Enable 2D Over OpenGL

In OpenGL, if we want to 2D only, we can use the Ortho matrix to set ignore the z-list. The following code snippet demo how to do that

void glEnable2D()
{
int vPort[4];

glGetIntegerv(GL_VIEWPORT, vPort);

glMatrixMode(GL_PROJECTION);
glPushMatrix();
glLoadIdentity();

glOrtho(0, vPort[2], 0, vPort[3], -1, 1);
glMatrixMode(GL_MODELVIEW);
glPushMatrix();
glLoadIdentity();
}

void glDisable2D()
{
glMatrixMode(GL_PROJECTION);
glPopMatrix();
glMatrixMode(GL_MODELVIEW);
glPopMatrix();
}