(Open)GL Sans Triangles

notris.c

/*
	(Open)GL Sans Triangles.

	Mihail Szabolcs, Public Domain.

	Make:
		gcc notris.c -lglut -lGL -lGLU -funroll-loops -O3 -o notris
	
	Run:
		./notris
*/
#include <GL/glut.h>

#define WIDTH		800
#define HEIGHT		600
#define UNUSED(x)	(void)(x)

typedef int rect[4];
typedef float rgba[4];

static rect viewport = {0, };

void draw_rect(rect pos, rgba color)
{
	glPushAttrib(GL_COLOR_BUFFER_BIT | GL_SCISSOR_BIT);

	glScissor(pos[0], viewport[3] - pos[1] - pos[3], pos[2], pos[3]); // invert Y

	glClearColor(color[0], color[1], color[2], color[3]);
	glClear(GL_COLOR_BUFFER_BIT);

	glPopAttrib();
}

void draw(void)
{
	int i, j;
	rect pos = { 0, 0, 100, 100 };
	rgba color = { 0.0f, };

	glClear(GL_COLOR_BUFFER_BIT);

	for(i=0; i<666; i++)
	{
		for(j=0; j<4; j++)
		{
			int c = rand() % 255;
			color[j] = c / 255.0f;
		}

		pos[0] = rand() % viewport[2];
		pos[1] = rand() % viewport[3];

		draw_rect(pos, color);
	}

	glutSwapBuffers();
}

void resize(int w, int h)
{
	glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
	glEnable(GL_SCISSOR_TEST);

	glViewport(0, 0, w, h);

	viewport[2] = w;
	viewport[3] = h;

	glutPostRedisplay();
}

void keyboard(unsigned char key, int x, int y)
{
	UNUSED(key);
	UNUSED(x);
	UNUSED(y);

	exit(0);
}

int main(int argc, char *argv[])
{
	srand(13666);

	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
	glutInitWindowSize(WIDTH, HEIGHT);
	glutCreateWindow("GL Sans Triangles");
	glutDisplayFunc(draw);
	glutReshapeFunc(resize);
	glutIdleFunc(glutPostRedisplay);
	glutKeyboardFunc(keyboard);
	glutMainLoop();

	return 0;
}

notris.png