[HarfBuzz] What is the utility of the advances list?

[eduardo]

Cool! Thanks!

On Tue, 29 Oct 2013 10:58:04 +0000, Jonathan Kew wrote:
> On 29/10/13 10:49, eduardo wrote:
>> Is there any reason other than the kerning? Bacause it can be 
>> extracted
>> quite easily using the FT_Get_Kerning function.
>
> Many reasons. GPOS positioning is far more flexible than just kern
> pairs. E.g. there could be a simple kern for "To", but a different
> kern value to be used when the "o" has a combining accent following
> it.
>
> FT_Get_Kerning will only report simple kern pairs from the 'kern'
> table (if present); I don't think it even looks at GPOS, and it
> certainly can't return any meaningful data about more general
> positioning rules.
>
> Maybe you should read up about the OpenType layout process...
>
> http://www.microsoft.com/typography/SpecificationsOverview.mspx
>
>>
>> On Tue, 29 Oct 2013 10:40:59 +0000, Jonathan Kew wrote:
>>> On 29/10/13 10:19, eduardo wrote:
>>>> Hi,
>>>>
>>>> Why does hb return a list of advances when, given a glyph, it can 
>>>> easily
>>>> be extracted from the font? Are the glyph advances context 
>>>> dependant? If
>>>> so, what is a good language/script to see the difference?
>>>>
>>>
>>> Yes, of course they're context-dependent. The simplest example may 
>>> be
>>> kerning. If the GPOS table contains a kern pair for "AV", then the
>>> advances you get from harfbuzz for the 'A' and 'V' glyphs will not 
>>> be
>>> the same as the individual glyph advances you'd find in the font.
>>>
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