[NTG-context] issue with optical bounds (OpenType)

Hans Hagen j.hagen at xs4all.nl
Mon Dec 10 10:51:58 CET 2018


On 12/9/2018 8:54 PM, Pablo Rodriguez wrote:
> On 12/9/18 6:53 PM, Hans Hagen wrote:
>> On 12/9/2018 5:35 PM, Pablo Rodriguez wrote:
>>> [...]
>>> -Is there any way that I can apply pure raw lfbd/rtbd values to
>>> protrusion with no other protrusion calculation at all in opbd?
>>
>> you can create your own vectors if you want
> 
> My own vectors wouldn’t solve the issue, because the variable would be:
> 
>     lfbd(Ὧ) = glyph.width(Ω) - glyph.width(Ὧ)
> 
> I need to place glyphs accurately, not characters. Character dimensions
> wouldn’t help to get hanging diacritics.

well, these dimensions are available so one could use them in 
constructing additional lfbd feature specifications (add f eatures 
runtime)

>>> -In order to avoid editing all the Greek fonts to get hanging
>>> diacritics: is there any way to replicate the lfbd feature with
>>> "fonts.handlers.otf.addfeature"?
>>
>> probably with some lua magic one can do a lot but these are typical
>> things i do when i need them (also because one needs to check the whole
>> of unicode and cook up categories, this kind of stuff is: do it all
>> robust and well or don't do it; also one doesn't know how consistent
>> font designs are)
> 
> The variable is so simple that the glyph with diacritical marks should
> be placed in the beginning of the line as it had no such marks.

the mechanism is more complex: the linebreak algorithm has to take this 
into account (both ends of a potential line) and also look over e.g. par 
starts and so

Hans

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