QGLWidget trouble again

I am trying a simple Qt Application using OpenGL to display a triangle on screen.

But my QGLWidget is not display anything except the background color.

Here is the code :

Code:

intializeGL () { } // Blank for now. not initializing any states
 
resizeGL () {
	if (h==0)			// Prevent A Divide By Zero By
	{
		h=1;			// Making Height Equal One
	}
 
	glViewport(0,0,w,h);	// Reset The Current Viewport
 
	glMatrixMode(GL_PROJECTION);		// Select The Projection Matrix
	glLoadIdentity();					// Reset The Projection Matrix
 
	// Calculate The Aspect Ratio Of The Window
	gluPerspective(45.0f,(GLfloat)w/(GLfloat)h,0.1f,100.0f);
 
	glMatrixMode(GL_MODELVIEW);			// Select The Modelview Matrix
	glLoadIdentity();			        // Reset The Modelview Matrix
}
 
paintGL ()
{
    clearWindow();     // Clear window to black
 
       glColor3f (1.0, 1.0, 1.0);
	glBegin(GL_TRIANGLES);						// Drawing Using Triangles
		glVertex3f( 0.0f, 1.0f, 0.0f);					// Top
		glVertex3f(-1.0f,-1.0f, 0.0f);					// Bottom Left
		glVertex3f( 1.0f,-1.0f, 0.0f);					// Bottom Right
	glEnd();								// Finished Drawing The Triangle
}

It is a simple enough code downloaded from Nehe. But the triangle is not being displayed at all!! can someone help please?