Question

I am trying to create a menu after inputting text from where the cursor is located in openGL window in C++. The menu needs to be able to change color and font of text and also have an option to quit the program. For some reason my program is not working. First the words won’t display when I start typing. Then when I click on a color it quits the program. How do I fix this?

My code is below:

#include // include iostream library
#include // include cmath library
#include <GL/glut.h> // include GLUT library
#include

//***********************************************************************************
void drawAxis()
{
glPointSize(1); // change point size back to 1
glBegin(GL_POINTS); // use points to form X-/Y-axes
glColor3f(0, 0, 0); // change drawing color to black
for (int x = -150; x <= 150; x++) // draw X-axis
glVertex2i(x, 0);
for (int y = -150; y <= 150; y++) // draw Y-axis
glVertex2i(0, y);
glEnd();

glRasterPos2i(150, 5);
glutBitmapCharacter(GLUT_BITMAP_TIMES_ROMAN_10, 'X');
glRasterPos2i(5, 150);
glutBitmapCharacter(GLUT_BITMAP_TIMES_ROMAN_10, 'Y');

}

//***********************************************************************************
void myInit()
{
glClearColor(1, 1, 1, 0); // specify a background clor: white
gluOrtho2D(-200, 200, -200, 200); // specify a viewing area
}

//***********************************************************************************
void myDisplayCallback()
{
glClear(GL_COLOR_BUFFER_BIT); // draw the background
drawAxis();
glFlush(); // flush out the buffer contents
}

bool started = false;
int x, y = -1000;
int r, g, b = 0;
float offset = 0;
std::string message = “”;
void myKeyboardCallback(unsigned char key, int cursorX, int cursorY) {
message += key;
myDisplayCallback();
if (started == false) {
x = cursorX - 200;
y = 200 - cursorY;
}
glColor3f(r, g, b);
glRasterPos2i(x, y);
for (int i = 0; i < message.length(); i++) {
glutBitmapCharacter(GLUT_BITMAP_9_BY_15, message[i]);
}

started = true;
glFlush();

}

void myMenuCallback(int value)
{
switch (value)
{
case 1:
r = 1;
g = 0;
b = 0;
glColor3f(r, g, b);
glRasterPos2i(x, y);
for (int i = 0; i < message.length(); i++) {
glutBitmapCharacter(GLUT_BITMAP_9_BY_15, message[i]);
}
case 2:
r = 0;
g = 0;
b = 1;
glColor3f(r, g, b);
glRasterPos2i(x, y);
for (int i = 0; i < message.length(); i++) {
glutBitmapCharacter(GLUT_BITMAP_9_BY_15, message[i]);
}
case 3:
r = 0;
g = 1;
b = 0;
glColor3f(r, g, b);
glRasterPos2i(x, y);
for (int i = 0; i < message.length(); i++) {
glutBitmapCharacter(GLUT_BITMAP_9_BY_15, message[i]);
}
case 4:
exit(0);
break;
}

myDisplayCallback();

glFlush();

}
void myMotionCallback(int cursorX, int cursorY) {
myDisplayCallback();
glColor3f(r, g, b);
x = cursorX - 200;
y = 200 - cursorY;
glRasterPos2i(x, y);
for (int i = 0; i < message.length(); i++) {
glutBitmapCharacter(GLUT_BITMAP_9_BY_15, message[i]);
}
glFlush();
}

//***********************************************************************************
int main(int argc, char** argv)
{ glutInit(& argc, argv); // optional in our environment
//getUserInput();
glutInitWindowSize(400, 400); // specify a window size
glutInitWindowPosition(100, 0); // specify a window position
glutCreateWindow(“Simple Text Drawing”); // create a titled window
myInit(); // setting up
glutDisplayFunc(myDisplayCallback); // register a callback
glutKeyboardFunc(myKeyboardCallback);

int sub1 = glutCreateMenu(myMenuCallback);

glutAddMenuEntry("Red", 1);
glutAddMenuEntry("Blue", 2);
glutAddMenuEntry("Green", 3);
glutCreateMenu(myMenuCallback);
glutAddSubMenu("Colors", sub1);

glutAddMenuEntry("Exit", 4);
glutAttachMenu(GLUT_RIGHT_BUTTON);

glutMotionFunc(myMotionCallback);
glutMainLoop();                                                 // get into an infinite loop
return 0;

}

Answer 1

// when start your program curser must be within this window

#include <iostream>// include iostream library
#include <cmath>// include cmath library
#include <GL/glut.h> // include GLUT library

using namespace std;
int ch = 0;

//***********************************************************************************
void drawAxis()
{
   glPointSize(1); // change point size back to 1
   glBegin(GL_POINTS); // use points to form X-/Y-axes
   glColor3f(0, 0, 0); // change drawing color to black
   for (int x = -150; x <= 150; x++) // draw X-axis
       glVertex2i(x, 0);
   for (int y = -150; y <= 150; y++) // draw Y-axis
       glVertex2i(0, y);
   glEnd();

   glRasterPos2i(150, 5);
   glutBitmapCharacter(GLUT_BITMAP_TIMES_ROMAN_10, 'X');
   glRasterPos2i(5, 150);
   glutBitmapCharacter(GLUT_BITMAP_TIMES_ROMAN_10, 'Y');
}

