Stencil buffer problem

Just trying to use the stencil buffer for the first and and my first test worked straight away. To write to the stencil I used

     // Clear the stencil to 0
    // INCRease stencil to non-zero when draw
    glStencilOp(GL_INCR, GL_INCR, GL_INCR);
    // NEVER pass so nothing appears on screen
    glStencilFunc(GL_NEVER, 0x0, 0x0);

    // Single glDrawArrays call to draw the stencil shape I want.

    glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);

Then to render my image

        // Only show parts which where stencil is ZERO
        glStencilFunc(GL_EQUAL, 0, 0xffffffff);
        glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);

and I got no image for the parts where I drew to the stencil.

However, I then changed the GL_EQUAL to GL_NOTEQUAL and my entire image was visible. I thought it would invert the result i.e. I’d only see the image for where I drew to the stencil.

I’m obviously not unstanding something fundemental about the stencil test.

Solved. Like an idiot I’d put the call to turn off the stencil test in the wrong place. What I don’t understand though is why it worked at all.