rasterization and fragment coordinates for lines

Hi there,

I've been reading a bit about using lines in openGL, but it's not quite clear to me yet how they work in the fragment shader. Specifically I don't understand how the 3d fragment coordinates (or other varying vars) are interpolated when the line has width > 1. A line only has 2 vertices, but basically a rectangular area is rasterized for lines with width > 1 (right?), so... how does the interpolation work then?

Anyone knows how this is implemented?

Thanks!