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

[Werner LEMBERG]

>> . NORMAL currently means full auto-hinting, i.e., hinting along
>>   both the horizontal and vertical axes.  I believe we can't change
>>   that.
>
> I see warping is a kind of hinting where shifting/scaling is tweaked
> for all segments at once rather than for each segment individually.
> Therefore, warping option would replace normal hinting, of course.

I seem to understand now.  Let me summarize to see whether this is
really true :-)

  . Right now, warping is activated with AF_CONFIG_OPTION_USE_WARPER.
    If compiled in, we have the `warp' auto-hinter property that adds
    warping to the light auto-hinting mode (which doesn't do any
    horizontal hinting otherwise).

  . You suggest that if AF_CONFIG_OPTION_USE_WARPER is on, the normal
    auto-hinting mode's horizontal hinting gets replaced with warping,
    again to be controllable by the `warp' auto-hinter property.
    `light' auto-hinting is thus no longer affected by warping.

This sounds like a good idea.

>> For LIGHT, I'm not sure that we can do that for backward
>> compatibility...
>
> - If someone was using lsb_delta and rsb_delta correctly, then the
>   fractional part just shifts from rsb_delta to fractional advance
>   width, while lsb_delta is always 0 in LIGHT. There should not be
>   no changes in layout whatsoever.

What you describe is the case of using lsb_delta and rsb_delta to get
fractional advance widths.  I agree that this use case would work.

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.


    Werner