
{
    Face1 = glutCreateMenu(MENU);

    glutAddMenuEntry("Change Colour Values", 1);

    MENUsub = glutCreateMenu(MENU);

    glutAddSubMenu("Face 1", Face1);

    glutAddMenuEntry("Sair", 0);
    glutAttachMenu(GLUT_RIGHT_BUTTON);
}

void MENU (int OPT)
{
    if(OPT == 0)
    {
        exit(0);
    }
    else
    {
        switch(OPT);
        {
        case 1 :
            //cin>> RED1;
            RED1 = 2;
            break;
        }
    }
}

Answer 1

As far as I know, you’ll need to handle it yourself.

Use the glutKeyboardFunc to get keyboard input, and use glutBitmapCharater to print text to the window.

So you can keep a global bool changingColor which you can switch to true when the menu item is selected. You can then render the input using a rectangle or something. You might have a keyboard function that looks a little like this:

std::string colorInput;

void keyboard(unsigned char key, int x, int y) {
    if (changingColor) {
        colorInput += key;
    }
 }

And in your rendering function, something like:

if (changingColor) {
    glRasterPos3f(x, y, z);
    for (auto it = colorInput.begin(); it != colorInput.end(); ++it) {
        glutBitmapCharacter(GLUT_BITMAP_HELVETICA_10, *it);
    }
}

1. glutBitmapCharacter
2. glutKeyboardFunc