c++ program and scope variables [closed] - c++

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I compiled this c++ program with dev-c++ and give "was not declared in this scope" for all variables.
#include <cstdlib> // standard definitions
#include <iostream> // C++ I/O
#include <cstdio> // C I/O (for sprintf)
#include <cmath> // standard definitions
#include <GL/glut.h> // GLUT
#include <GL/glu.h> // GLU
#include <GL/gl.h> // OpenGL
using namespace std; // make std accessible
//-----------------------------------------------------------------------
// Global data
//-----------------------------------------------------------------------
GLint TIMER_DELAY = 10000; // timer delay (10 seconds)
GLfloat RED_RGB[] = {1.0, 0.0, 0.0}; // drawing colors
GLfloat BLUE_RGB[] = {0.0, 0.0, 1.0};
//-----------------------------------------------------------------------
// Global variables
//-----------------------------------------------------------------------
static bool isReversed = false; // draw reversed colors?
//-----------------------------------------------------------------------
// Callbacks
// The global variable "isReversed" describes the drawing state.
// When false, a blue rectangle is drawn on top of red diamond.
// When true the colors are reversed. The "isReversed" variable is
// complemented whenever the left mouse button is clicked or the
// timer goes off (every 10 seconds).
//-----------------------------------------------------------------------
void myReshape(int w, int h) {
cout << "MyReshape called width=" << w << " height=" << h << endl;
glViewport (0, 0, w, h); // update the viewport
glMatrixMode(GL_PROJECTION); // update projection
glLoadIdentity();
gluOrtho2D(0.0, 1.0, 0.0, 1.0); // map unit square to viewport
glMatrixMode(GL_MODELVIEW);
glutPostRedisplay(); // request redisplay
}
// draw diamond and rectangle
void drawObjects(GLfloat* diamColor, GLfloat* rectColor) {
glColor3fv(diamColor); // set diamond color
glBegin(GL_POLYGON); // draw the diamond
glVertex2f(0.90, 0.50);
glVertex2f(0.50, 0.90);
glVertex2f(0.10, 0.50);
glVertex2f(0.50, 0.10);
glEnd();
glColor3fv(rectColor); // set rectangle color
glRectf(0.25, 0.25, 0.75, 0.75); // draw the rectangle
}
void myDisplay(void) { // display callback
cout << "MyDisplay called" << endl;
glClearColor(0.5, 0.5, 0.5, 1.0); // background is gray
glClear(GL_COLOR_BUFFER_BIT); // clear the window
if (isReversed) // draw the objects
drawObjects(BLUE_RGB, RED_RGB);
else
drawObjects(RED_RGB, BLUE_RGB);
glutSwapBuffers(); // swap buffers
}
void myTimer(int id) { // timer callback
cout << "Timer just went off. Reversing colors." << endl;
isReversed = !isReversed; // reverse drawing colors
glutPostRedisplay(); // request redraw
glutTimerFunc(TIMER_DELAY, myTimer, 0); // reset timer for 10 seconds
}
void myMouse(int b, int s, int x, int y) { // mouse click callback
if (s == GLUT_DOWN) {
cout << "Mouse click detected at coordinates x="
<< x << " and y=" << y << endl;
if (b == GLUT_LEFT_BUTTON) {
isReversed = !isReversed;
cout << "Left mouse click. Reversing colors." << endl;
glutPostRedisplay();
}
}
}
// keyboard callback
void myKeyboard(unsigned char c, int x, int y) {
switch (c) { // c is the key that is hit
case 'q': // 'q' means quit
exit(0);
break;
default:
cout << "Hit q to quit. All other characters ignored" << endl;
break;
}
}
//-----------------------------------------------------------------------
// Main program
// This does all the set up for the program. It creates the game
// and then passes control to glut.
//-----------------------------------------------------------------------
int main(int argc, char** argv)
{
cout <<
"Colors swap every 10 seconds.\n"
"Click left mouse button to swap colors.\n" <<
"Try resizing and covering/uncovering the window.\n" <<
"Hit q to quit." << endl;
glutInit(&argc, argv); // OpenGL initializations
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);// double buffering and RGB
glutInitWindowSize(400, 400); // create a 400x400 window
glutInitWindowPosition(0, 0); // ...in the upper left
glutCreateWindow(argv[0]); // create the window
glutDisplayFunc(myDisplay); // setup callbacks
glutReshapeFunc(myReshape);
glutMouseFunc(myMouse);
glutKeyboardFunc(myKeyboard);
glutTimerFunc(TIMER_DELAY, myTimer, 0);
glutMainLoop(); // start it running
return 0; // ANSI C expects this
}
Where is the problem?
[Error] 'glutPostRedisplay' was not declared in this scope
[Error] 'glutSwapBuffers' was not declared in this scope
[Error] 'glutPostRedisplay' was not declared in this scope
[Error] 'glutTimerFunc' was not declared in this scope
[Error] 'GLUT_DOWN' was not declared in this scope
[Error] 'GLUT_LEFT_BUTTON' was not declared in this scope
[Error] 'glutPostRedisplay' was not declared in this scope
etc.

Answer 1

From the GLUT docs here:
The header files for GLUT should be included in GLUT programs with the following include directive (which you have):
#include <GL/glut.h>
Because a very large window system software vendor (who will remain nameless) has an apparent inability to appreciate that OpenGL's API is independent of their window system API, portable ANSI C GLUT programs should not directly include <GL/gl.h> or <GL/glu.h>. Instead, ANSI C GLUT programs should rely on <GL/glut.h> to include the necessary OpenGL and GLU related header files.
If you are not on windows, this may be causing an issue.
It does look like this file is not being included correctly since even the symbolic constants (e.g. for GLUT_DOWN) are not being resolved.

Answer 2

You should look for the header files that declare these functions and variables and include them in this source file.
A good place to start would be this GL directory you seem to be including glut.h from, assuming it exists.

Answer 3

Check building without calling functions in main(). Then try one by one. I think the error is coming from one of your include files.
Are there any classes defined in those files. Check there header files are ok or not. Check for the existence of header files in specified paths.
Then check the namespaces. If you defined a class with a namespace, don't forget to use using namespace namespace_name or specify full qualified name for variables.