OpenGL newbie - why won't these lines display properly?

cscooper

I need to make it so part of my Qml view is "taken over" by some non-Qt OpenGL rendering, and I was having issues getting a texture to display properly so I thought I would just draw a line and get that to work before moving on to more complicated code.

I took the Squircle sample code ( http://qt-project.org/doc/qt-5/qtquick-scenegraph-openglunderqml-example.html ) and modified it slightly so it would draw in a specified portion of the screen (instead of the entire screen) and that is working perfectly. Then, I modified just the renderer::paint() function to initially draw three green lines, and after 2 seconds to instead draw one blue line:

@void CtRenderer::paint()
{
static int n = 0;

if (n == 0)
{
    glViewport(m_rect.x() + 10, m_rect.y() + 10, m_rect.width() - 20, m_rect.height() - 20);

    glEnable(GL_SCISSOR_TEST);
    glScissor(m_rect.x() + 10, m_rect.y() + 10, m_rect.width() - 20, m_rect.height() - 20);

    glDisable(GL_DEPTH_TEST);
    glDisable(GL_LIGHTING);

    // glClearColor(1, 0, 0, 1);
    // glClear(GL_COLOR_BUFFER_BIT);

    glLineWidth(10);
    glColor4f(0.0, 1.0, 0.0, 1);
    glBegin(GL_LINES);
    glVertex3f(0.0, 0.0, 1);        glVertex3f(1, 0.5, 1);
    glVertex3f(0.0, 0.0, 1);        glVertex3f(0.5, 0.5, 1);
    glVertex3f(0.0, 0.0, 1);        glVertex3f(0.5, 1, 1);
    glEnd();
}
else if (n == 120)
{
    glViewport(m_rect.x() + 10, m_rect.y() + 10, m_rect.width() - 20, m_rect.height() - 20);

    glEnable(GL_SCISSOR_TEST);
    glScissor(m_rect.x() + 10, m_rect.y() + 10, m_rect.width() - 20, m_rect.height() - 20);

    glDisable(GL_DEPTH_TEST);
    glDisable(GL_LIGHTING);

    // glClearColor(1, 0, 0, 1);
    // glClear(GL_COLOR_BUFFER_BIT);

    glLineWidth(10);
    glColor4f(0.0, 0.0, 1.0, 1);
    glBegin(GL_LINES);
    glVertex3f(0.0, 0.0, 1);        glVertex3f(0.4, 0.8, 1);
    glEnd();

}
n++;

return;

}@

What I get instead are three gray lines that flicker continuously and never change to being a single line. I'm relatively new to OpenGL, so I'm probably doing something stupid. Can someone point me in the right direction with this code?

Thanks!
Chris