Display RGB window in linux using OpenGL and Freeglut - linux

Question

I want to create a window covering my whole desktop screen with displaying colors RGB and then VIBGYOR. The color delay should be 1 second.
This is the code I have written but output is not as expected. Can anyone tell me where I am wrong?
#include<GL/freeglut.h>
#include<GL/glut.h>
#include<stdio.h>
void main(int argc, char **argv)
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH );
glutInitWindowSize(1280,1024);
glutCreateWindow("Displays");
glutFullScreen();
glClearColor (1.0, 0.0, 0.0, 0.0); //Red
glClear(GL_COLOR_BUFFER_BIT);
sleep(1);
glClearColor(0,1,0,0); //Green
glClear(GL_COLOR_BUFFER_BIT);
sleep(1);
glClearColor(0,0,1,0);
glClear(GL_COLOR_BUFFER_BIT); //Blue
sleep(1);
glClearColor(0.933, 0.510, 0.933, 0.0); //violet
glClear(GL_COLOR_BUFFER_BIT);
sleep(1);
glClearColor(0.294, 0.000, 0.510, 1); //Indigo
glClear(GL_COLOR_BUFFER_BIT);
sleep(1);
glClearColor(0,0,1,1); //Blue
glClear(GL_COLOR_BUFFER_BIT);
sleep(1);
glClearColor(0,0.502,0,1); //Green
glClear(GL_COLOR_BUFFER_BIT);
sleep(1);
glClearColor(1,1,0,1); //Yellow
glClear(GL_COLOR_BUFFER_BIT);
sleep(1);
glClearColor(1,0.647,0,1); //Orange
glClear(GL_COLOR_BUFFER_BIT);
sleep(1);
glClearColor(1,0,0,1); //Red
glClear(GL_COLOR_BUFFER_BIT);
sleep(1);
glutMainLoop();
}
Thanks.

Answer 1

You're initializing the display mode with GLUT_DOUBLE (double buffering), you need to add gluSwapBuffers() every time you're finished working with the buffer and want to display it.
...
glClearColor(1,0,0,1); //Red
glClear(GL_COLOR_BUFFER_BIT);
glutSwapBuffers();
sleep(1);
...
Difference between single buffered(GLUT_SINGLE) and double buffered drawing(GLUT_DOUBLE)
When using GL_SINGLE, you can picture your code drawing directly to the display.
When using GL_DOUBLE, you can picture having two buffers. One of them is always visible, the other one is not
glut examples
nehe's legacy tutorials
What is the nicest way to close GLUT
void glutLeaveMainLoop ( void );