[HarfBuzz] Glyphs with negative advance width

[Behdad Esfahbod]

Ok, negative vs positive is not the bug.  Uniscribe zeroes mark widths for
Khmer but we don't.  I tried to figure out whether Uniscribe does it by
Unicode category or GDEF, but couldn't build a test font...

At any rate, we need to figure out and do the same.  Jonathan, any comments?

behdad

On 13-06-13 05:31 PM, Olivier Berten wrote:
> After khmer character  ិ(glyph "uni17b7") in the string និង
> 
> Olivier
> 
> 
> 2013/6/13 Behdad Esfahbod <behdad at behdad.org <mailto:behdad at behdad.org>>
> 
>     Ok, I'll take a look.  Can you send me the font?
> 
>     That said, The HarfBuzz API uses signed integers for advance.  So I'm not sure
>     why this is happening.  Where do you observe this behavior again?
> 
>     b
> 
>     On 13-06-13 05:16 PM, Olivier Berten wrote:
>     > Well... Harfbuzz will be the only one behaving that way then...
>     > That font is rendered fine by Adobe, Microsoft, LibreOffice, ... and
>     fontforge
>     > as well as ttx/fontTools gives a negative advance width... I guess this
>     > doesn't push fixing the font ;-)
>     >
>     > Olivier
>     >
>     >
>     > 2013/6/6 Behdad Esfahbod <behdad at behdad.org <mailto:behdad at behdad.org>
>     <mailto:behdad at behdad.org <mailto:behdad at behdad.org>>>
>     >
>     >     Hi Olivier,
>     >
>     >     Thanks for the report.  I'm hesitant to make HarfBuzz return
>     negative advance
>     >     values as that can confuse downstream users.  If this doesn't prove
>     to be a
>     >     major issue, I think we should ignore it for now.
>     >
>     >     behdad
>     >
>     >     On 13-06-01 05:40 PM, Olivier Berten wrote:
>     >     > Hi!
>     >     >
>     >     > Although it isn't complying with the TrueType/OpenType specifications,
>     >     > some fonts have some glyphs with negative advance width.
>     >     >
>     >     > Advance width (in htmx) is defined as USHORT/uint16 but it seems
>     >     > everybody else reads it as SHORT/int16.
>     >     >
>     >     > In the attached font, glyph "uni17b7" (khmer character  ិ) has a
>     >     > negative advance width. You can try it with the string និងសមភាព
>     >     >
>     >     > I wouldn't call this a bug in harfbuzz since it's a font bug but for
>     >     > compatibility reasons, it might be useful to change it...
>     >     >
>     >     > Olivier
>     >     >
>     >     >
>     >     >
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>     >     >
>     >
>     >     --
>     >     behdad
>     >     http://behdad.org/
>     >
>     >
> 
>     --
>     behdad
>     http://behdad.org/
> 
> 

-- 
behdad
http://behdad.org/