You have not setup your projection matrix, so I am guessing it is being draw out of view.
Add this to the start of your display routine
glMatrixMode (GL_PROJECTION); // Tell opengl that we are doing project matrix work
glLoadIdentity(); // Clear the matrix
glOrtho(0.0, 130.0, 0.0, 130.0, 0.0, 60.0); // Setup an Ortho view
glMatrixMode(GL_MODELVIEW); // Tell opengl that we are doing model matrix work. (drawing)
glLoadIdentity(); // Clear the model matrix
I found that glOrtho() 's arguments are very important to make those lines show on screen, I try some set of values, some can work,but some can’t . next day,I decide to realize more on the bizarrerie function.