Open GL compiles on Codelite Windows 7, but no ouput displayed - c++

Question

I am trying this sample open gl program on my codelite ide.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <GL/glut.h>
GLenum doubleBuffer;
GLint thing1, thing2;
static void Init(void)
{
glClearColor(0.0, 0.0, 0.0, 0.0);
glClearAccum(0.0, 0.0, 0.0, 0.0);
thing1 = glGenLists(1);
glNewList(thing1, GL_COMPILE);
glColor3f(1.0, 0.0, 0.0);
glRectf(-1.0, -1.0, 1.0, 0.0);
glEndList();
thing2 = glGenLists(1);
glNewList(thing2, GL_COMPILE);
glColor3f(0.0, 1.0, 0.0);
glRectf(0.0, -1.0, 1.0, 1.0);
glEndList();
}
static void Reshape(int width, int height)
{
glViewport(0, 0, width, height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}
static void Key(unsigned char key, int x, int y)
{
switch (key) {
case '1':
glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
glutPostRedisplay();
break;
case '2':
glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
glutPostRedisplay();
break;
case 27:
exit(0);
}
}
static void Draw(void)
{
glPushMatrix();
glScalef(0.8, 0.8, 1.0);
glClear(GL_COLOR_BUFFER_BIT);
glCallList(thing1);
glAccum(GL_LOAD, 0.5);
glClear(GL_COLOR_BUFFER_BIT);
glCallList(thing2);
glAccum(GL_ACCUM, 0.5);
glAccum(GL_RETURN, 1.0);
glPopMatrix();
if (doubleBuffer) {
glutSwapBuffers();
} else {
glFlush();
}
}
static void Args(int argc, char **argv)
{
GLint i;
doubleBuffer = GL_FALSE;
for (i = 1; i < argc; i++) {
if (strcmp(argv[i], "-sb") == 0) {
doubleBuffer = GL_FALSE;
} else if (strcmp(argv[i], "-db") == 0) {
doubleBuffer = GL_TRUE;
}
}
}
int main(int argc, char **argv)
{
GLenum type;
glutInit(&argc, argv);
Args(argc, argv);
type = GLUT_RGB | GLUT_ACCUM;
type |= (doubleBuffer) ? GLUT_DOUBLE : GLUT_SINGLE;
glutInitDisplayMode(type);
glutInitWindowSize(300, 300);
glutCreateWindow("Accum Test");
Init();
glutReshapeFunc(Reshape);
glutKeyboardFunc(Key);
glutDisplayFunc(Draw);
glutMainLoop();
}
Program compiles fine on my machine, when tried to run it just output press any key to continue and program exits after key is pressed.
What I am missing ?

Answer 1

What command line arguments have you passed? You have no choice but to use -db for reasons I will explain.
In Windows 7, you cannot draw a single-buffered window because the window manager makes a copy of the framebuffer when you swap buffers and that is what it displays (composites). Without swapping buffers, nothing will ever be displayed. This modern window system design prevents painting partially completed frames, but it mandates double-buffered rendering.
In fact, you should re-write your software so that it defaults to double-buffered rendering unless you specify a command line argument instead of the other way around. This issue affects other platforms besides modern Windows (Vista and newer).