[cairo] Font smoothing using anti aliasing

[Karl Tomlinson]

shiplu writes:

> I am trying to smooth text rendering using anti aliasing.
> But its not anti aliased.
>
> See the picture http://tinypic.com/r/2h7dy1i/4
> First line is a png image created using pango and cairo.

This is anti-aliased with CAIRO_ANTIALIAS_GRAY
(from cairo_font_options_set_antialias, I expect).

> Second line is just an html <span> tag. Its in firefox, Ubuntu with Gnome DE.

This looks anti-aliased with CAIRO_ANTIALIAS_SUBPIXEL.  That comes
from screen settings and/or fontconfig settings.