Comment 32 for bug 398244

I have reported the bug to freedesktop: http://bugs.freedesktop.org/show_bug.cgi?id=22770

-----quoting-------
I'm now attaching a test program that is as minimal as possible and
that shows different behavior with either the vesa or xf86-video-intel
drivers.

However, this isn't actually a driver bug.

Instead, the test program (and wine) are drawing lines with width of
0, (known as "thin lines" in the X protocol description). And such
lines can be implemented with a device-specific algorithm that can
differ from driver to driver[*].

So it's not actually surprising that there are differences
here---that's perfectly allowable. What is a bit surprising is that
the results with the intel driver are equivalent to the results that
would be obtained by using a line width of 1, (where the protocol
specifies an algorithm that defines precisely which pixels must be
affected). I would have expected the vesa driver to match that
behavior.

-----end---------

They give a complete description of the problem and a way to solve it. You can read all the info in: http://bugs.freedesktop.org/show_bug.cgi?id=22770#c14