[HarfBuzz] font_get_h_extents & font_get_v_extents

[kelvinsthirteen at gmail.com]

> On Jun 26, 2016, at 10:25 PM, Khaled Hosny <khaledhosny at eglug.org> wrote:
> 
>> On Sun, Jun 26, 2016 at 10:05:15PM -0400, Kelvin Ma wrote:
>> How do you get the plain ascent and descent of a font? font_get_h_extents()
>> gives the HHead values of the font, not the regular ascent and descent.
> 
> There are three different settings for ascent and descent in OpenType
> fonts, which one you are after?

The ones that partition the EM square. The ascent and descent should add up to the UPEM value.