[HarfBuzz] is opentype crazy

[Behdad Esfahbod]

On 15-03-23 02:10 AM, Martin Hosken wrote:
> Dear All,
> 
> It seems that if I want to insert a glyph (say a dotted circle) between two diacritics, then I can. I can
> 
> sub diac1' diac2 by diac1 dottedcircle
> 
> or something akin to that. But when I do, because diac1 is a mark and not a ligature, harfbuzz resets the advance of my dottedcircle to 0, even though dottedcircle is listed in gdef as being a base. Is this a bug, he asks hopefully?

Different script engines in Uniscribe have different behavior regarding mark
advance zeroing.  HarfBuzz tries to emulate that.  Please test with Uniscribe
and report.  Or if this is for scripts that are not supported by Uniscribe,
please elaborate and we'll see what's going on.  In newer engines (USE), the
plan is to never zero mark advances automatically.

b