Re: [Devel] Bug in ttinterp.c ???

[David Turner]

Hello Rogier,

Rogier van Dalen wrote:
> As I was instructing a TT font I have made, I found FreeType behaving 
> strangely on a few glyphs. It seems to have to do with the MSIRP 
> instruction.
>
> The font is at
> http://home.kabelfoon.nl/~slam/fonts/Legendum_hinted.ttf
> (the instruction code is at 
> http://home.kabelfoon.nl/~slam/fonts/Legendum.tti (This has been 
> produced with my instruction compiler, but the code surely is 
> straightforward enough) )
>
> The capitals I and T look strange with ftview, whereas both the Windows 
> (2000 & 95) scaler and my own, home-grown scaler work as they should. 
> Let's take T (glyph 57).
>
> At g0018, the program calls function 6. At f0398, the MSIRP tries to 
> move a point horizontally at a distance from point 0 in the twilight 
> zone. The y coordinate, however, seems to be set to the twilight point y 
> coordinate, which is 0. It seems to me this has got something to do with 
> the /* XXX: UNDOCUMENTED! behaviour */ part in Ins_MSIRP, which I don't 
> understand at all. This seems to happen at all sizes.
>
> Hopefully someone will be able to see what is wrong or point out what 
> I'm doing wrong...
>
> Rogier
As reported by other posters on the list, this might be a bug in the
TrueType bytecode interpreter that comes with FreeType. Several patches
have been submitted but we need to test them extensively to see if these
do not degrade the rendering of several popular high-quality fonts. I
hope to do this kind of work this or next week..

Best Regards,

- David Turner
- The FreeType Project  (www.freetype.org)


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