//***********************************************************************************
void myInit()
{
   glClearColor(1, 1, 1, 0); // specify a background clor: white
   gluOrtho2D(-200, 200, -200, 200); // specify a viewing area
}

//***********************************************************************************
void myDisplayCallback()
{
   glClear(GL_COLOR_BUFFER_BIT); // draw the background
   drawAxis();
   glFlush(); // flush out the buffer contents
}

bool started = false;
int x, y = -1000;
int r, g, b = 0;
float offset = 0;
std::string message = "";
void myKeyboardCallback(unsigned char key, int cursorX, int cursorY) {
   message += key;
   myDisplayCallback();
   if (started == false) {
       x = cursorX - 200;
       y = 200 - cursorY;
   }
   glColor3f(r, g, b);
   glRasterPos2i(x, y);
   for (int i = 0; i < message.length(); i++) {
       glutBitmapCharacter(GLUT_BITMAP_9_BY_15, message[i]);
   }

   started = true;
   glFlush();
}

void myMenuCallback(int value)
{
   switch (value)
   {
   case 1: {
       r = 1;
       g = 0;
       b = 0;
       glColor3f(r, g, b);
       glRasterPos2i(x, y);
      
       ch = 1;
       break; }

   case 2: {
       r = 0;
       g = 0;
       b = 1;
       glColor3f(r, g, b);
       glRasterPos2i(x, y);
      
       ch = 2;
       break;
   }
   case 3: {
       r = 0;
       g = 1;
       b = 0;
       glColor3f(r, g, b);
       glRasterPos2i(x, y);
      
       ch = 3;
       break; }
   case 4: {
       exit(0);
       break;
       }
   case 5: {
      
       ch = 5;
       break;
   }

   case 6: {
      
       ch = 6;
       break;
   }
   case 7: {
      
       ch = 7;
       break;
   }
   case 8: {
      
       ch = 8;
       break;
   }
   case 9: {
      
       ch = 9;
       break;
   }
   }

   myDisplayCallback();
}

void myMotionCallback(int cursorX, int cursorY) {
   myDisplayCallback();
   glColor3f(r, g, b);
   x = cursorX - 200;
   y = 200 - cursorY;
   glRasterPos2i(x, y);
   for (int i = 0; i < message.length(); i++) {
       if(ch==5){ glutBitmapCharacter(GLUT_BITMAP_TIMES_ROMAN_10, message[i]); }
       if (ch == 6) { glutBitmapCharacter(GLUT_BITMAP_TIMES_ROMAN_24, message[i]); }
       if (ch == 7) { glutBitmapCharacter(GLUT_BITMAP_HELVETICA_10, message[i]); }
       if (ch == 8) { glutBitmapCharacter(GLUT_BITMAP_HELVETICA_12, message[i]); }
       if (ch == 9) { glutBitmapCharacter(GLUT_BITMAP_HELVETICA_18, message[i]); }
       if (ch == 1 || ch == 2 || ch == 3) {
           glutBitmapCharacter(GLUT_BITMAP_9_BY_15, message[i]);
       }
   }
   glFlush();
}

//***********************************************************************************
int main(int argc, char** argv)
{
   glutInit(&argc, argv); // optional in our environment
                       //getUserInput();
   glutInitWindowSize(400, 400); // specify a window size
   glutInitWindowPosition(100, 0); // specify a window position
   glutCreateWindow("Simple Text Drawing"); // create a titled window
   myInit(); // setting up
   glutDisplayFunc(myDisplayCallback); // register a callback
   glutKeyboardFunc(myKeyboardCallback);

  

   int sub1 = glutCreateMenu(myMenuCallback);

   glutAddMenuEntry("Red", 1);
   glutAddMenuEntry("Blue", 2);
   glutAddMenuEntry("Green", 3);
   glutCreateMenu(myMenuCallback);
   int sub2 = glutCreateMenu(myMenuCallback);

   glutAddMenuEntry("TIMES_ROMAN_10", 5);
   glutAddMenuEntry("TIMES_ROMAN_24", 6);
   glutAddMenuEntry("HELVETICA_10", 7);
   glutAddMenuEntry("HELVETICA_12", 8);
   glutAddMenuEntry("HELVETICA_18", 9);

   glutCreateMenu(myMenuCallback);
   glutAddSubMenu("Colors", sub1);
   glutAddSubMenu("Fonts", sub2);
  

  

   glutAddMenuEntry("Exit", 4);
   glutAttachMenu(GLUT_RIGHT_BUTTON);

   glutMotionFunc(myMotionCallback);
   glutMainLoop(); // get into an infinite loop
   return 0;
}