Help on OpenGL in PaintGL

[mickey]

Hi I don't undesrtand a thing: I draw with OpenGl a line and I put it in paintGL (and it is OK):

//initializeGL()
.....
glEnable(GL_BLEND);
glEnable(GL_LINE_SMOOTH);	
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glHint(GL_LINE_SMOOTH_HINT, GL_DONT_CARE);
 
//paintGL
glLineWidth(3.0);
glColor3f(.9f, .1f, .9f); 
glBegin(GL_LINES);
   glNormal3f(0.0f, 1.0f, 1.0f);
   glVertex3f(X, Y, Z);
   glVertex3f(X, Y+3, Z);
glEnd();

//initializeGL()
.....
glEnable(GL_BLEND);
glEnable(GL_LINE_SMOOTH);	
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glHint(GL_LINE_SMOOTH_HINT, GL_DONT_CARE);

//paintGL
glLineWidth(3.0);
glColor3f(.9f, .1f, .9f); 
glBegin(GL_LINES);
   glNormal3f(0.0f, 1.0f, 1.0f);
   glVertex3f(X, Y, Z);
   glVertex3f(X, Y+3, Z);
glEnd();

To copy to clipboard, switch view to plain text mode 

Then I tried to put above instructions inside a function of onother object (scene::drawLine()
And I tried this:

//paintGL()
scene.drawLine(); // this is OK
scene.drawScene();

//paintGL()
scene.drawLine(); // this is OK
scene.drawScene();

To copy to clipboard, switch view to plain text mode 

Scene::drawScene() {
  drawSquare();
}

Scene::drawScene() {
  drawSquare();
}

To copy to clipboard, switch view to plain text mode 

Otherwise:

//paintGL()
scene.drawScene() //my line appear aliased!!!

//paintGL()
scene.drawScene() //my line appear aliased!!!

To copy to clipboard, switch view to plain text mode 

Where:

Scene::drawScene() {
   drawLine();
  drawSquare();
}

Scene::drawScene() {
   drawLine();
  drawSquare();
}

To copy to clipboard, switch view to plain text mode 

Anyone can tell me about this behavior?
Thaks