[XeTeX] stacking diacritics without mark-to-mark

[Khaled Hosny]

On Wed, Mar 12, 2014 at 11:21:10PM -0400, Mike Maxwell wrote:
> On 3/12/2014 10:19 PM, Andrew Cunningham wrote:
> >Although personaly I'd consider such a solution a poor hack compared to a well
> >designed font that is fit for purpose.
> 
> I won't disagree.  We've been told by the publisher, who original built the
> font (or more likely subcontracted it) that the problem is a shortcoming of
> their OpenType font files, that could only be eliminated by revising the
> font as a whole.  I'm inclined to tell them to go for it, or else we'll use
> a font that does work (Charis SIL comes to mind).  That would have the
> unfortunate consequence that the first book in our series would use the
> publisher's font (we didn't have the stacked diacritic problem in that
> book), but the rest of the books in the series would use some other font.
> 
> But in order to convince them to make such a change, I need to understand
> better what is involved in revising a font to make mark-to-mark positioning
> work.  I gather that only the diacritics need the two mark-to-mark points
> (top and bottom) to be defined, not every character--correct?

It depends on how general the solution you want, if they are only few
fixed mase+marks sequences, you can use precomposed glyphs and simple
ligaturing (ligature in OpenType fonts can involve diacritics, too).
Mark and mark-to-mark anchors are the most general solution, but it can
be time consuming.

> Is it done at the character level, or at the glyph level?  Does it need to
> be done separately for each point size/ weight/ style that the font
> supports?

It is done on glyph level and it needs to be done for each font file in
the family (if you need it for all of them of course).

> And do those attachment points need to be defined manually, or is there a
> way to automate that process?  Can this be done in a tool like FontForge, or
> does one need specialized tools that only the font manufacturer would have?

They can be semi automated, but it does not save much time in practice.

If possible, you should hire someone to fix the font, he should be able
to examine it and assess what needs to be done. Or you can do it
yourself after learning what it takes, if you are into publishing then I
think it is a good investment in time.

Regards,
Khaled