#include <stdio.h>

#include <GL/glut.h>

/* compile command:  gcc gltest.c -g -o gltest -lGL -lglut
 * 
 * must be run using xinit and DRI3 to see the issue.
 * 
 * Program will hang in draw function.
 * 
 * Comment out any one of 
 * 		glutInitWindowPosition
 * 		glutFullScreen
 *		glDrawBuffer(GL_FRONT) 
 * 
 * and it will execute properly.
 * 
 * It will also work if DRI2 is used.
 *		LIBGL_DRI3_DISABLE=1 ./gltest 
 * 
*/

static void
idle(void)
{
	glutPostRedisplay();
}

static void
reshape(int width, int height)
{
	glViewport(0, 0, (GLint) width, (GLint) height);
}

static void
draw(void)
{
	printf("Draw!\n");

	glBegin(GL_QUADS);
		glVertex2f(-1.3333, 1.0);
		glVertex2f(1.3333, 1.0);
		glVertex2f(1.3333, -1.0);
		glVertex2f(-1.3333,	-1.0);
	glEnd();

	glutSwapBuffers();
}

int main(int argc, char *argv[])
{
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE);

	glutInitWindowPosition(0, 0);
	glutInitWindowSize(1024, 768);

	glutCreateWindow("Screen");

	glClearColor(0.0, 0.0, 0.0, 1.0);
	
	glutDisplayFunc(draw);
	glutReshapeFunc(reshape);
	glutIdleFunc(idle);

	glutFullScreen();
	glDrawBuffer(GL_FRONT);

	glutMainLoop();

	return 0;
}