Re: [ft-devel] New `slight' auto-hinting mode

[Alexei Podtelezhnikov]

On Wed, May 3, 2017 at 5:00 PM, Werner LEMBERG <address@hidden> wrote:
>
>>> However, it would fail miserably if lsb_delta and rsb_delta are
>>> used to adjust integer advance widths by ±1 pixel, as documented in
>>> the FreeType reference.  *This* is what we can't neglect IMHO.
>>
>> With warping out of the way, the light mode becomes a clean case.
>> The left phantom point stays at zero, i.e. lsb_delta is always zero.
>> The right phantom point is simply rounded, i.e. rsb_delta is a
>> rounding residual always between -31 and 32.  Therefore,
>> (prev_rsb_delta - lsb_delta) is always between -31 and 32 and
>> advance is NEVER adjusted in light mode. ∎
>
> I'm not talking about `light' mode!  `lsb_delta' and `rsb_delta' were
> mainly introduced for `normal' (i.e., `strong') auto-hinting.

Brrrr.... Do not confuse me please. Normal hinting and warping for
that matter would not benefit from subpixel positioning. Therefore,
they neither need nor want fractional advance. They stay happily
married to lsb_delta and rsb_delta.

Only light (aka disabled) x-hinting would welcome subpixel positioning
and, hence, fractional advance. I thought that this is clear.