[HarfBuzz] behavior of mark-width-zeroing

[Martin Hosken]

Dear Jonathan,

> Our current mark-zeroing code, in zero_mark_widths_by_gdef() and 
> zero_mark_widths_by_unicode(), modifies only the advance of the glyphs, 
> so that they no longer take up any space on the line.
> 
> I'm wondering whether we should also adjust the offset, by subtracting 
> the advance from it before we zero the advance. (Though perhaps only if 
> there's no GPOS positioning?)

How would that affect anchor positioning? Would the offset be ignored or would one need to subtract the advance from all the anchors too?

Yours,
Martin