[HarfBuzz] How to increase harfbuzz numerical precision

[Kelvin Ma]

Helps to get users of your library if you don’t act like everyone trying to
learn it is already an expert on all the hidden intricacies of it.


P.S. font_get_ppem() returns zero for every font. Maybe I am using it wrong
but I wouldn’t know, I didn’t write the thing.

hb_font = hb.font_create(hb_face)
hb.font_set_scale(hb_font, projection['fontsize'], projection['fontsize'])
hb.ot_font_set_funcs(hb_font)
print(hb.font_get_ppem(hb_font))

>>> (x_ppem=0, y_ppem=0)

On Tue, Jun 28, 2016 at 7:01 PM, Behdad Esfahbod <behdad at behdad.org> wrote:

> On Tue, Jun 28, 2016 at 6:56 PM, Kelvin Ma <kelvinsthirteen at gmail.com>
> wrote:
>
>> No, i’m asking why harfbuzz has the concept of multiple fonts per face,
>> if that concept is useless in practice.
>>
>
> Helps if you ask without baking your own presumptions into the question.
> hb_font_t exists to hold all "configuration" needed.  Adding that to
> hb_face_t would have made the face unusable from multiple threads.
>
> Such configuration is mainly the scale, and indeed, many clients shape
> with one font all the time.  But there are other stuff.  ppem is the other
> one.  When "OpenType GX" variation fonts become a thing, the variation
> parameters will also be set on hb_font_t.
>
>
>> On Tue, Jun 28, 2016 at 6:54 PM, Behdad Esfahbod <behdad at behdad.org>
>> wrote:
>>
>>> You can't have both.  Pick which you like.
>>>
>>> On Tue, Jun 28, 2016 at 6:43 PM, Kelvin Ma <kelvinsthirteen at gmail.com>
>>> wrote:
>>>
>>>> so that’s the only way huh…
>>>> doesn’t that kind of defeat the purpose of hb.font_create() and having
>>>> many scaled versions of the same font? You would only ever need one font of
>>>> each face, scaled to the UPEM, if the fontsize was to be applied externally
>>>> after shaping already occurred.
>>>>
>>>> On Tue, Jun 28, 2016 at 5:51 PM, Behdad Esfahbod <behdad at behdad.org>
>>>> wrote:
>>>>
>>>>> HarfBuzz coordinates work in a int32 space.  You are free to set
>>>>> whatever scales you want on the font.  For example, use 6 or 8 or 10 or 16
>>>>> bits of sub-pixel precision by multiplying your scale by a number.
>>>>>
>>>>> On Tue, Jun 28, 2016 at 4:57 PM, Kelvin Ma <kelvinsthirteen at gmail.com>
>>>>> wrote:
>>>>>
>>>>>> It appears that harfbuzz rounds all decimals to integers when giving
>>>>>> glyph advances and offsets. This is causing some ugly misalignment problems
>>>>>> in arabic shaping, as well as latin cursive fonts. (see pictures)
>>>>>>
>>>>>> [image: Inline image 1]
>>>>>>
>>>>>> [image: Inline image 2]
>>>>>>
>>>>>> [image: Inline image 3]
>>>>>> How do I get harfbuzz to preserve the floats?
>>>>>>
>>>>>> _______________________________________________
>>>>>> HarfBuzz mailing list
>>>>>> HarfBuzz at lists.freedesktop.org
>>>>>> https://lists.freedesktop.org/mailman/listinfo/harfbuzz
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> behdad
>>>>> http://behdad.org/
>>>>>
>>>>
>>>>
>>>
>>>
>>> --
>>> behdad
>>> http://behdad.org/
>>>
>>
>>
>
>
> --
> behdad
> http://behdad.org/
>
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