Re: [ft] Glyph hinting problem with TT hinter

[Werner LEMBERG]

> Werner, I thought you always CC-ed me when things like these came
> up!;-)

Will try to remember!  And thanks for your analysis.

> I see the very same asymmetry onmy rasterizer.

Ha!  I *have* known it!

> Point 25 is the problematic point.  I've calculated it all;
> Microsoft rounds the x-coordinate 895.455782 up to 896 (14.0) in an
> interpolate instruction.  It is then rounded to half a pixel, to
> 14.5 according to the MS interpreter, to 13.5 according to
> FreeType's and mine.  A delta instruction then moves it left to 13.5
> (12.5).  To conclude, the MS rasterizer does faulty rounding here,
> and a delta instruction could have been spared if they had
> implemented it properly.

Well, this is by far the most noticeable bug in the MS TT rasterizer.
It's a tragedy that we know that we are right and MS is wrong but the
rest of the world thinks exactly the opposite :-(

> A related point: Do you keep some registry of these discrepancies?

The `registry' is the mailing list.  And no, I haven't collected the
data yet, and I agree that it would be a good idea to do that, putting
such a file into FreeType's `docs' directory.  Volunteers?

> At some point someone might want to adapt the FreeType interpreter
> to mimic all MS rounding errors.

I fear that too.  Any idea how to do that?


    Werner