[Freetype] Thin polygons

[Giuliano Pochini]

The problem with very thin polygons is still here.
The attached program drawn 80 polygons starting from
the centre of the picture to the edge to show the
problem. You can group the rays in 4 zones:


\  a /
 \  /
d \/
  /\ b
 /  \
/ c  \


a,c - Lines are drawn correctly.

b - Lines have lighter (less covered) peices. They
look "ripped" here and there.

d - Lines have darker (more coveder) pixels. Just the
opposite of b-.

Note that those polygons are 0.1 pixel thin. The
problem doesn't show when the polys are thicker than 1. It
doesn't hurt fonts rendering because the hinter always try
to make gliphs at least 1 pixel thick.

I tried to debug it without success. I suspect it's caused
by a rounding or truncate bug somewhere, but I couldn't
understand how exactly the renderer works :(

[cc -lm -lpng -lfreetype fttest.c ; ./a.out > test.png]

Bye.

fttest.c
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