I recently found out that if I render 2 parallel lines (GL_LINE), one of them is 1 pixel shorter than the other at the top. No, it's not numerical precision issue in my code. When I use another video card, the other line (#2) is 1 pixel shorter, but at the bottom. If I try the MS software renderer, line #1 is short, but this time at the bottom.
Is there some issue in line rendering algorithms?
I have already solved the problem with some other means.