gllRotatef does not produce a rotation

Hi, I am trying to rotate a simple square, but I am not seeing nay differences when I call glrotatef. My code:

glClear (GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);
glOrtho (-1,1,-1,1,1,20);
float yRotationAngle = 0.3f;
glTranslatef(0.0f, 0.0f, -5.0f); 
glRotatef (yRotationAngle, 0, 1, 0);
glBegin (GL_QUADS);
		glColor3f (1,0,0); glVertex3f (.75,.75,0);
		glColor3f (0,1,0); glVertex3f (.75,-.75,0);
		glColor3f (0,0,1); glVertex3f (-.75,-.75,0);
		glColor3f (1,1,1); glVertex3f (-.75,.75,0);

	glEnd ();

Outside it, I have this call to glViewport inside X11 setup code:

do {
		XNextEvent (dpy, &xev);
 		if (xev.type == Expose) {
			XGetWindowAttributes (dpy,win,&gwa);
			glViewport (0,0,gwa.width,gwa.height);
			draw ();
			glXSwapBuffers (dpy,win);
		}

Check your glMatrixMode - from your code, it looks like you’re trying to rotate the projection matrix.

If only one matrix is being modified, it won’t matter which one. The distinction only matters for lighting.

But based upon the above code, nothing should be rendered. The glOrtho call maps Z=-1 to the near plane and Z=-20 to the far plane, but the quad is being drawn in the Z=0 plane, so it should fail the near plane test.