Off-by-1 error in drawLine!?

[Michael Schmitt]

Dear developers,

the LyX team is facing another small bug in Qt Win/Free that makes our math 
editor look ugly:

As you have mentioned in the header of qpainter_win.cpp, Windows does not 
draw the end points of a line whereas X11 does so. For that reason, you 
added some special code in drawLine that fixes the discepancy.

However, AFAICS this fix is not correct. If we draw two lines with 
coordinates

  x, y + 3, x, y
  x, y, x + 3, y

I would expect something like

 xxxx
 x
 x
 x

However, Qt Win/Free shows something like this:

 x
 xxxx
 x
 x
 x

That means the end point IS drawn (at least in this particular case).

We would be very happy if you could have a look at this problem. Of course,

  xxxx
       x
       x

(and the two "lower corners") should work as well.

Kind regards,

Michael