[mpeg-OTspec] Creating ReqFeatureIndex in real fonts?

[Thomas Phinney]

Thanks, Adam! I didn't think of ttx for this, but as I use that tool all
the time I am happy to use it for this purpose, now that I know how.

Khaled: Good to know that FontForge can handle it as well.

Cheers,

T

On Thu, Aug 30, 2012 at 2:25 PM, Adam Twardoch (List) <
list.adam at twardoch.com> wrote:

> On 12-08-30 20:49, Thomas Phinney wrote:
> >
> >
> > I have a different question about ReqFeatureIndex.
> >
> > I am collaborating on a special-purpose font, whose entire purpose is
> > tied up in having ligatures work. It is useless without them. It seems
> > to me like as a practical matter, ReqFeatureIndex would be a good way
> > to make those ligatures work in more environments, at least in
> > versions of Windows and Office that might not otherwise support those
> > ligatures.
> > What tools actually support making fonts with ReqFeatureIndex? I'm
> > happy using FontLab Studio. AFDKO would not be the ideal workflow for
> > this project, but is possible. I would be fine with learning VOLT. I'd
> > use FontForge if scary weapons were pointed at me, or I had no
> > alternative.
> You'll certainly be able to use FontTools/TTX and set the
> ReqFeatureIndex in the post-production step.
>
> Regardless of which tool you use to build the GSUB and GPOS tables, you
> would then run
>
>   ttx -t GSUB myfont.otf
>
> which will yield you a "myfont.ttx" file which will contain the GSUB
> table. Inside, you'll find something like this:
>
>   <GSUB>
>     <Version value="1.0"/>
>     <ScriptList>
>       <ScriptRecord index="0">
>         <ScriptTag value="latn"/>
>         <Script>
>           <DefaultLangSys>
>             <ReqFeatureIndex value="65535"/>
>             <FeatureIndex index="0" value="7"/>
>             <FeatureIndex index="1" value="6"/>
>             <FeatureIndex index="2" value="12"/>
>             <FeatureIndex index="3" value="25"/>
>             ...
>             </LangSys>
>           </LangSysRecord>
>         </Script>
>       </ScriptRecord>
>     </ScriptList>
>     <FeatureList>
>       ...
>       <FeatureRecord index="12">
>         <FeatureTag value="liga"/>
>         <Feature>
>           <LookupListIndex index="0" value="37"/>
>           <LookupListIndex index="1" value="38"/>
>         </Feature>
>       </FeatureRecord>
>
> If you change the line
>             <ReqFeatureIndex value="65535"/>
> to
>             <ReqFeatureIndex value="2"/>
> then FeatureIndex 2 will be the ReqFeatureIndex. FeatureIndex 2 points
> to FeatureRecord 12, and FeatureRecord 2 implements the "liga" feature
> with two lookups.
>
> So basically, you'll need to locate the FeatureRecord for the feature
> entry that you're interested in, then look up its reference in the
> appropriate languagesystem list, and then just set the FeatureIndex of
> that record as the ReqFeatureIndex for that languagesystem.
>
> It's relatively easy.
>
> Then you just run
>
>   ttf -m myfont.otf myfont.ttx
>
> and you'll get myfont#1.otf, which will have the modified GSUB table.
>
> Best,
> Adam
>
> --
>
> May success attend your efforts,
> -- Adam Twardoch
> (Remove "list." from e-mail address to contact me directly.)
>
>


-- 
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