Please support lsb/rsb deltas when rendering font using Freetype's autohinter

I'm using non-slight auto-hinted fonts (enabled through ~/.fonts.conf) on my desktop and sometimes the results are way bad (e.g. Arial bold 8pt at 96dpi), the letter spacing is very inconsistent.

I checked "ftdiff -r 96 -s 8 arialbd.ttf" and saw that the bad results happen when it's in "no deltas" mode, while in "deltas" mode the auto-hinter's spacing looks very very nice.

I asked about this at Freetype mailing lists and the answer was that qt (among others) needs to implement using the rsb_delta / lsb_delta values to adjust letter spacing when using auto-hinted rendering.

This is very important because: a) Bytecode-hinting is patented and disabled by default in Freetype. b) Some people cannot stand the bytecode-hinting and think it's too ugly (including me). c) The slight auto-hinting is too blurry.
So this leaves the non-slight auto-hinting. Implementing this feature will make it (and the whole Linux/KDE desktop) look very beautiful.

The attached screenshot shows 4 texts - ftdiff bytecode-hinted, ftdiff auto-hinted with deltas, ftdiff auto-hinted without deltas, Qt (which looks the same as ftdiff auto-hinted without deltas, which is obviously not good).

ftdiff's screen was obtained using: "ftdiff -r 96 -s 8 arialbd.ttf" and then pressing "d h r 2 r 1 r".

My ~/.fonts.conf contains the following:

<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>
<match target="font" >
<edit mode="assign" name="rgba" >
<const>none</const>
</edit>
</match>
<match target="font" >
<edit mode="assign" name="hinting" >
<bool>true</bool>
</edit>
</match>
<match target="font" >
<edit mode="assign" name="hintstyle" >
<const>hintfull</const>
</edit>
</match>
<match target="font" >
<edit mode="assign" name="autohint" >
<bool>true</bool>
</edit>
</match>
<match target="font" >
<edit mode="assign" name="antialias" >
<bool>true</bool>
</edit>
</match>
<match target="font" >
<edit mode="assign" name="dpi" >
<double>96</double>
</edit>
</match>

<!-- Accept bitmap fonts -->
<selectfont>
<acceptfont>
<pattern>
<patelt name="scalable"><bool>false</bool></patelt>
</pattern>
</acceptfont>
</selectfont>

</fontconfig>