[HarfBuzz] A problem in thai shaper

Khaled Hosny khaledhosny at eglug.org
Tue Apr 17 15:47:08 PDT 2012

On Tue, Apr 17, 2012 at 05:10:37AM +0200, Khaled Hosny wrote:
> On Mon, Apr 16, 2012 at 09:08:49PM -0400, Behdad Esfahbod wrote:
> > > Problem 2:
> > > 
> > > When there is no consonant exist, the dotted circle should be inserted as base
> > > character.  The logic should be the first step for the shaping engine to find
> > > the invalid combing marks. Refer to
> > > http://www.microsoft.com/typography/otfntdev/thaiot/shaping.aspx#comb
> > 
> > Right.  We do not handle invalid combining marks yet.  That's something I want
> > to do at some point but it's not high priority.
> I don't know about Thai, but the handling of "invalid" Arabic combining
> marks in Uniscribe is completely brain dead and a real PITA and I'd
> really like not to see HarfBuzz going there, a shaping engine is not a
> spell checker and should not enforce any input pattern.
> http://www.microsoft.com/typography/OpenType%20Dev/arabic/shaping.mspx#invalid

Incidentally, I came across this Typophile post, which is one example of
why this "invalid" mark handling is not really a good idea:


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